Astronomy & Astrophysics's topics - tribe.net

anti-asteroid technology plan

2008-10-06T22:09:19Z

anti-asteroid technology plan

Planetary Defense against incursions from the Kupier Belt

The extreme chaos and mass trajectory potential of the belt represents a grave threat.
Slingshot balistic nickle asteroids have pounded Earth many times.
Our opportunity in self-defense only grows with new technology and planning available.
The models of distributed networking and nanobot self-organizing systems may provide an important security option.

Explosive binary compounds already exist, and represent terrible destructive power.
That potential, combined as a cloud of interdependent nanobot agents, could represent the ability to set up shear loads and cracking in space.
The relatively simple plan to use space based beams and ordinance to intercept extreme velocity threats, could be enhanced.

Launched from a moon or a station for the purpose, distributed clouds of binary nanobots may in fact represent our only opportunity to defend our commitment to the homeostatic environment as we know it.

posted in Astronomy & Astrophysics - 5 replies

Some solar flares may be caused by dark matter

2008-08-25T23:40:53Z

15:36 22 August 2008
NewScientist.com news service
Anil Ananthaswamy

Some solar flares may be caused by dark matter particles called axions spewing out from the center of the Sun, new calculations suggest.

Solar flares are sudden changes in the Sun's brightness thought to be caused when twisted magnetic fields on the Sun snap and reconnect explosively.

But they could also be caused by dark matter, the mysterious entity that makes up most of the universe's mass – if it is made up of theoretical particles called axions.

Axions, http://space.newscientist.com/article/mg19926664.900-hypothetical-particle-presents-a-fresh-test-for-inflation.html , were proposed in the 1970s to help explain the mystery of why our universe is made mostly of matter and not antimatter. They should be produced deep inside the Sun and should interact with some of the Sun's magnetic fields as they stream outwards, producing flares that are bright at X-ray wavelengths.

Physicists had predicted that these axion-generated flares would have certain traits – the flares' X-ray photons were expected to travel radially outwards from the Sun, for example. But observations showed they came out at all angles.

Now, researchers led by Konstantin Zioutas of the University of Patras in Greece, say they have solved such discrepancies, http://lanl.arxiv.org/abs/0808.1545 .

In their scenario, the first X-rays produced by axions would ionize surrounding matter. The electrons freed in the process would then cause subsequent X-rays to scatter, explaining why the photons show no preferred direction when leaving the Sun.

Zioutas says analyzing flares in detail would indicate the depths at which they formed in the Sun. That in turn could shed light on how massive axions are, since their mass is related to the density of the solar plasma at which they would be able to produce X-ray photons.

With the axion's mass, cosmologists could use estimates of how many were produced in the early universe to figure out what fraction of dark matter is made of axions and what is made of other candidates, such as particles known as WIMPs, http://www.newscientist.com/channel/fundamentals/mg19926702.600-has-dark-matters-telltale-signature-been-spotted.html .

The new study is more qualitative than quantitative, says Konrad Dennerl of the Max Planck Institute for Extraterrestrial Physics at Garching, Germany. But he says that even though solar flares can mostly be explained by conventional physics, they are still somewhat of a mystery.
"What we see may well be a superposition of different effects," he says. "There is room for speculation, and this is one specific speculation of how it could be."

From : http://space.newscientist.com/article/dn14588-some-solar-flares-may-be-caused-by-dark-matter.html

posted in Astronomy & Astrophysics - 5 replies

Sloan Digital Sky Survey

2008-08-22T14:58:53Z

Survey: Changing How Scientists –and the Public - Do Astronomy
Written by Nancy Atkinson

http://www.universetoday.com/2008/08/21/sloan-digital-sky-survey-changing-how-scientists-%e2%80%93and-the-public-do-astronomy/

Recently we've had articles on Universe Today that have discussed the outer Milky Way Galaxy, dark matter, and the discovery of a new minor planet. These articles have a common thread: The discoveries all come from the Sloan Digital Sky Survey (SDSS). If you aren't familiar with SDSS, it encompasses a comprehensive survey lasting more than eight years, which has so far covered more than one-quarter of the sky. Using a dedicated 2.5 meter telescope equipped with a 125- megapixel digital camera and spectrographs that can observe 640 stars and galaxies at a time, the SDSS has created terabytes of data that include thousands of deep, multi-color images. It's also measured the distances to nearly one million galaxies and over 100,000 quasars to create the largest ever three-dimensional maps of cosmic structure. The SDSS archive represents a thousand-fold increase in the total amount of data that astronomers have collected to date. But almost equally impressive is the easy-to-use interface that allows anyone in the world to access the SDSS data online. Whether you are a research astronomer looking for information to help solve a cosmological puzzle or an armchair astronomy enthusiast who just likes looking at pretty pictures of the universe, SDSS is at your disposal.

Astronomers gathered in Chicago earlier this week to celebrate the accomplishments and look ahead to the future of SDSS. "What amazes me is the huge range of the discoveries that have come from SDSS data," said SDSS-II Director Richard Kron, an astronomer at the University of Chicago and Fermilab. "We designed it primarily as a survey to map the distribution of galaxies and quasars, but it's also had a huge impact on the study of stars, the structure of our own Galaxy, and even solar system objects."

SDSS has found new dwarf companion galaxies to the Milky Way, confirmed Einstein's prediction of cosmic magnification, and observed the largest known structures in the universe. The new survey, SDSS-III, will continue to expand our horizons with new studies of the structure and origins of the Milky Way Galaxy and the nature of dark energy.

SDSS was undertaken to update the database of information about the sky with current technology. The previous comprehensive guide to the heavens was the Palomar Sky Survey that was conducted in the 1950's and used glass photographic plates to store the data.

Not only has SDSS updated the technology, but it has changed the way astronomers do business. Astronomers who are doing research or have a question can look at the existing data in SDSS rather than having to pore through the sky, taking their own data with hard-to-get telescope time.

Dr. Pamela Gay, professor at Southern Illinois University Edwardsville and host of the Astronomy Cast podcast said SDSS not only helps her research, but enhances her work in the classroom. "It's a wonderful project," she said. "I'm at a small state university and while I did my dissertation on galaxies, when I landed at a state school, I thought I'd never be able to do this (study galaxies) again because I don't have access to a large telescope. But because of the Sloan Digital Sky Survey, and because of the easy to use tools where I can say to my undergraduate students, 'go find all the data on these clusters,' it's possible for people at small schools to do amazing, amazing research and explore the entire universe."

SDSS also powers the popular Galaxy Zoo website, where anyone in the world can help classify galaxies via the internet. From the work done by the public from their home computers, Galaxy Zoo has submitted peer reviewed research articles to astronomical journals.

Visit the SDSS website to take a look at the images and discoveries made possible by this comprehensive survey. The Sky Server interface on the SDSS website provides the tools you need to start perusing the universe, and has educational activities for teachers and students as well.

Jim Gunn, SDSS Project Scientist from Princeton University, who has guided the project since its inception said that more than any single discovery, he is proud of the quality and scope of the SDSS data sets. "Visible light is where we understand the universe best, but when we began the SDSS, there were no sensitive, well characterized, visible-light catalogs that covered a large area of sky," he said. "Now we have multi-color images of 300 million celestial objects, 3-dimensional maps and detailed properties of well over a million of them, and it's all publicly available online. That changes everything."

posted in Astronomy & Astrophysics - 1 reply

Galactic 'spaghetti monster' powered by magnetic fields

2008-08-21T17:12:05Z

20:07 20 August 2008
NewScientist.com news service
Rachel Courtland

Long-lived magnetic fields are sustaining a mammoth network of spaghetti-like gas filaments around a black hole, a new study suggests. Previously, it was not clear what prevented the delicate filaments from being destroyed by competing gravitational forces.

The black hole lies at the heart of a large galaxy known as NGC 1275, which itself lies near the centre of a cluster of galaxies called Perseus.

As the black hole sucks in gas from its surroundings, it powers jets of matter that produce bubbles of energetic particles in the surrounding cluster gas, http://tribes.tribe.net/astronomyastrophysics/thread/bcb41e8f-80ce-4df2-9bb1-bb31d5c6582a . As these bubbles grow and rise, cooled gas from NGC 1275's core gets drawn into long tendrils in their wake, like the strings that trail behind balloons.

Until now, no one was sure quite how old these gas filaments were or how they avoided being torn apart by the galaxy cluster's immense gravitational forces. "Quite what the filaments are and how they are produced hasn't been known," says study author Andrew Fabian of Cambridge University in the UK.

But Hubble Space Telescope images used in the study, the most detailed yet taken of the galaxy, are changing that.

They show the gas filaments seem to be made up of a number of thin threads. These threads are so tenuous that magnetic fields are the only thing that can protect them from being destroyed, says Fabian.

Stabilizing effect

The magnetic fields, thought to get their start close to NGC 1275's black hole, hold onto the filaments because they wield influence over charged particles – such as protons and electrons – in the filaments' gas.

A typical thread is about 20,000 light years long, and the filaments extend over a region spanning 300,000 light years. Based on their speed, they seem to have persisted for more than 100 million years.

Fabian and colleagues calculate that they are maintained by magnetic fields that are only 0.01% as strong as the field on the Earth's surface.

The fields are powerful enough to prevent the filament gas – which measures just a few hundred degrees Celsius – from evaporating away into the 40 million °C sauna of surrounding cluster gas.

The magnetic fields not only prevent the filaments from being torn apart by gravitational forces, they may also stabilize the gas, preventing it from collapsing to form stars.

Stunted growth

This inhibited star formation could help resolve an outstanding issue in cosmology: why astronomers see fewer high-mass galaxies than models predict, says Patrick Ogle of Caltech.

Astronomers believe some massive galaxies are prevented from growing even larger because they contain black holes that, like the one at the heart of NGC 1275, are devouring their surroundings and spewing out jets.

These jets are thought to heat up the galaxies' gas so much that it expands right into space, http://space.newscientist.com/article/dn7132-red-and-dead-galaxies-surprise-astronomers.html , thereby starving the galaxies of star-forming material.

