Universe Today » Cosmology

Dark Matter in Distant Galaxy Groups Mapped for the First Time

Jean Tate — Sun, 21 Feb 2010 18:17:07 +0000

X-ray emission in the COSMOS field (XMM-Newton/ESA)

Galaxy density in the Cosmic Evolution Survey (COSMOS) field, with colors representing the redshift of the galaxies, ranging from redshift of 0.2 (blue) to 1 (red). Pink x-ray contours show the extended x-ray emission as observed by XMM-Newton.

Dark matter (actually cold, dark – non-baryonic – matter) can be detected only by its gravitational influence. In clusters and groups of galaxies, that influence shows up as weak gravitational lensing, which is difficult to nail down. One way to much more accurately estimate the degree of gravitational lensing – and so the distribution of dark matter – is to use the x-ray emission from the hot intra-cluster plasma to locate the center of mass.

And that's just what a team of astronomers have recently done … and they have, for the first time, given us a handle on how dark matter has evolved over the last many billion years.
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© Jean Tate for Universe Today, 2010. | Permalink | 7 comments | Add to del.icio.us
Post tags: clusters, X-ray astronomy, XMM-Newton

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ESA's Tough Choice: Dark Matter, Sun Close Flyby, Exoplanets (Pick Two)

Jean Tate — Sun, 21 Feb 2010 01:30:45 +0000

Key questions relevant to fundamental physics and cosmology, namely the nature of the mysterious dark energy and dark matter (Euclid); the frequency of exoplanets around other stars, including Earth-analogs (PLATO); take the closest look at our Sun yet possible, approaching to just 62 solar radii (Solar Orbiter) … but only two! What would be your picks?

These three mission concepts have been chosen by the European Space Agency's Science Programme Committee (SPC) as candidates for two medium-class missions to be launched no earlier than 2017. They now enter the definition phase, the next step required before the final decision is taken as to which missions are implemented.
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Seven-Year WMAP Results: No, They're NOT Anomalies

Jean Tate — Tue, 09 Feb 2010 20:14:47 +0000

CMB cool fingers, cold spots I and II (red; credit: NASA/WMAP Science Team)

Since the day the first Wilkinson Microwave Anisotropy Probe (WMAP) data were released, in 2003, all manner of cosmic microwave background (CMB) anomalies have been reported; there's been the cold spot that might be a window into a parallel universe, the "Axis of Evil", pawprints of local interstellar neutral hydrogen, and much, much more.

But do the WMAP data really, truly, absolutely contain evidence of anomalies, things that just do not fit within the six-parameters-and-a-model the WMAP team recently reported?

In a word, no.
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© Jean Tate for Universe Today, 2010. | Permalink | 12 comments | Add to del.icio.us
Post tags: anomalies, CMB, Cold Spot, WMAP

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Universe to WMAP: ΛCDM Rules, OK?

Jean Tate — Mon, 08 Feb 2010 08:47:12 +0000

Temperature and polarization, CMB hot and cold spots (Credit: NASA/WMAP Science Team)

The Wilkinson Microwave Anisotropy Probe (WMAP) science team has finished analyzing seven full years' of data from the little probe that could, and once again it seems we can sum up the universe in six parameters and a model.

Using the seven-year WMAP data, together with recent results on the large-scale distribution of galaxies, and an updated estimate of the Hubble constant, the present-day age of the universe is 13.75 (plus-or-minus 0.11) billion years, dark energy comprises 72.8% (+/- 1.5%) of the universe's mass-energy, baryons 4.56% (+/- 0.16%), non-baryonic matter (CDM) 22.7% (+/- 1.4%), and the redshift of reionization is 10.4 (+/- 1.2).

In addition, the team report several new cosmological constraints – primordial abundance of helium (this rules out various alternative, 'cold big bang' models), and an estimate of a parameter which describes a feature of density fluctuations in the very early universe sufficiently precisely to rule out a whole class of inflation models (the Harrison-Zel'dovich-Peebles spectrum), to take just two – as well as tighter limits on many others (number of neutrino species, mass of the neutrino, parity violations, axion dark matter, …).
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© Jean Tate for Universe Today, 2010. | Permalink | 7 comments | Add to del.icio.us
Post tags: big bang theory, CMB, Inflation Theory, WMAP

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Searching for Life in the Multiverse

Nancy Atkinson — Mon, 18 Jan 2010 21:39:25 +0000

Artist concept of the multiverse. Credit: Florida State University

Other intelligent and technologically capable alien civilizations may exist in our Universe, but the problems with finding and communicating with them is that they are simply too far away for any meaningful two-way conversations. But what about the prospect of finding if life exists in other universes outside of our own?
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The Extremely Large Telescope

Robert Simpson — Mon, 23 Nov 2009 21:38:14 +0000

The European Southern Observatory (ESO) is planning on building a massive – and I do mean massive – telescope in the next decade. The European Extremely Large Telescope (E-ELT) is a 42-meter telescope in its final planning stages. Weighing in at 5,000 tonnes, and made up of 984 individual mirrors, it will be able to image the discs of extrasolar planets and resolve individual stars in galaxies beyond the Local Group! By 2018 ESO hope to be using this gargantuan scope to stare so deep into space that they can actually see the Universe expanding!(...)
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© rsimp for Universe Today, 2009. | Permalink | 22 comments | Add to del.icio.us
Post tags: extremely large telescope, telescope, Telescopes

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Early Galaxy Pinpoints Reionization Era

Nancy Atkinson — Fri, 06 Nov 2009 19:17:46 +0000

This is a composite of false color images of the galaxies found at the early epoch around 800 million years after the Big Bang. The upper left panel presents the galaxy confirmed in the 787 million year old universe. These galaxies are in the Subaru Deep Field. Credit: M. Ouchi et al.

Astronomers looking to pinpoint when the reionozation of the Universe took place have found some of the earliest galaxies about 800 million years after the Big Bang. 22 early galaxies were found using a method that looks for far-away redshifting sources that disappear or "drop-out" at a specific wavelength. The age of one galaxy was confirmed by a characteristic neutral hydrogen signature at 787 million years after the Big Bang. The finding is the first age-confirmation of a so-called dropout galaxy at that distant time and pinpoints when the reionization epoch likely began.
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New CMB Measurements Support Standard Model

Nicholos Wethington — Wed, 04 Nov 2009 15:31:10 +0000

New measurements of the cosmic microwave background (CMB) – the leftover light from the Big Bang – lend further support the Standard Cosmological Model and the existence of dark matter and dark energy, limiting the possibility of alternative models of the Universe. Researchers from Stanford University and Cardiff University produced a detailed map of the composition and structure of matter as it would have looked shortly after the Big Bang, which shows that the Universe would not look as it does today if it were made up solely of 'normal matter'.(...)
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If We Live in a Multiverse, How Many Are There?

Nancy Atkinson — Thu, 15 Oct 2009 15:12:08 +0000

Artist concept of the cyclic universe.

Theoretical physics has brought us the notion that our single universe is not necessarily the only game in town. Satellite data from WMAP, along with string theory and its 11- dimensional hyperspace idea has produced the concept of the multiverse, where the Big Bang could have produced many different universes instead of a single uniform universe. The idea has gained popularity recently, so it was only a matter of time until someone asked the question of how many multiverses could possibly exist. The number, according to two physicists, could be "humongous."
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Planck First Light

Nancy Atkinson — Thu, 17 Sep 2009 14:03:39 +0000

Strips of the sky measured by Planck. Credit: ESA

One of the newest telescopes in space, the Planck spacecraft, recently completed its "first light" survey which began on August 13. Astronomers say the initial data, gathered from Planck's vantage point at the L2 point in space, is excellent. Planck is studying the Cosmic Microwave Background, looking for variations in temperature that are about a million times smaller than one degree. This is comparable to measuring from Earth the body heat of a rabbit sitting on the Moon.
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What! No Parallel Universe? Cosmic Cold Spot Just Data Artifact

Nancy Atkinson — Wed, 16 Sep 2009 14:18:27 +0000

Region in space detected by WMAP cooler than its surroundings. But not really. Rudnick/NRAO/AUI/NSF, NASA.