But if some galaxies also funnel gas into filaments that prevent new stars from forming, that mechanism may also stunt the galaxies' growth. "It may explain why these galaxies don't grow bigger than they do," Ogle told New Scientist.

Journal reference: Nature, http://www.nature.com/index.html , (vol 454, p 968)

Original Publication: http://space.newscientist.com/channel/astronomy/dn14573-galactic-spaghetti-monster-powered-by-magnetic-fields.html?feedId=astronomy_rss20

posted in Astronomy & Astrophysics - 0 replies

Black hole's colossal sphere of influence revealed

2008-08-21T17:05:35Z

22:55 01 December 2005
NewScientist.com news service
Kelly Young

The observation of colossal bubbles of energetic particles in space by NASA’s Chandra X-ray Observatory has revealed the enormous sphere of influence exerted by some black holes. This vast reach can also slow down the growth of surrounding galaxies by slowing star formation.

“Direct observational evidence for a black hole having a large influence has not been forthcoming till now,” says Andrew Fabian, at Cambridge University, UK and leader of the study. “But we think this image really shows something going on.”

The team used Chandra to find huge energetic bubbles spanning 300,000 light years. The bubbles seem to be squirted out by jets near a super massive black hole in the Perseus cluster. The size of the bubbles suggests the black hole may have been producing them for 100 million years.

“In relative terms, it is as if a heat source the size of a fingernail affects the behavior of a region the size of Earth,” Fabian explains.

Sound waves

Although bigger bubbles have been seen around other black holes, this is the first time that a telescope has spotted a whole sequence of expanding plumes spaced at intervals. In the image, the bubbles are the darker regions.

This black hole is pulling in large amounts of gas from the surrounding cluster of galaxies. Some of that gas is then ejected back out in high speed jets, forming the bubbles. This venting generates sound waves that heat up the surrounding area.

The heat prevents the material in the nearby galaxies from cooling down and coalescing, stifling star growth. This effect has slowed the growth of the cluster’s massive central galaxy, NGC 1275.

“Until 1970 people thought that stars were the most influential elements in the universe,” says Fabian. “This study is part of a growing realization that sometimes black holes dominate far more than stars: in fact they have the power to stifle the formation of stars.”

This was the longest X-ray observation ever taken of a galaxy cluster, with Chandra peering at the region for more than 11 days.

The study was be published in the Monthly Notices of the Royal Astronomical Society.

Original Publication: http://space.newscientist.com/article/dn8405-black-holes-colossal-sphere-of-influence-revealed.html

posted in Astronomy & Astrophysics - 0 replies

Planets without metal cores may be bad for life

2008-08-21T07:43:26Z

15:07 20 August 2008
NewScientist.com news service
Ker Than

Some planets beyond our solar system might be rocky like Earth, but lack its gooey metallic middle, a new study suggests. Such 'coreless' terrestrial planets would not have magnetic fields, which would make them inhospitable to life as we know it.

Rocky planets were once thought to consist of three main layers: a thin solid crust, a viscous, rocky mantle and a solid or molten iron core.

This layering, or differentiation, is thought to have occurred early in the solar system's history, when collisions between rocky bodies and the decay of radioactive isotopes melted the interiors of large objects, allowing dense material to settle towards their centers.

But exoplanet discoveries have revealed a menagerie of diverse worlds, http://space.newscientist.com/article/dn12685-scifi-model-worlds-aid-planet-classification.html . Now, Linda Elkins-Tanton and Sara Seager of MIT describe how another planetary oddity might form: coreless rocky planets.

Such planets might differentiate into layers of different density but not form a core – essentially making them giant silicate mantles.

One way this could happen is if the planet was born in a very water-rich environment, such as the icy regions at large orbital distances from Sun-like stars.

The iron could interact with water, forming iron oxide, faster than it would fall to the center of the planet. "If the iron reacts with water, then it will be locked away with other minerals and won't reach the core as metallic iron," Seager told New Scientist.

Alien life

Currently, astronomers have no clear way of determining whether a distant rocky exoplanet has a core, Seager said. That's because telescopes are not yet good enough to image such small planets, much less study their chemical composition.

But studying the planet's parent star may provide hints about the existence of its core, suggests Diana Valencia of Harvard University, who was not involved in the study. "If we look at the star, we will know the iron-silicate ratio and some of the chemistry that was present while these planets were forming," she told New Scientist.

One thing that is certain is that coreless planets will not have magnetic fields.

Earth's magnetic field is generated by molten iron circulating in its core. It shields, http://www.newscientist.com/article/dn11545-earths-magnetic-field-grew-strong-at-a-young-age.html , life on Earth from harmful charged particles from space called cosmic rays. "If we got nailed by cosmic rays, it would cause us a lot of [genetic] mutations," Seager says.

But Seager says a magnetic field may not be crucial for alien life. "I always like to think that life is a lot smarter than we are and that it can exist in many different places in many different ways, http://space.newscientist.com/article/mg19426071.200-life--but-not-as-we-know-it.html ," Seager says.

Journal reference: Astrophysical Journal, http://www.journals.uchicago.edu/toc/apj/current?cookieSet=1 , (forthcoming)

Original Publication: http://space.newscientist.com/channel/astronomy/dn14571-coreless-planets-may-be-bad-for-life.html?feedId=astronomy_rss20

posted in Astronomy & Astrophysics - 2 replies

Why is the Moon the same size as the Sun as seen from Earth?

2008-08-21T00:56:31Z

I remember reading that the Moon used to be much closer to the Earth (How do they know that? Ancient Indian and Egyptian reports of surfing conditions?). And the reason the same side of the Moon always faces us is because it dissipates energy at the slowest rate. Is the present orbit of the Moon due to energetic considerations? Or is it inexorably on its (asymptotic) way to infinity?

posted in Astronomy & Astrophysics - 47 replies

Middleweight Black Holes Nearly Ruled Out

2008-08-20T23:16:25Z

By Space.com Staff

There is no middle ground when it comes to black holes, which tend instead to be either petite or gargantuan, a new study suggests.

Black holes are known to exist in two classes: The stellar variety, http://www.space.com/scienceastronomy/080401-smallest-blackhole.html , result from exploded massive stars and typically pack the mass of a few stars. The super-massive class can weigh millions or billions of stellar masses and reside at the centers of galaxies. Astronomers have debated for years whether a middleweight category exists, with evidence several times suggesting they do but then being refuted.

Now, astronomers have scoured one of the few suspected hiding spots for medium-sized black holes in a globular cluster, and conclude they are rare or nonexistent.

"Some theories say that small black holes in globular clusters should sink down to the center and form a medium-sized one, but our discovery suggests this isn't true," said Daniel Stern, an astrophysicist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and co-author of the study detailed in the Aug. 20 issue of Astrophysical Journal.

Scientists had thought that medium black holes might lie hidden, http://www.space.com/scienceastronomy/blackhole_trick_030120.html , among millions of stars in globular clusters, which sit within galaxies containing hundreds of billions of stars. Such black holes ranging in size from 1,000 to 10,000 times the mass of the sun should sit inside globular clusters like scaled-down versions of galactic black holes — at least in theory.

Previous studies have hinted at the existence, http://www.space.com/scienceastronomy/080402-medium-black-holes.html , of medium black holes, fingering star clusters with suspiciously large masses.

To see if there was anything to this, Stern worked with researchers led by Stephen Zepf, an astronomer at Michigan State University in East Lansing, to probe a globular cluster located 50 million light-years away in a neighboring galaxy. (A light-year is the distance light will travel in a year, or about 6 trillion miles or 10 trillion kilometers.)

They eventually found the X-ray signature of an active black hole in the globular cluster named RZ2109, using the European Space Agency's XMM-Newton telescope.

Next, the researchers determined the size of the black hole by using the W.M. Keck Observatory on Mauna Kea in Hawaii to get the chemical fingerprint of the globular cluster. Computer simulations of the chemical analysis revealed high-speed "winds" coming out of the black hole, indicating that it was baby consuming too much material and spitting some of it out.

"If an intermediate-sized black hole were accreting this material, it wouldn't be too big of a deal for it," Zepf said. "But if a small black hole were accreting this material, it would be a lot for it to take and therefore some material would be ejected in the form of high winds."

The astronomers estimated that the black hole was relatively tiny at just 10 times the mass of our sun.

"If a medium black hole existed in a cluster, it would either swallow little black holes or kick them out of the cluster," Stern explained.

Zepf suggested that medium-sized black holes might still lie hidden in dwarf galaxies on the outskirts of larger galaxies such as our Milky Way, but it would be difficult to track down.

A Video: http://www.space.com/common/media/video.php?videoRef=black_holes

Original Publication: http://www.livescience.com/space/080820-black-hole-sizes.html

posted in Astronomy & Astrophysics - 1 reply

New Evidence on Dark Energy/Matter (Related Discussion)

2008-08-05T13:35:15Z

http://cosmologytalk.tribe.net/thread/218ace7c-3244-4458-a57d-136e7653e69c

posted in Astronomy & Astrophysics - 4 replies

Fresh puzzle over dark energy supernovae

2008-07-07T16:23:28Z

05 July 2008
From New Scientist Print Edition.

IT'S an embarrassing gap in astronomers' knowledge. Despite relying on type Ia supernovae as tools to measure the dark energy speeding up the universe's expansion, they still don't know exactly what causes the blasts. Now, the picture has got even fuzzier.

In the standard scenario, a white dwarf pulls matter from a companion star, and this extra mass triggers a supernova. Heavy white dwarfs were thought more likely to explode, since it takes less to push them over the edge.

Now, Christopher Pritchet of the University of Victoria in British Columbia, Canada, and colleagues have observed galaxies dominated by lightweight white dwarfs producing type Ia supernovae just as efficiently as those dominated by heavier white dwarfs. These cases may be down to the collision of two white dwarfs, says co-author Andrew Howell of the University of Toronto.

The study will appear in The Astrophysical Journal Letters...

From: http://space.newscientist.com/channel/astronomy/cosmology/mg19926635.000-fresh-puzzle-over-dark-energy-supernovae.html?feedId=cosmology_rss20

posted in Astronomy & Astrophysics - 4 replies

Gamma-Ray Hunter Powers Up

2008-07-05T15:45:37Z

By Space.com Staff

posted: 02 July 2008
04:03 pm ET

NASA's GLAST space observatory has powered up and started sending signals back to Earth.