Rats! Another perplexing space mystery solved by science. New analysis of the famous "cold spot" in the cosmic microwave background reveals, and confirms, actually, that the spot is just an artifact of the statistical methods used to find it. That means there is no supervoid lurking in the CMB, and no parallel universe lying just beyond the edge of our own. What fun is that?
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© nancy for Universe Today, 2009. | Permalink | 15 comments | Add to del.icio.us
Post tags: CMB, Cold Spot, Cosmology, WMAP

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The Big Bang Writ Little

Nancy Atkinson — Fri, 11 Sep 2009 14:26:28 +0000

If you are into Twitter (as I am), you might enjoy this: New Scientist challenged their readers to encompass the Big Bang into a Tweet. That means the description of the event that started everything that is needs to be 140 characters or less –and actually it was only 133 characters because to qualify, the Tweet had to include the #sci140 hashtag so the folks at New Scientist could gather them all together. Some went the complete science route by trying to summarize the physics (at least one person fit in the equation for Hubble's Law), others quoted ("In the beginning the universe was created. This has made a lot of people very angry and has been widely regarded as a bad move." — Douglas Adams), others took a religious bend, and still others described the event in how it might sound (boom, bang, kaboom or tweeeet). Here's my favorite:

@newscientist < ∞ #sci140 yanikproulx

A fun exercise in brevity.

Here's the rest of their top 10:

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New Way to Measure Curvature of Space Could Unite Gravity Theory

Nancy Atkinson — Tue, 01 Sep 2009 23:10:10 +0000

The curvature of space due to gravity.

Einstein's general theory of relativity describes gravity in terms of the geometry of both space and time. Far from a source of gravity, such as a star like our sun, space is "flat" and clocks tick at their normal rate. Closer to a source of gravity, however, clocks slow down and space is curved. But measuring this curvature of space is difficult. However, scientists have now used a continent-wide array of radio telescopes to make an extremely precise measurement of the curvature of space caused by the Sun's gravity. This new technique promises to contribute greatly in studying quantum physics.
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New Limits on Gravitational Waves From the Big Bang

Nancy Atkinson — Wed, 19 Aug 2009 18:48:30 +0000

Artists concept of graviational waves. Credit: NASA

The only way to know what the Universe was like at the moment of the Big Bang requires analysis of gravitational waves created when the Universe began. Scientists working with the Laser Interferometer Gravitational-Wave Observatory (LIGO) say their initial investigations of these gravitiation waves have turned up nothing. But that's a good thing. Not detecting the waves provides constraints about the initial conditions of the universe, and narrows the field of where we actually do need to look in order to find them.
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What If There Is Only One Universe?

Brian Ventrudo — Thu, 04 Jun 2009 23:28:24 +0000

When it comes to universes, perhaps one is enough after all.

Many theories in physics and cosmology require the existence of alternate, or parallel, universes. But Dr. Lee Smolin of the Perimeter Institute for Theoretical Physics in Waterloo, Canada, explains the flaws of theories that suggest our universe is just one of many, and which also perpetuate the notion that time does not exist. Smolin, author of the bestselling science book 'The Trouble with Physics' and a founding member of the Perimeter Institute, explains his views in the June issue of Physics World.