The Gamma-Ray Large Area Space Telescope launched on June , http://www.space.com/missionlaunches/080611-glast-launch.html ,1 and entered an orbit 345 miles (555 km) above Earth. Now one of its two instruments, the Large Area Telescope (LAT), has been awakened to begin streaming data to the Stanford Linear Accelerator Center's (SLAC) operations center.

"Powering up the LAT has been even smoother than we had hoped," said Rob Cameron, operations manager at SLAC. "We're already receiving high-quality data that we can use to get the instrument ready for the best science return."

GLAST will use gamma-ray vision, http://www.space.com/scienceastronomy/080310-mm-grb-us.html , to see the most energetic light in the universe and investigate extreme environments, http://www.space.com/scienceastronomy/080603-st-glast-telescope.html , such as black holes and pulsars. The space telescope will also examine the origin of powerful cosmic rays and possibly answer questions about dark matter.

The GLAST instruments are slated to undergo a 60-day checkout and calibration period before officially starting the first year of its mission, when it will do a full-sky survey and quickly respond to any detected sources of gamma-ray bursts.

"We're off to a great start and we're looking forward to a new view of our universe once science operations begin," said Peter Michelson, a principal scientist for LAT at Stanford University in California.

Video: GLAST Rockets into Space - http://www.space.com/php/video/player.php?video_id=080611-glast-launch

Original Publication: http://www.space.com/missionlaunches/080702-glast-powers-up.html

posted in Astronomy & Astrophysics - 3 replies

TIME is different all over

2008-06-10T14:33:25Z

the sun burns slower than fire here
the center of the earth is in a different time scale than where we live
so when you hear ideas about 13.6billion, 12trillion, 20,000 years etc in regards to the universe as a whole, well then that person doesn't know what they are talking about
TIME IS DIFFERENT ALL OVER

posted in Astronomy & Astrophysics - 6 replies

MATH IS DONE

2008-06-08T05:42:21Z

there's the way space must be
the way we see it
and the way we draw it

we draw it on paper (2D cross section of what must be possible)
there are four sacred shaped that tesselate/repeat on paper:
equilateral triangle, square, hexagon, and circle
triangle = 1/6 of hexagon and hexagon is similar to circle

the "crossings" of these shapes begets the only possible structures of the "atom" - fundamental unit
triangle X triangle = tetrahedron
circle X circle = sphere
etc

notice that square X square = cube and a certain rotation of the cube = hexagon

ALL IS ONE motherfuckas

there's more...

posted in Astronomy & Astrophysics - 24 replies

Two of the Milky Way's Spiral Arms Go Missing

2008-06-05T00:12:49Z

Whitney Clavin 818-354-4673/818-648-9734
Jet Propulsion Laboratory, Pasadena , Calif.
whitney.clavin@jpl.nasa.gov

NEWS RELEASE: 2008-094
June 3, 2008

St. Louis , Mo. -- For decades, astronomers have been blind to what our galaxy, the Milky Way, really looks like. After all, we sit in the midst of it and can't step outside for a bird's eye view.

Now, new images from NASA's Spitzer Space Telescope are shedding light on the true structure of the Milky Way, revealing that it has just two major arms of stars instead of the four it was previously thought to possess.

"Spitzer has provided us with a starting point for rethinking the structure of the Milky Way," said Robert Benjamin of the University of Wisconsin, Whitewater, who presented the new results at a press conference today at the 212th meeting of the American Astronomical Society in St. Louis, Mo. "We will keep revising our picture in the same way that early explorers sailing around the globe had to keep revising their maps."

An artist's concept of the structure of our two-armed Milky Way is online at http://www.nasa.gov/mission_pages/spitzer/multimedia/20080603a.html .

Since the 1950s, astronomers have produced maps of the Milky Way. The early models were based on radio observations of gas in the galaxy, and suggested a spiral structure with four major star-forming arms, called Norma, Scutum-Centaurus, Sagittarius and Perseus. In addition to arms, there are bands of gas and dust in the central part of the galaxy. Our sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms.

"For years, people created maps of the whole galaxy based on studying just one section of it, or using only one method," said Benjamin. "Unfortunately, when the models from various groups were compared, they didn't always agree. It's a bit like studying an elephant blind-folded."

Large infrared sky surveys in the 1990s led to some major revisions of these models, including the discovery of a large bar of stars in the middle of the Milky Way. Infrared light can penetrate through dust, so telescopes designed to pick up infrared light get better views of our dusty and crowded galactic center. In 2005, Benjamin and his colleagues used Spitzer's infrared detectors to obtain detailed information about our galaxy's bar, and found that it extends farther out from the center of the galaxy than previously thought.

The team of scientists now has new infrared imagery from Spitzer of an expansive swath of the Milky Way, stretching 130 degrees across the sky and one degree above and below the galaxy's mid-plane. This extensive mosaic combines 800,000 snapshots and includes over 110 million stars.

Benjamin developed software that counts the stars, measuring stellar densities. When he and his teammates counted stars in the direction of the Scutum-Centaurus Arm, they noticed an increase in their numbers, as would be expected for a spiral arm. But, when they looked in the direction where they expected to see the Sagittarius and Norma arms, there was no jump in the number of stars. The fourth arm, Perseus, wraps around the outer portion of our galaxy and cannot be seen in the new Spitzer images.

The findings make the case that the Milky Way has two major spiral arms, a common structure for galaxies with bars. These major arms, the Scutum-Centaurus and Perseus arms, have the greatest densities of both young, bright stars, and older, so-called red-giant stars. The two minor arms, Sagittarius and Norma, are filled with gas and pockets of young stars. Benjamin said the two major arms seem to connect up nicely with the near and far ends of the galaxy's central bar.

"Now, we can fit the arms together with the bar, like pieces of a puzzle," said Benjamin, "and, we can map the structure, position and width of these arms for the first time." Previous infrared observations found hints of a two-armed Milky Way, but those results were unclear because the position and width of the arms were unknown.

Though galaxy arms appear to be intact features, stars are actually constantly moving in and out of them as they orbit the center of the Milky Way, like London commuters in a busy traffic circle. Our own sun might have once resided in a different arm. Since it was formed more than 4 billion years ago, it has traveled around the galaxy 16 times.

Co-investigators of this research include Ed Churchwell, Marilyn Meade and Brian Babler of the University of Wisconsin, Madison; Barbara Whitney of the Space Science Institute, Madison, Wis.; Rémy Indebetouw of the University of Virginia, Charlottesville; and Christer Watson of Manchester College, Ind. NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA's Science Mission Directorate, Washington. Science operations occur at the Spitzer Science Center at the California Institute of Technology, also in Pasadena . For more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer .

-end-

From: Subscription Email

posted in Astronomy & Astrophysics - 1 reply

Why don't they...

2008-05-30T20:33:56Z

Why don't they create a computer program that can simulate what other planets in other systems are like?

Start off with a star (any kind, with adjustable size and molecular contents)
The star goes nova (or 'dies') and the fun starts.
Ejected gas is strewen about in somewhat of a layered way (I assume)
The Acreation process starts
Planets form
Then, how many of these planets would have the right stuff for life? What are the stats on finding an earth-like planet after running hundreds of simulations?

It would be interesting to have such a program developed. I'd bet it would be big and require a supercomputer to run.

posted in Astronomy & Astrophysics - 5 replies

Half of 1/25th of the missing Universe is found

2008-05-28T13:53:37Z

From Bad Astronomy Newsletter:

Half of 1/25th of the missing Universe is found
We’ve known for a long time that most of the Universe is invisible. 72.1% of it is dark energy, about which we know very little. 23.3% of it is dark matter, which was only recently tagged for real and for sure; we still don’t know what particles make it up, but we’re on the verge of finding out.

Normal matter — us — makes up just 4.6% of the Universe’s energy and mass budget. But here we are! At least, here we mostly are: actually, we only see roughly half of the normal matter in the Universe. Stars, galaxies, and warm-to-middling gas aren’t too hard to spot in general, but they only make up about half of what we expect to see of normal matter.

Where’s the other half?

Let’s turn the wayback machine to about 13.6 billion years or so ago. The Big Bang is old news at this point, but the first stars have yet to be born. Matter and energy are mixed everywhere, but some of it is different. What we now call dark matter is starting to clump together through gravity, forming long sheets and filaments far bigger than any galaxy we see today. This forms a grid, a framework, upon which normal matter starts to fall. Eventually, galaxies and clusters of galaxies and clusters of clusters of galaxies will form along these cosmic skeletons.

Fast forward to today. Bang! We see galaxies everywhere… well, not exactly everywhere. We see them lying in those long sheets and filaments, showing us where the dark matter structures are, like dew drops on a spider’s web.

But that’s just the stars and galaxies, remember? It’s only half. Where’s the other normal matter?

The hypothesis is was that it would be in the form of very hot gas strung out along those filaments as well. Hunting for it would be hard: it would be very diffuse, making it dim, and very hot, meaning it would only emit at short wavelengths, like extreme ultraviolet or X-rays.

Hey, we have telescopes that can see those!

And now we have. Astronomers upped the odds of finding the gas by looking around galaxy clusters, where it would be denser, and also doing something clever: looking near clusters that are near each other in the sky due to perspective. One would actually be farther away than the other, but peering very nearly along the angle separating them they would look like they’re right next to each other. Since we’d be looking along a long thin cylinder of gas, that would make it appear brighter than if we saw it through its side.

The picture above shows the galaxy clusters Abell 222 and 223, both about 2.5 billion light years away. The visible light image just shows them as clumps of points, but remember: each dot is a massive galaxy like our own! The technicolor bit is from the XMM-Newton orbiting X-ray observatory, and shows the hot gas. Since these are separate clusters, they should be detached from each other. But instead, they’re connected by a gas bridge of ten-million-degree plasma. That’s the missing stuff! That’s made up of baryons; particles like protons and neutrons, atomic nuclei and the like. Look around you: everything you see is made of baryons (and leptons, which include electrons), so this gas is your kin.

It’s a bit more rarified, though: there are only about 30 baryons per cubic meter in this bridge. Good thing it’s big (about 4 million light years wide) and we’re looking down its length! But then, that’s why so much of this stuff is missing. It’s really hard to detect.

According to the models, there is enough stuff in this bridge to extrapolate the existence of the rest of the missing normal matter. Of course, we only have a data set of one, which is a bit rocky, but I suspect more of these will be found now that we know they’re out there.

And may I add, phew! It’s always nice when half the stuff you can’t find finally turns up.

posted in Astronomy & Astrophysics - 10 replies

Quasar Red Shift Periodicity

2008-05-06T23:24:07Z

Apeiron, No. 7, Summer 1990 28
© 1990 C. Roy Keys Inc. – http://redshift.vif.com
(Halton Arp, APEIRON 5, 7)

Quantum causality on an extragalactic scale seems to me prematurely concluded where it is based upon the non-velocity interpretation of quasar red shifts. Arp makes a strong case in Quasars, Red shifts and controversies that quasars are blobs of matter ejected from active galaxies. Taking this hypothesis further leads me to the following conclusions.
To eject quasars, the central galactic machinery must have a mass much larger than quasars. I don’t subscribe to black hole theory, and prefer to call this galactic machine the ‘nucleus’. The nucleus must have reached a critical combination of mass and rotation to split up.
We should find out the energy needed for ejection and ask whether it can be furnished by the energy of rotation of the nucleus. Quasar ejection re-establishes nucleus stability until matter accretion brings it to the next ejection. The nucleus should be alternating between an advanced Jacobi ellipsoidal shape and the Poincaré instability at which splitting is a must. The nucleus rotation speed of active galaxies should be all close to a typical value because of the similar galactic characteristics. The accretion rate of the nucleus is determined by the galactic spirals. The mass-flow velocity in the spirals determines the time period between two quasar ejections. The average ejection period must be typical because of the expected statistical equalities of mass, rotation and accretion rates of all nuclei of active galaxies. The red shift difference between subsequently ejected quasars is determined by the quasar red shift deterioration rate (–z) per unit time and the ejection period T, where z/T = 72 km/sec, with z being the red shift reduction between ejections.
Because quasars are ejected from the strong gravity field of the galactic nucleus, they must have particle conditions with considerably lowered rest mass values. The lowered rest mass of freshly ejected quasars corresponds with the nucleus and not with the gravity field of the quasar. Elsewhere (cf. J.P. Nieland, Optical Aether Theory of Cosmology and Physics), I explain that rest mass reduction is significantly more than gravity theory alone predicts. The abnormally low rest mass makes quasars efficient machines to turn accreted matter into an abundance of light. The lowered rest mass of surface atoms prevents the build-up of an atmosphere, as with stars. Accretion should result in two types of emission, one during accretionary approach and the other immediately after impact. On impact the excess kinetic energy will be shed and contact with surface atoms of abnormal rest mass will produce additional radiation. Internal radiant energy production through baryon annihilation cannot be considered because it would make quasars self-sufficient in re-normalizing the abnormal rest mass. The quasar’s rest mass deficiency can be replenished only by incident radiation.
Quasar red shift cannot be related to luminosity in the normal stellar manner. Since very young quasars have not had the time to bring the accretion into full swing, they will have the lowest luminance and the highest red shift. Quasar luminance should grow with time depending on the opportunity for matter accretion. Quasar ejection into a thin galactic halo causes quasar luminance to grow slowly and preserves the high red shift longer. This may be responsible for some of the deviations in Halton Arp’s quasar statistics.
My quasar hypothesis is based only on the evidence in Arp’s Quasars, Red shifts and Controversies. Other support may exist but it is beyond my reach. Another weak point in the above arguments is the accretion rate of the central nucleus, which depends on the hypothesis of galactic spirals flowing inwards. I have no in-depth knowledge to spiral theories, but can offer my own.
Matter in the galactic disk is subjected to the pull of gravity and outward radiant pressure. Galactic emission of particles as cosmic rays demands an equal inflow of matter in the average galaxy. The galactic disk picks up the returning matter, including gas clouds which have been pushed away by radiant pressure at an angle to the disk. The spiral flow towards the galactic nucleus must equal the outward flow of cosmic rays and gas clouds.
Active stars like the sun have about 10 billion times the surface area of dead stars, they therefore move minutely slower due to gravitation along the spiral arms. The gravity in the spirals keeps all stars close together in a string. In the spiral direction, different velocities must be expected for dead and living stars, the latter being minutely slowed down by radiation pressure. These flow differences should cause dead stars to congregate in the front of the spiral and live stars in the rear. A radiant temperature gradient should be observed across the spiral width.
Halton Arp’s non-velocity quasar red shift therefore implies that quasars are ejected regularly at a time rate which is hidden in the quasar red shift periodicity of 72 km/sec. This periodicity cannot be interpreted as quantum causality.

Joop F. Nieland
Rue Barri d’Avall à Corsavy
66150 Arles sur Tech
France

"Demystification of Science"

Science encounters a wealth of new observations about nature almost daily. Many of these observations translate into remarkable technology. Science glamorizes its role to the world, yet in conveying many important observations to others it is often very ineffective.
Communication within experimental projects of science is generally a cooperative venture, with a number of scientific disciplines moving toward a common objective. Mathematics and shorthand symbols define the physical quantities that are needed to work out the best solution to a problem. That kind of scientific communication, however, builds on a logic that mirrors the realities of nature.
The primary concern of a theoretical physicist and other science theorists is different from that of experimental scientists. Facts are interesting to the theorist because of the possibility of a common connection with one another and because of the suggestion they give of what might actually be happening in nature. It is logic which ties those facts together and fascinates the theorist. That logic builds a concept that can be adapted to many different situations. While many logical concepts about nature are capable of mathematical usage and translation into very familiar scientific symbols, that use is secondary to the value of the logical concept itself.
The mathematics of how many angels can stand on the head of a pin can appear to be quite profound to a mathematician, but is entirely lacking in physics. When we read "Descartes’ Dream" by Philip J. Davis and Reuben Hersh, we come to realize that describing things mathematically does not always bring precision. By looking into the logic rather than the mathematics, we can open many more opportunities to the understanding of reality. Whoever chooses to translate the logic into mathematics can make the attempt, but other applications are available as well.
Thousands of scientific papers are offered every year in pursuit of academic ambition. Most of the insights they may contain are lost in the jargon of science, and they require detailed evaluation if a professional evaluation is to be the result. The rest of us who are jargon illiterate are completely unable to benefit from the concepts.
The style of Stephen Hawking in his A Brief History of Time is greatly to be preferred to the scientific equivalent of speaking in tongues. Hawking proved in his book to a very wide audience that it was not necessary to utilize mathematics in order to describe important statements of modern science. It would not even matter that a few of those statements might be mistaken. There is special value in widening contemplation over whether the logic is sound or not. Old theories can be mistaken theories, and adding to the number of minds dwelling on the problem only adds the likelihood of better logic.
Experimental scientists who are able to write in popular language give the details of their experiments. They simply translate those details in broader fashion and more understandably - when that happens, science benefits. Others may see what never even occurred to the experimentalist. Demystification of science is important to bring men and women to science, and science to men and women. The real mark of professionalism lies in not only understanding what one is about, but in being able to explain and justify its logic. That means more than just giving mathematics and symbols. There are a number of journals which attempt to make the transition from the mathematics and symbols of the profession to the fundamental concept. One of the most notable is Technology Review, published by the Massachusetts Institute of Technology.
Experimenters present agreeable translations of the symbols and mathematics employed in the work itself. They do not stint on detail, but they present the detail in a manner that is more meaningful. Writing discipline of that kind rewards the experimenter as well as the reader. Whether the reader is a scientist or a mere seeker after scientific knowledge, no one suffers from making reality available through the artistry of popular language.
Other journals, of course, such as Scientific American, Physics Today, Nature, and so forth, provide us with a certain amount of vernacular explanation, but too many of those writers lapse into incoherence very quickly with their dependence on science jargon. There is a time and place for mathematics, but the place is not in journals, unless it is a journal devoted to mathematics, and the time has long since passed when scientific concepts need to be limited to experimental subjects.
Philip W. Anderson, the Joseph Henry Professor of Physics at Princeton University, wrote in the February 1990 issue of Physics Today, “Even in theoretical physics, most of the great advances have been conceptual rather than mathematical. The basic goal of physics is not mathematical elegance or even the achievement of tenure, but learning the truth about the world about us.”
If scientists grab for the brass ring of conformity rather than looking to present new understanding of basic logic, substance will never triumph over form.

Merle Bergmann
446 N. Sweetzer Avenue
Los Angeles, California 90048

_____________________________________________

Original (from): http://redshift.vif.com/JournalFiles/Pre2001/V0N07PDF/V0N07ISS.pdf

posted in Astronomy & Astrophysics - 8 replies

New Mathematics reshaping physics

2008-03-30T19:40:31Z

check out www.i-b-r.org Math models of points, lines and planes are responsible for glaring inaccuracies that quantum physics manifests. As far as I can tell, quarks and strings are like imaginary numbers - what must be invented to fill in the gaps. Please review the work and post any discrepancies, but I think you'll find the new einstein

posted in Astronomy & Astrophysics - 0 replies

Flipping particle could explain missing antimatter

2008-03-28T14:13:16Z

18 March 2008
From New Scientist Print Edition.
Valerie Jamieson

It is one the biggest mysteries in physics - where did all the antimatter go? Now a team of physicists claims to have found the first ever hint of an answer in experimental data. The findings could signal a major crack in the standard model, the theoretical edifice that describes nature's fundamental particles and forces.

In its early days, the cosmos was a cauldron of radiation and equal amounts of matter and antimatter. As it cooled, all the antimatter annihilated in collisions with matter - but for some reason the proportions ended up lopsided, leaving some of the matter intact.

Physicists think the explanation for this lies with the weak nuclear force, which differs from the other fundamental forces in that it does not act equally on matter and antimatter. This asymmetry, called CP violation, could have allowed the matter to survive to form the elements, stars and galaxies we see today.