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Cosmologists Improve on Standard Candles Measurement

Nancy Atkinson — Tue, 19 May 2009 16:55:22 +0000

The warm colors in this diagram stand for strong correlations of the brightness ratios between two wavelengths and a Type Ia supernova's absolute magnitude. Credit: Nearby Supernova Factory

Cosmologists have found a new and quicker technique that establishes the intrinsic brightness of Type Ia supernovae more accurately than ever before. These exploding stars are the best standard candles for measuring cosmic distances and are the tools that made the discovery of dark energy possible. An international team has found a way to do the job of measuring stellar distances in just a single night as opposed to months of observations by simply measuring the ratio of the flux (visible power, or brightness) between two specific regions in the spectrum of a Type Ia supernova. With this new method, a supernova's distance can be determined to better than 6 percent uncertainty.
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Astronomers Closing in on Dark Energy with Refined Hubble Constant

Nancy Atkinson — Thu, 07 May 2009 14:39:32 +0000

The name "dark energy" is just a placeholder for the force — whatever it is — that is causing the Universe to expand. But astronomers are perhaps getting closer to understanding this force. New observations of several Cepheid variable stars by the Hubble Space Telescope has refined the measurement of the Universe's present expansion rate to a precision where the error is smaller than five percent. The new value for the expansion rate, known as the Hubble constant, or H0 (after Edwin Hubble who first measured the expansion of the universe nearly a century ago), is 74.2 kilometers per second per megaparsec (error margin of ± 3.6). The results agree closely with an earlier measurement gleaned from Hubble of 72 ± 8 km/sec/megaparsec, but are now more than twice as precise.
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New Hubble Survey Supports Cold Dark Matter in Early Universe

Nancy Atkinson — Thu, 23 Apr 2009 20:09:35 +0000

NICMOS Image of the GOODS North field. Credit: C Conselice, A Bluck, GOODS NICMOS Team.

A new survey is revealing how the most massive galaxies formed in the early Universe, and the findings support the theory that Cold Dark Matter played a role. A team of scientists from six countries used the NICMOS near infrared camera on the Hubble Space Telescope to carry out the deepest ever survey of its type at near infrared wavelengths. Early results show that the most massive galaxies, which have masses roughly 10 times larger than the Milky Way, were involved in significant levels of galaxy mergers and interactions when the Universe was just 2-3 billion years old.
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Kepler Will Be Used to Measure the Size of the Universe

Ian O'Neill — Tue, 14 Apr 2009 10:30:59 +0000

Artist's rendering of the Kepler Mission (NASA)

On April 7th, commands were sent to NASA's exoplanet-hunting Kepler telescope to eject the 1.3×1.7 metre lens cap so the unprecedented mission could begin its hunt for Earth-like alien worlds orbiting distant stars. However, one UK astronomer won't be using the Kepler data to detect the faint transits of rocky exoplanets in front of their host stars. He'll be using it to monitor the light from a special class of variable star, and through the extreme precision of Kepler's optics he will be joining an international team of collaborators to redefine the size of the Universe…
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Cosmologists Search for Gravity Waves to Prove Inflation Theory

Nancy Atkinson — Mon, 16 Feb 2009 15:19:35 +0000

The South Pole Telescope under the aurora australis (southern lights). Photo by Keith Vanderlinde

During the next decade, cosmologists will attempt to observe the first moments of the Universe, hoping to prove a popular theory. They'll be searching for extremely weak gravity waves to measure primordial light, looking for convincing evidence for the Cosmic Inflation Theory, which proposes that a random, microscopic density fluctuation in the fabric of space and time gave birth to the Universe in a hot big bang approximately 13.7 billion years ago. A new instrument called a polarimeter is being attached to the South Pole Telescope (SPT), which operates at submillimeter wavelengths, between microwaves and the infrared on the electromagnetic spectrum. Einstein's theory of general relativity predicts that Cosmic Inflation should produce the weak gravity waves.
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Cosmologists Look Back to Cosmic Dawn

Nancy Atkinson — Wed, 11 Feb 2009 01:49:35 +0000

The Universe 590 million years after the Big Bang. Credit: Alvaro Orsi, Institute for Computational Cosmology, Durham University.