The standard model, our best effort to describe the universe's structure, fails to fully explain CP violation. Many alternative theories claim to have the answer, such as those incorporating supersymmetry, extra dimensions and hitherto unseen forces. However, they often invoke new particles, and experiments have yet to turn up evidence of these.

Particle physicists have long thought that they might find such evidence in a particle called the Bs meson, which comprises a bottom antiquark bound to a strange quark. The Bs is one of a handful of mesons that transforms into its own antiparticle and back again 3 trillion times per second before decaying into other particles (see Diagram). These oscillations between matter and antimatter make it a good place to look for evidence that CP violation goes beyond the standard model.

At the Tevatron particle accelerator at Fermilab in Batavia, Illinois, two groups of scientists running the rival CDF and D-Zero experiments have been studying several properties of Bs mesons and their oscillations by picking through the debris created when protons and antiprotons collide. While each experiment on its own has found faint hints of CP violation above and beyond the standard model, the experimental uncertainties have been too large to make a definitive claim, says Giovanni Punzi, a physicist at the University of Pisa in Italy and one of the leaders of the B meson physics group at CDF.

Now Luca Silvestrini at Italy's National Institute of Nuclear Physics (INFN) in Rome and colleagues in Italy, France and Switzerland have managed to reduce these uncertainties. By combining the published results of the CDF and D-Zero teams, they have shown there seems to be much more CP violation than the standard model permits. "We can say with greater than 99.7 per cent probability that CP violation is there," says Silvestrini ( http://arxiv.org/abs/0803.0659 ). In other words, new physics is at work in the oscillations. His group cannot yet say what kind of new physics - that will require others to test whether existing theories explain the data.

"It is tantalizingly interesting at the moment," says Val Gibson, an expert on B meson physics at the University of Cambridge. "If it is true, it is earth-shattering."

Jacobo Konigsberg, who leads the CDF collaboration, says that Tevatron researchers are "cautiously excited" about the analysis. He points out that more data needs to be analyzed to rule out a statistical fluke, which has happened several times before in particle physics.

The real proof could come later this year when the Large Hadron Collider switches on at CERN, near Geneva, Switzerland. The LHC-b experiment has been designed specifically to study mesons containing bottom quarks. "LHC-b will make an unambiguous measurement within two months," says Gibson.

Original Publication: http://space.newscientist.com/channel/astronomy/mg19726483.600-flipping-particle-could-explain-missing-antimatter.html

posted in Astronomy & Astrophysics - 10 replies

Universe submerged in a sea of chilled neutrinos

2008-03-26T17:50:12Z

22:00 05 March 2008
NewScientist.com news service
Stephen Battersby

We are all submerged in a sea of almost undetectable particles left over from the first few seconds of the big bang, according to the latest observations from a NASA satellite. The Wilkinson Microwave Anisotropy Probe (WMAP) has confirmed the theory that the universe is filled with a fluid of cold neutrinos, http://www.newscientist.com/channel/fundamentals/mg19526151.700-neutrinos-the-key-to-a-theory-of-everything.html , that remain almost entirely aloof from ordinary matter.

Cosmologists think that in the hot, dense, young universe, neutrinos should have been created in high-energy particle collisions. About two seconds after the big bang, the cauldron of colliding particles would have cooled down so much that most would not have had enough energy to interact strongly with neutrinos. The neutrinos would then have "de-coupled" from other matter and radiation.

In theory, they should still be buzzing around, a soup of slippery particles that by today has been chilled to a temperature of only 1.9 ° Celsius above absolute zero.

Now WMAP has found evidence of this cosmic gazpacho. The spacecraft, launched in 2001, has been building up a picture of the cosmic microwave background radiation, which carries a detailed imprint of the state of the universe 380,000 years after the big bang. In particular, it reveals the pattern of density fluctuations in space, the "texture" of the early universe.

Travelling at nearly the speed of light, neutrinos should have discouraged matter from forming tight clumps, and so smoothed out the texture of the universe slightly.
Only detector

The WMAP data clearly show this smoothing effect, implying that those fast-flowing neutrinos formed about 10% of all the energy in the 380,000-year-old universe. "This confirms the theory," says Eiichiro Komatsu of the University of Texas in Austin, US, lead author of a study about the result.

In 2005, another analysis, http://space.newscientist.com/article/dn7533-big-bang-neutrinos-smoothed-out-the-universe.html , also provided evidence for a cosmic neutrino background, but it relied on combining WMAP data from other sources, and making some assumptions about other cosmological parameters, says Komatsu. Now that WMAP has collected five years' worth of data, it is enough to show firm evidence of the neutrino background on its own.

The neutrinos are too weak to be detected individually. "These neutrinos cannot be detected on the ground; you need the CMB to do it," Komatsu told New Scientist.

Other neutrinos, for example those generated in the Sun's core, can be detected on Earth, often in large tanks of water buried deep underground, where an occasional neutrino is unlucky enough to hit an atomic nucleus. But cosmic background neutrinos have only a millionth of the energy of a typical solar neutrino, making them even more ethereal.

To stop a substantial fraction of solar neutrinos, you would already need a lead shield a light year thick, says Komatsu. How about cosmic background neutrinos? "I'd estimate you would need a block of lead that is thicker than the entire universe."

Original Publication: http://space.newscientist.com/channel/astronomy/dn13414-universe-submerged-in-a-sea-of-chilled-neutrinos.html

posted in Astronomy & Astrophysics - 3 replies

telescope problems

2008-03-08T14:16:22Z

my friends sent me this email. perhaps you guys know the answer.
just traded for another telelscope--my problem--this scope has been sitting forever.
I started disassembling it to clean it up, and ran across a REAL problem and hope someone has an idea to correct it.
The reflector mirror has calcium deposits on it, without this mirror, I own an expensive hollow tube on an expensive telescope mount.
Does anyone have an idea to safely, carefully. remove calcium deposits from a precision mirror?

posted in Astronomy & Astrophysics - 19 replies

Has 'dark fluid' saved Earth from oblivion?

2008-03-06T16:33:22Z

06 March 2008
Zeeya Merali
Magazine issue 2646

FRESH battle lines are being drawn in the debate over whether dark matter is needed to explain the structure of galaxies.

Those physicists who would like to throw out dark matter in favor of a controversial new form of gravity are facing one of their biggest challenges yet. It seems that if their theory is valid, the Earth should have been swallowed up long ago by black holes that would regularly appear in our solar system. Dark matter's opponents are not ready to give up just yet, though. A "dark fluid" sloshing around galaxies like ours might just allow them to fight another day.

Dark matter has been proposed to explain why spiral galaxies are not torn apart by their rapid rotation. The favored view among cosmologists is that the gravitational force exerted by some kind of dark matter must be pulling the outer stars in. Though physicists are closing ...

more: http://space.newscientist.com/article/mg19726464.200-has-dark-fluid-saved-earth-from-oblivion.html?feedId=space_rss20

posted in Astronomy & Astrophysics - 0 replies

Violent Collision of Stellar Winds Detected

2008-03-04T18:26:45Z

By Andrea Thompson
Staff Writer
posted: 03 March 2008
05:47 am ET

For the first time, astronomers have pinpointed the spot where the intense winds of two massive stars in a binary system violently collide and detected the production of high-energy X-rays there.

The monstrously large Eta Carinae, http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=080229-carina-nebula-02.jpg&cap=An+image+of+the+Carina+Nebula+as+seen+by+the+Hubble+space+telescope.+The+location+of+Eta+Carinae+is+indicated.+Credit%3A+NASA%2C+ESA%2C+UCB+%28N.+Smith%29%2C+STScI%2FAURA+%28The+Hubble+Heritage+Team%29 , binary contains between 100 and 150 times the mass of the sun and glows more brightly than four million suns together. The so-called hyper-giant contains two massive stars, the second of which was not discovered, http://www.space.com/scienceastronomy/051101_eta_car.html , until 2005.

Astronomers have long suspected that the stellar pair should give off high-energy X-rays, but until now, they didn't have the instruments to detect the radiation. But the European Space Agency's Integral telescope, http://www.space.com/scienceastronomy/integral_telescope_021014.html , launched to detect some of the most violent events in the universe, has conclusively detected such X-rays emanating from Eta Carinae, more or less as astronomers had thought.

"The intensity of the X-rays is a little lower than we expected, but given that this is the first-ever conclusive observation, that's OK," said Jean-Christophe Leyder of the University of Liege in Belgium, one of the astronomers who made the discovery.

Stellar wind shock wave

The intense X-rays are generated by the collision of the massive stars' stellar winds, flows of charged gas ejected from the stars' upper atmospheres.

The light and other radiation that "blows" off these particles is so strong that the stellar winds of Eta Carinae, http://www.space.com/scienceastronomy/eta_car_031202.html , can reach speeds of 900 to 1200 miles per second (1,500 to 2,000 kilometers per second). Because the two stars are in such close proximity, the winds collide in a ferocious shock wave where temperatures reach several thousand million degrees Kelvin. "It's a very tough environment," Leyder said.

Electrons get caught in the magnetic environment of the shock waves and are bounced back and forth, accelerating to huge energies. When they finally burst out of the shock wave, they collide with low-frequency photons and give them an energy boost, creating the high-energy X-ray emissions spied by Integral.

Search for other emitters

Finding other examples of colliding-wind binaries, as astronomers call them, is tough because massive stars are rare; finding two in a binary system is rarer still.

"In our galaxy, there are probably only 30 to 50 colliding-wind binaries that display a clear signature of wind-wind collision," Leyder said. This meager number of stars is just a tiny fraction of the galaxy's stellar population. So to have an example such as Eta Carinae on our cosmic doorstep is a stroke of luck.

Astronomers did detect X-rays emitted from another colliding-wind binary, HD 5980, in our galactic neighbor the Small Magellanic Cloud,http://www.space.com/scienceastronomy/astronomy/chandra_image_000414.html , last year.

The X-rays detected from Eta Carinae are of a much higher energy though. Astronomers estimate that the Eta Carinae system loses one Earth mass per day of ejected material, roughly 140 times higher than the mass loss rate of HD 5980.

Understanding the X-ray emissions from stellar winds is important because stellar winds affect the evolution of stars and the chemical evolution of the universe, while also acting as a source of energy in the galaxy.

Original Publication: http://www.space.com/scienceastronomy/080303-mm-stellar-wind-collision.html

posted in Astronomy & Astrophysics - 2 replies

Could meteorite discovery weaken dark energy's case?

2008-03-03T15:27:42Z

19:00 28 February 2008
NewScientist.com news service
Stephen Battersby

Whiskers of carbon found in ancient meteorites could hold clues to the earliest days of the solar system. More controversially, they might cast a shadow over the concept of dark energy, http://www.newscientist.com/article/mg19325911.700-dark-energy-seeking-the-heart-of-darkness.html , the unknown force that seems to be accelerating the expansion of the universe.

Graphite whiskers are rolled-up sheets of carbon atoms that are so tightly furled they measure just 1 micron or so thick. The needle-like structures have been created under high-temperature conditions in the lab but have never previously been detected in space. Still, astronomers had postulated that they form in the heat of supernova explosions and around young stars.

Now, Marc Fries and Andrew Steele of the Carnegie Institution of Washington in the US, have found what they think are graphite whiskers in three so-called carbonaceous chondrite meteorites, which contain some of the oldest material in the solar system.

They studied dark patches in the meteorites using a technique called Raman spectroscopy, which shines a laser on a material to make it emit infrared light. The distinctive infrared spectral fingerprint produced is a signature of the molecular structure of a graphite whisker, which resembles a tiny, rolled-up poster, says Fries.

In the meteorites, the whiskers occur in and around mineral fragments called calcium-aluminium-rich inclusions, http://en.wikipedia.org/wiki/Ca-Al-rich_inclusion . CAIs, as they are called, are thought to have been among the first solid objects in the solar system, condensing about 4.5 billion years ago, so the whiskers were probably forged around the same time.

Scientists still don't know what was going on in the solar system at the time, or what produced the high temperatures necessary to create these materials. "It's a portion of the history of our solar system we don't have a really good handle on," Fries told New Scientist.

Distinctive spectrum

That is where whiskers could help. Because they have such a distinctive spectrum, astronomers might be able to detect them around young stars in our galaxy, which would then give us a picture of what our solar system looked like at the time. That could give scientists some clues about how the first rocky fragments formed around the Sun, and how they eventually grew into planets.

Fries and Steele also suggest that these whiskers might have been pumped out into deep space by the solar wind, and that the combined whisker output of many young stars might have filled interstellar space with whiskers.

If so, they might have some relevance to dark energy. The unexpected dimness of distant supernova explosions at certain infrared wavelengths was what first led astronomers to the conclusion that the expansion of the universe is accelerating, and the proposal that some form of mysterious "dark energy" is to blame.

Some astronomers, however, suggested that the size and special geometry of graphite whiskers might be the cause of this dimness, absorbing light from distant supernovae at the key infrared wavelengths (between 3 and 9 microns). Now that Fries and Steele have shown that these whiskers are indeed created in space, could they pose problems for the dark energy hypothesis?

'Immense extrapolation'

Not according to Adam Riess of the Space Telescope Science Institute in Baltimore, Maryland, US. "This is an immense extrapolation," says Riess, one of the co-discoverers of the accelerated expansion. "Seeing a few whiskers in a meteor means they fill interstellar space blocking 25% of all the light we see? That's quite a stretch."

He adds that the dimming goes away as astronomers look back to the most ancient supernovae. That fits the dark energy picture because in those early days it had much less effect on the universe. If dimming is caused by whiskers, it's harder to explain. "Where did the whiskers go?" says Riess.

Finally, he points out that there are now several independent lines of evidence that point to dark energy, all agreeing with the supernova data.

"There are other indicators of dark energy, no doubt about that," admits Steele. "But the supernova observations were the first. Now we've seen whiskers, there's no harm in looking to see if they have an effect [on dark energy]."

Journal reference: Sciencexpress (DOI:10.1126/science.1153578), http://www.sciencemag.org/sciencexpress/recent.dtl .

Original Publication (w/ pic.): http://space.newscientist.com/article/dn13392-could-meteorite-discovery-weaken-dark-energys-case.html?feedId=space_rss20

posted in Astronomy & Astrophysics - 1 reply

Is cosmic string the radio burst culprit?

2008-02-28T21:58:01Z

28 February 2008
Marcus Chown
Magazine issue 2645

LIKE a shout in the dark, a mysterious burst of radio waves from the depths of space has puzzled astronomers since it was discovered last year. Now one physicist is suggesting it came from the cosmic equivalent of a cracking whip.

In 2001, a radio burst lasting about 1 millisecond was picked up by the 64-meter Parkes radio dish in Australia. The signal went unnoticed at first, but last year a team led by Duncan Lorimer of West Virginia University, Morgantown, spotted it during a recap of archived observations.

By analyzing the time delays of different frequencies within the burst, they found it had traveled a huge distance - about 3 billion light years. The presence of a supernova, gamma-ray burster or galaxy would have explained its origin, but curiously none lies in that part of the sky. Though it is possible a stellar object such as a pulsar was ....

more: http://space.newscientist.com/article/mg19726454.100-is-cosmic-string-the-radio-burst-culprit.html?feedId=space_rss20

posted in Astronomy & Astrophysics - 0 replies

Dark Matter Stars...

2008-02-23T20:50:54Z

From the BBC:

http://news.bbc.co.uk/2/hi/science/nature/7252428.stm

posted in Astronomy & Astrophysics - 3 replies

Supercomputer Will Help Scientists Listen For Black Holes

2008-02-14T22:40:00Z

ScienceDaily

(Feb. 10, 2008) — Scientists hope that a new supercomputer being built by Syracuse University's Department of Physics may help them identify the sound of a celestial black hole. The supercomputer, dubbed SUGAR (SU Gravitational and Relativity Cluster), will soon receive massive amounts of data from the California Institute of Technology (Caltech) that was collected over a two-year period at the Laser Interferometer Gravitational-Wave Observatory (LIGO).

Duncan Brown, assistant professor of physics and member of SU's Gravitational Wave Group, is assembling SUGAR. The department's Gravitational Wave Group is also part of the LIGO Scientific Collaboration (LSC), a worldwide initiative to detect gravitational waves. Brown worked on the LIGO project at Caltech before coming to SU last August.

Gravitational waves are produced by violent events in the distant universe, such as the collision of black holes or explosions of supernovas. The waves radiate across the universe at the speed of light. While Albert Einstein predicted the existence of these waves in 1916 in his general theory of relativity, it has taken decades to develop the technology to detect them. Construction of the LIGO detectors in Hanford, Wash., and Livingston, La., was completed in 2005. Scientists recently concluded a two-year "science run" of the detectors and are now searching the data for these waves. LSC scientists will be analyzing this data while the sensitivity of the detectors is being improved. Detectors have also been built in France, Germany, Italy and Japan.

Before they can isolate the sound of a black hole from the LIGO data, the scientists must figure out what a black hole sounds like. That's where Einstein's theories come in. Working with colleagues from the Simulating eXtreme Spacetimes (SXS) project, Brown will use SUGAR and Einstein's equations to create models of gravitational wave patterns from the collision of two black holes. SXS is a collaborative project with Caltech and Cornell University.

Black holes are massive gravitational fields in the universe that result from the collapse of giant stars. Because black holes absorb light, they cannot be studied using telescopes or other instruments that rely on light waves. However, scientists believe they can learn more about black holes by listening for their gravitational waves.

"Looking for gravitational waves is like listening to the universe," Brown says. "Different kinds of events produce different wave patterns. We want to try to extract a wave pattern -- a special sound -- that matches our model from all of the noise in the LIGO data."

It takes massive amounts of computer power and data storage capacity to analyze the data against the gravitational wave models Duncan and his colleagues built. SUGAR is a collection of 80 computers, packing 320 CPUs of power and 640 Gigabytes of random access memory. SUGAR also has 96 terabytes of disk space on which to store the LIGO data.

It also takes a dedicated, high-speed fiber-optic network to transfer the data between Caltech and SU. To accomplish that, SU's Information Technology and Services (ITS) collaborated with NYSERNet to build a special pathway for the LIGO data on the high-speed fiber optic network that crisscrosses the United States. The one-gigabit pathway begins in the Physics Building and traverses SU's fiber-optic network to Machinery Hall and then to a network facility in downtown Syracuse, which the University shares with NYSERNet. From there, the pathway connects to NYSERNet's fiber-optic network and goes to New York City. In New York City, the pathway switches to the Internet2 high-speed network and traverses the country, ending in a computer room in Caltech.

Both the supercomputer and the high-speed network are expected to be up and running by the end of February. Once the data is transferred to SU from Caltech, Brown and his LSC colleagues will begin to listen to the "cosmic symphony." "Gravitational waves can teach us much about what is out there in the universe," Brown says. "We've never looked at Einstein's theory in this way."

LIGO is funded by the National Science Foundation and operated by Caltech and the Massachusetts Institute of Technology.

Adapted from materials provided by Syracuse University, http://www.syr.edu/ .

Original Publication: http://www.sciencedaily.com/releases/2008/02/080208131143.htm

posted in Astronomy & Astrophysics - 11 replies

"Periodic table" organizes zoo of black hole orbits

2008-02-13T23:31:26Z

16:55 13 February 2008
NewScientist.com news service
David Shiga

Physicists have found a hidden order to the zoo of strange paths that objects can trace in the curved space around black holes, allowing them to create a "periodic table" of black hole orbits.

The insights gained could help scientists focus their search for gravitational waves, ripples in space triggered by the motions of massive objects, such as a pair of orbiting black holes.

Far away from a black hole, an object will trace out an ellipse as it orbits the massive object, just like the planets in our solar system do as they orbit the Sun.

But very close to a black hole, Einstein's theory of general relativity predicts much weirder behaviour, due to the way the black holes' ultra-powerful gravitational fields warp the fabric of space. For example, an object might travel on an elongated path towards the black hole, then loop tightly around the hole one or more times before being flung outwards again on a stretched-out path.