What did the Universe look like early in its history, only 500 million years after the Big Bang? Currently, we have no way of actually "looking" back that far with our telescopes, but cosmologists from Durham University in the UK have used a computer simulation to predict how the very early Universe would have appeared. The images portray the "Cosmic Dawn," and calculate the formation of the first big galaxies. The simulation also attempts to discern the role that dark matter played in galaxy formation. "We are effectively looking back in time and by doing so we hope to learn how galaxies like our own were made and to understand more about dark matter," said Alvaro Orsi, lead author of the study from Durham University's Institute for Computational Cosmology (ICC). "The presence of dark matter is the key to building galaxies – without dark matter we wouldn't be here today."
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Next-Generation Telescope Gets Team

Anne Minard — Sun, 08 Feb 2009 02:26:58 +0000

Artist's rendering of the Giant Magellan Telescope and support facilities at Las Campanas Observatory, Chile, high in the Andes Mountains. Photo by Todd Mason/Mason Productions

Astronomy organizations in the United States, Australia and Korea have signed on to build the largest ground-based telescope in the world – unless another team gets there first. The Giant Magellan Telescope, or GMT, will have the resolving power of a single 24.5-meter (80-foot) primary mirror, which will make it three times more powerful than any of the Earth's existing ground-based optical telescopes. Its domestic partners include the Carnegie Institution for Science, Harvard University, the Smithsonian Institution, Texas A & M University, the University of Arizona, and the University of Texas at Austin. Although the telescope has been in the works since 2003, the formal collaboration was announced Friday.
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Space Telescope of the Future: SIM

Nancy Atkinson — Tue, 20 Jan 2009 14:52:57 +0000

Artist's concept of the current mission configuration. Credit: JPL

Two of the hottest and most engaging topics in space and astronomy these days are 1.) exoplanets – planets orbiting other stars – and 2.) dark matter—that unknown stuff that seemingly makes up a considerable portion of our universe. There's a spacecraft currently in development that could help answer our questions about whether there really are other Earth-like planets out there, as well as provide clues to the nature of dark matter. The spacecraft is called SIM – the Space Interferometry Mission. "We'll be looking for other Earths around other stars," said Stephen Edberg, System Scientist for the mission, "and by making accurate mass measurements of galaxies, we should be able to measure dark matter, as well."

Listen to the January 20, 2009 "365 Days of Astronomy" Podcast and my interview with Steve Edberg, and/or read more about the SIM Lite mission below!
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Profiling Potential Supernovae

Nancy Atkinson — Mon, 12 Jan 2009 21:19:05 +0000

Astronomical plate showing Sagittarius. Credit: Ashley Pagnotta

Just as psychologists and detectives try to "profile" serial killers and other criminals, astronomers are trying to determine what type of star system will explode as a supernova. While criminals can sometimes be caught or rehabilitated before they do the crime, supernovae, well, there's no stopping them. But there's the potential of learning a great deal in both astronomy and cosmology by theorizing about potential stellar explosions. At the American Astronomical Society meeting last week, Professor Bradley E. Schaefer of Louisiana State University, Baton Rouge, discussed how searching through old astronomical archives can produce unique and front-line science about supernovae – as well as providing information about dark energy — in ways that no combination of modern telescopes can provide. Additionally, Schaefer said amateur astronomers can help in the search, too.
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Did Dark Matter Power Early Stars?

Nancy Atkinson — Fri, 02 Jan 2009 23:41:48 +0000

The galaxy cluster Cl 0024+17 (ZwCl0024+1652) as seen by Hubble’s Advanced Camera for Surveys. Credit: NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)

The first stars to light the early universe may have been powered by dark matter, according to a new study. Researchers from the University of Michigan, Ann Arbor call these very first stars "Dark Stars," and propose that dark matter heating provided the energy for these stars instead of fusion. The researchers propose that with a high concentration of dark matter in the early Universe, the theoretical particles called Weakly Interacting Massive Particles(WIMPs), collected inside the first stars and annihilated themselves to produce a heat source to power the stars. "We studied the behavior of WIMPs in the first stars," said Katherine Freese and her team in their paper, "and found that they can radically alter the stellar evolution. The annihilation products of the dark matter inside the star can be trapped and deposit enough energy to heat the star and prevent it from further collapse."
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