Objects making such close passes follow paths that essentially never repeat in exactly the same way, their courses set by the objects' precise starting trajectories and speeds.

Discovering any hidden order in the bewildering variety of possible orbits might thus seem impossible, but physicists Janna Levin and Gabe Perez-Giz of Columbia University in New York City, US, have done just that.

They used mathematical models in which an object's starting trajectory and speed are tuned in just the right way to allow its orbit to eventually repeat itself exactly – a 'perfect' situation the authors say would never occur in the real world.

Cloverleaf pattern

An example of this is a cloverleaf pattern, where the object traces out each leaf in the pattern, then repeats the whole thing over again when it gets back to its starting point. "It's totally different from what we see in planetary orbit behavior," Levin told New Scientist.

The key, the researchers found, was that for every non-repeating path that real-world objects are likely to follow, there is a corresponding repeating one that traces a very similar course. For example, an object traveling on an elliptical orbit in which the orbit itself precesses, or rotates, around might be modeled by a flower-like structure with 10 million overlapping petals.

That discovery allowed the team to organize all of the possible paths into different groups, based on which repeating path they resemble – creating a periodic table for black hole orbits. "They sort themselves beautifully," Levin says.

This could be useful for scientists searching for gravitational waves, http://www.newscientist.com/article/mg15721258.700-gravity-waves.html , which are set in motion by the movement of massive bodies such as black holes.

Deciphering signals

That's because the actual pattern of gravitational waves produced by two orbiting black holes just before they merge, http://space.newscientist.com/article/dn9012-black-holes-collide-in-the-best-simulation-yet.html , depends on the shape of their orbits.

A better understanding of these orbits could give physicists a better idea of what to look for in data from gravitational wave observatories, which have a baffling array of possible signals to sift through in their searches of the entire sky.

And because pairs of orbiting black holes are described by 10 or so key numbers – including their mass, spin rate, and spin direction, the new periodic table could help physicists determine these physical characteristics from any gravitational waves they observe from such pairs, Levin says.

"I don't think anyone has tried to create such a classification before," says black hole expert Daniel Kennefick of the University of Arkansas in Fayetteville, US. "It very well could be a very fruitful idea," Kennefick told New Scientist. "But it's a funny thing about classifications – it's very difficult to tell until some time has passed how useful it's going to be."

Original Publication (w/ pics): http://space.newscientist.com/article/dn13316-periodic-table-organises-zoo-of-black-hole-orbits.html?feedId=space_rss20

posted in Astronomy & Astrophysics - 0 replies

dark matter query

2008-02-13T05:52:09Z

Clearly, at the time of the big bang, there was a localized disharge of a huge amount of energy,

from where it came, no one dares to say.

I have a question, because I dont have good data.

How many dark matter "basketballs" would have to be put into the equation to support driving the Universe

into the bound states of matter and energy in the Universe today?

I have studied the baryon density of the universe problem, with access to some great papers,

but I dont have the dark creation constant. Any clues?

posted in Astronomy & Astrophysics - 33 replies

Wormholes - The Door to a Parallel Universe

2008-02-09T22:11:42Z

Author: Amarendra Swarup

If there were a portal linking us to a parallel universe or some other region of space, how would we spot it? One suggestion is that it will give itself away by the curious way it bends light.

The existence of wormholes linking different regions of space was suggested in 1916 by the Austrian physicist Ludwig Flamm as a possible solution to equations of general relativity, which Einstein had published that year. They have since become accepted as a natural consequence of general relativity, which predicts that matter entering one end of a wormhole would instantly emerge somewhere else, so long as the wormhole is somehow propped open.

Though no direct evidence for wormholes has been observed, this could be because they are disguised as black holes. Now Alexander Shatskiy of the Lebedev Physical Institute in Moscow, Russia, is suggesting a possible way to tell the two kinds of object apart. His idea assumes the existence of a bizarre substance called “phantom matter”, which has been proposed to explain how wormholes might stay open. Phantom matter has negative energy and negative mass, so it creates a repulsive effect that prevents the wormhole closing.

According to Shatskiy’s calculations, the way phantom matter deflects light would give the wormhole a signature that astronomers could look out for. The gravity of an object with a positive mass, such as an ordinary black hole, focuses light rays passing close to it as if it were a giant concave lens – an effect known as gravitational lensing. Phantom matter’s negative mass would have the opposite gravitational lensing effect to normal matter, making any light passing through the wormhole from another universe or point in space-time diverge, and emerge from it as a bright ring. Meanwhile, any stars behind it would shine through the middle. Shatskiy suggests that his idea might offer a way for future space-based observatories such as Russia’s planned Millimetron Project to look for wormholes at the center of large galaxies.
...

more...
http://www.eurekalert.org/pub_releases/2008-01/ns-ftd013008.php

Original Publication: http://www.newscientist.com

The paper: http://arxiv.org/abs/0712.2572

posted in Astronomy & Astrophysics - 3 replies

Exploding black holes could expose hidden dimensions

2008-02-07T21:44:54Z

18:48 05 February 2008
NewScientist.com news service
Ker Than

Cosmic flares shot from exploding black holes could provide long-sought proof of extra spatial dimensions, new calculations suggest.

Theoretical physicist Stephen Hawking predicted that black holes evaporate through a quantum process known as "Hawking evaporation" and can explode in brief bursts of energy before vanishing completely.

Only mini-black holes roughly as massive as an asteroid or smaller would be able to evaporate completely within the lifetime of the universe. And such tiny black holes may have been created, http://space.newscientist.com/article/dn12665-did-the-big-bang-spawn-trillions-of-black-holes.html , in large numbers within 1 second of the big bang, as elementary particles clumped together at extreme energies.

Now, researchers led by Michael Kavic of Virginia Tech in Blacksburg, US, say the evaporation of such "primordial" black holes could emit detectable radiation – if the universe contains additional dimensions beyond the familiar three of space and one of time. Such extra dimensions are predicted in some theories that try to unify gravity and quantum mechanics, such as string theory, http://www.newscientist.com/channel/fundamentals/mg19726370.100-string-theory-may-predict-our-universe-after-all.html .

In the presence of extra dimensions, black holes would wrap around these extra dimensions to form "black strings", http://space.newscientist.com/article/dn9144-when-is-a-black-hole-like-a-dripping-faucet.html . "You can envision this as a rubber band wrapped around a fire hose," Kavic told New Scientist. "As the black hole evaporates, it eventually becomes too small to wrap the extra dimension."

Unique pulse

He and colleagues predict that when a black string snaps, it will expose the extra dimension by creating a pulse of radiation with a unique electromagnetic signature. "We would know them if we saw them," Kavic told New Scientist.

By analysing the frequency of the pulse, scientists could calculate the size of the extra dimension, which could lend insight into which cosmological model best describes the universe. "The size of the black string is directly related to the size of the extra dimension at the time of the explosion," Kavic says.

The team says the light pulses could be detected by radio telescopes capable of scanning the entire sky in one sweep, such as Virginia Tech's Eight-meter-wavelength Transient Array, http://www.ece.vt.edu/swe/eta/ .

"Traditional radio telescopes only focus on a very small part of the sky at any one time," Kavic said. "This means that they could easily have missed these kinds of pulses."

Good timing

The new test comes at an opportune time, says Charles Keeton, an astronomer at Rutgers University in New Jersey, US: "Our ability to observe exploding black holes is limited only by the sensitivity of our radio telescopes, and that is getting better."

But while much theoretical work has been done on primordial black holes and extra dimensions, their existence remains unproven.

"The big question is whether such black holes are produced in the first place," says Avi Loeb of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, US. "In principle, it's possible to make such black holes, but in the standard model of cosmology, it is not natural."

"There are a lot of layers here of nonstandard assumptions," Loeb told New Scientist. "If nothing could be observed in this context, then it would not surprise me."

While definitely a gamble, the payoffs from such a search would be enormous, Kavic argues. The successful detection of the kind of black hole explosion the team predicts would confirm not only the existence of extra dimensions, but also of primordial black holes and Hawking evaporation.

"All three of these are quantum gravitational phenomena [and] would drastically alter our view of space-time and the fundamental nature of our universe," Kavic says.

The team has submitted the study to Physical Review Letters, http://prl.aps.org/ .

Original Publication: http://space.newscientist.com/channel/astronomy/dn13279-exploding-black-holes-could-expose-hidden-dimensions.html?feedId=astronomy_rss20

posted in Astronomy & Astrophysics - 1 reply

Galaxy without dark matter puzzles astronomers

2008-02-06T16:43:47Z

06:59 06 February 2008
NewScientist.com news service
Stephen Battersby

What do you call an absence of darkness? Dark matter is supposed to be spread throughout the universe, but a new study reports a spiral galaxy that seems to be empty of the stuff, and astrophysicists cannot easily explain why.

In the outer regions of most galaxies, stars orbit around the centre so fast that they should fly away. The combined mass of all the observable inner stars and gas does not exert strong enough gravity to hold onto these speeding outliers, suggesting some mass is missing.

Most astronomers believe that the missing mass is made up of some exotic invisible substance, labeled dark matter, http://www.newscientist.com/channel/fundamentals/mg19125601.300-let-there-be-dark-matter.html , which forms vast spherical halos around each galaxy. Another possibility is that the force of gravity behaves in an unexpected way, a theory known as modified Newtonian dynamics, or MOND, http://space.newscientist.com/article/mg19526234.200-rival-theory-fights-back-against-dark-matter.html .

In the spiral galaxy NGC 4736, however, the rotation slows down as you move farther out from the crowded inner reaches of the galaxy. At first glance, that declining rotation curve is just what you would expect if there is no extended halo of dark matter, and no modification to gravity. As you move far away from the swarming stars of the inner galaxy, gravity becomes weaker, and so motions become more sedate.

The rotation measurements only stretch 35,000 light years out from the galactic centre, which is not far enough to confirm that first impression. So a team of astronomers in Poland developed a more sophisticated analysis.

Joanna Jalocha, Lukasz Bratek and Marek Kutschera of the Polish Academy of Science in Krakow have found a way to splice the rotation curve together with another measurement: the density of hydrogen gas far from the galactic centre.

According to their combined mathematical model, ordinary luminous stars and gas can indeed account for all the mass in NGC 4736.

Skeptical response

"If this paper is correct, then this galaxy contains very little or no dark matter," says astrophysicist Jürg Diemand of the University of California, Santa Cruz, US, who is not a member of the team. "That is surprising."

Diemand says numerous other techniques – including studies of how galaxies move inside clusters and measurements of the big bang's afterglow – all show evidence for dark matter.

So could the new analysis be faulty? "One really needs excellent data to pull this off," says Stacy McGaugh of the University of Maryland in College Park, US, an expert in galaxy formation and evolution. "I'm afraid my grumpy first impression is that I just don't buy it."

Great puzzle

McGaugh points out that other galaxies have shown declining rotation curves, but later observations have always shown that beyond a certain distance, they flatten out, which can't be explained by ordinary gravity from visible stars and gas. "If we believe this decline, it seems like the exception and not the rule," he says.

Even then, one exceptional dark-matter-less galaxy would be a great puzzle. "The current picture is that galaxies form inside of dark matter halos," Diemand told New Scientist. The dark matter's gravity attracts ordinary gas, which can then coagulate into stars.

"It is unclear how one would form a galaxy without a dark halo, or how one could remove the halo without destroying the galaxy," says Diemand. "A galaxy without dark matter really does not fit into our current understanding of cosmology and galaxy formation."

Nor can galaxies with declining rotation curves be easily explained by MOND, says McGaugh. So for now, it seems that some of our missing mass is missing.

Original Publication: http://space.newscientist.com/channel/astronomy/dn13280-galaxy-without-dark-matter-puzzles-astronomers.html?feedId=astronomy_rss20

posted in Astronomy & Astrophysics - 0 replies

Rogue Stars: The Miscreants of Our Galaxy

2008-01-30T04:59:38Z

By Andrea Thompson
Staff Writer
posted: 29 January 2008
05:51 am ET

A young star speeding away from the Milky Way is in fact an alien visitor, astronomers have confirmed. The wayward object is one of several rogues that are giving astronomers a glimpse into the volatile nature of our galaxy and others.

Astronomers have found about 10 stars hurtling away from our galaxy, at speeds that exceed its gravitational grasp. While most stars rush through space at speeds on the order of hundreds of kilometers per second, these aptly-named "hypervelocity stars", http://www.space.com/scienceastronomy/escaping_star_050208.html , are rocketing away at least twice as fast.

Most of these speedy stars are thought to be exiles from the center of our galaxy, flung out into intergalactic space by the powerful forces of the massive black hole at the center of our galaxy. Their violent creation is giving astronomers insight into the almost impenetrable world at the center of the Milky Way, the mysteries of our nearby galactic neighbors, and the nature of intergalactic space.

Volatile origins

Hypervelocity stars were first theorized to exist in 1988. The theory was that binary star systems at the galaxy's center would occasionally wander too close to the massive black hole, http://www.space.com/scienceastronomy/051102_black_hole.html , looming there, which would disrupt their orbital dance. While one of the pair was captured by the black hole, the other would be sent rocketing off at an incredible speed.

"That's the only way you can accelerate a star to go thousands of kilometers per second," said astronomer Alceste Bonanos of the Carnegie Institution for Science, a member of the team that made the discovery of the alien star's origins.

Of the billions of stars in the Milky Way, only a tiny fraction are thought to be shot out from the center like this. This explains why they weren't found until 2005, Bonanos says, "because there aren't very many."

Astronomers looked at the spectra of stars at the most outer reaches of the Milky Way and found a few that "were going very, very fast, which isn't normal," Bonanos said.

By examining the age of these exiled stars, astronomers concluded that they seem to have had time to come from the center of our galaxy.

The galaxy's center is shrouded in gas and dust and normally hard for astronomers to peer into, Bonanos said. Gas clouds usually act as excellent stellar nurseries, but the violent tidal forces from the black hole were thought to prevent any nearby stellar births.

The rogue stars seem to contradict that idea, as they seem to have come from the vicinity of the black hole, Bonanos told LiveScience.

Except for one, which is an alien passerby.

'Alien' traveler

Of these 10 strange stars, one, dubbed HE 0437-5439, seemed a bit stranger than the rest.

"This one is different from the other nine," said study team member Mercedes Lopez-Morales, also of the Carnegie Institution.

Based on its current position, the star would have to be 100 million years old to have come from the center of the Milky Way, http://www.space.com/milkyway/ . But it is only 35 million years old.

Bonanos and Lopez-Morales took a closer look at the elemental composition of the star and found that it seemed to be a visitor from our small galactic neighbor, the Large Magellanic Cloud (LMC), http://www.space.com/imageoftheday/image_of_day_060110.html .

"Stars in the LMC are known to have lower elemental abundances than most stars in our galaxy," Bonanos explained, which seemed to fit HE 0437-5439's make-up.

But while the elemental profile matched, there's one big conundrum: The LMC "is not known to have a massive black hole that could eject it," Bonanos said.

The usual tell-tale signs of a big black hole, such as strong X-ray and radio signals, are missing. Astronomers aren't sure if dwarf galaxies like the LMC have huge black holes in their center, so "this star might be a hint for something important," Bonanos said.

Collision course?

Another strange consequence of these roving stars is the contradiction they provide to the long-held notion that intergalactic space is pretty much empty.

'There seem to be all these stars flying around between galaxies," Bonanos said. If stars are shot out from our galaxy, they are likely propelled from others, she says, though we are unlikely to be able to see them because stars are too hard to individually identify from the distance of most galaxies.

It is predicted that thousands of hypervelocity stars have been spit out by the Milky Way's black hole, Bonanos said, though many are still hurtling through the galaxy.

So far all of the hypervelocity stars found are moving away, http://www.space.com/scienceastronomy/050906_fast_star.html , from us, but they could be shot out of the galaxy's center in any direction, up or down from the galactic plane, or even toward us.

But there's no need to worry about a stellar roadrunner knocking into Earth, or any other planet or star, Bonanos says.

"There's a lot of empty space" in the solar system, she says, so these speeding stars will likely have a clear path out of the neighborhood.

Original Publication: http://www.space.com/scienceastronomy/080129-st-rogue-stars.html

posted in Astronomy & Astrophysics - 0 replies

Pools of Invisible Matter Mapped in Space

2008-01-17T21:08:13Z

By Jeanna Bryner
Staff Writer
posted: 17 January 2008
06:10 am ET

A new map reveals dense pools of invisible matter tipping the scales at 10 trillion times the mass of the sun and housing a cosmic city of ancient galaxies.

The map, presented last week at a meeting of the American Astronomical Society in Austin, Texas, provides indirect evidence for so-called dark matter and how this mysterious substance affects galaxy formation.

Scientists theorize that dark matter, considered to make up about 85 percent of the universe's matter, acts as scaffolding, http://www.space.com/scienceastronomy/080107-mm-cosmic-web.html , on which galaxies mature. As the universe evolves, the tug from dark matter's gravitational field causes galaxies to collide and swirl into superclusters.

It's all these gravitational effects, from something that can't be seen, that indicates dark matter exists.

"The dark matter halos are what allow the galaxies to form in the first place. The dark matter is the underlying skeleton of the universe," said Meghan Gray of the University of Nottingham in the United Kingdom, who was part of the map-making team. "Most of the universe is dark matter. Galaxies are just froth on this ocean of dark matter."

Uncovering invisible matter

Gray, Catherine Heymans of the University of British Columbia in Vancouver and colleagues used NASA's Hubble Space Telescope to observe a supercluster called Abell 901/902, which resides 2.6 billion light-years from Earth and spans more than 16 million light-years across.

The astrophysicists measured light from a backdrop of more than 60,000 galaxies after it passed through the supercluster and its dark matter, http://www.space.com/php/video/player.php?video_id=150407Dark_matter . According to Einstein's general relativity theory, the presence of matter can bend spacetime, deflecting the path of a light ray passing through the mass.

"Dark matter leaves a signature in distant galaxies" explained study co-author Ludovic Van Waerbeke of the University of British Columbia. "For example, a circular galaxy will become more distorted to resemble the shape of a banana if its light passes near a dense region of dark matter."

By averaging the shape-distortions from the thousands of galaxies, the researchers found four pools of dark matter, http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=080116-abell-cluster-02.jpg&cap=This+Hubble+Space+Telescope+map+shows+the+four+clumps+of+dark+matter+in+the+supercluster+Abell+901%2F902.+Credit%3A+NASA%2C+ESA%2C+C.+Heymans+%28University+of+British+Columbia%29%2C+M.+Gray+%28University+of+Nottingham%29%2C+M.+Barden+%28Innsbruck%29%2C+STAGES+collaboration. . And the invisible clumps matched up with the location of hundreds of ancient galaxies, which have experienced a violent history in their passage from the outskirts of the supercluster into the central hubs.

"If the supercluster wasn't there, you'd still see all of these galaxies in the background," Gray told SPACE.com. "But you put this massive object [in front of them] and your view gets distorted. It's a cosmic optical illusion."

Aging galaxies

The survey's broader goal is to understand how galaxies are influenced by the environment in which they live.

"The new map of the underlying dark matter in the supercluster is one key piece of this puzzle," Gray said. "At the same time, we're looking in detail at the galaxies themselves."

The galaxies, http://www.space.com/php/multimedia/imagegallery/igviewer.php?imgid=3971&gid=286 , in the central hubs, they are finding, show signs of aging, as they are elliptical, red in color and are no longer forming stars. Disk galaxies reside on the outskirts of the supercluster. These youthful galaxies are blue-hued and buzzing with star birth.

It's these young galaxies that constantly fall into the supercluster, adding to its galactic girth.

"As they come in, either they're interacting with each other more or they're interacting with the dark matter," Gray explained. "Something is happening to change their properties."

The team plans to study individual galaxies in an effort to understand how this supercluster environment shapes and changes galaxies.

Original Publication: http://www.space.com/scienceastronomy/080117-aas-dark-matter.html

posted in Astronomy & Astrophysics - 0 replies