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Archive for the ‘Galaxies’ Category

Scientists At Keck Discover The Fluffiest Galaxies


Credit: P. van Dokkum, R. Abraham, J. Brodie

Credit: P. van Dokkum, R. Abraham, J. Brodie

An international team of researchers led by Pieter van Dokkum at Yale University have used the W. M. Keck Observatory to confirm the existence of the most diffuse class of galaxies known in the universe. These “fluffiest galaxies” are nearly as wide as our own Milky Way galaxy – about 60,000 light years – yet harbor only one percent as many stars. The findings were recently published in the Astrophysical Journal Letters.

“If the Milky Way is a sea of stars, then these newly discovered galaxies are like wisps of clouds”, said van Dokkum. “We are beginning to form some ideas about how they were born and it’s remarkable they have survived at all. They are found in a dense, violent region of space filled with dark matter and galaxies whizzing around, so we think they must be cloaked in their own invisible dark matter ‘shields’ that are protecting them from this intergalactic assault.”

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Cause Of Galactic Death: Strangulation


Artist’s impression. Credit: re-active

Artist’s impression. Credit: re-active

As murder mysteries go, it’s a big one: how do galaxies die and what kills them? A new study, published today in the journal Nature, has found that the primary cause of galactic death is strangulation, which occurs after galaxies are cut off from the raw materials needed to make new stars.

Researchers from the University of Cambridge and the Royal Observatory Edinburgh have found that levels of metals contained in dead galaxies provide key ‘fingerprints’, making it possible to determine the cause of death.

There are two types of galaxies in the Universe: roughly half are ‘alive’ galaxies which produce stars, and the other half are ‘dead’ ones which don’t. Alive galaxies such as our own Milky Way are rich in the cold gas – mostly hydrogen – needed to produce new stars, while dead galaxies have very low supplies. What had been unknown is what’s responsible for killing the dead ones.

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Hubble Finds Massive Halo Around The Andromeda Galaxy


University of Notre Dame astrophysicist Nicolas Lehner has led a team of scientists who have used NASA’s Hubble Space Telescope to identify an immense halo of gas surrounding the Andromeda Galaxy, the nearest major galaxy to Earth. The halo stretches about a million light-years from Andromeda, halfway to the Milky Way. The discovery will tell astronomers more about the evolution and structure of giant spiral galaxies such as the Milky Way and Andromeda.

“Halos are the gaseous atmospheres of galaxies,” said Lehner, the lead investigator. “The properties of these gaseous halos control the rate at which stars form in galaxies.” The gargantuan halo is estimated to contain at least as much mass in its diffuse gas as half of the stars in the Andromeda Galaxy.

The Andromeda Galaxy, also known as Messier 31 or M31, is the most massive galaxy in the Local Group of galaxies that also includes the Milky Way and about 45 other known galaxies. M31 contains one trillion stars, about double the number of stars in the Milky Way. It is estimated to be about 25 percent more luminous than the Milky Way and lies 2.5 million light-years away.

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How A New Telescope Will Measure The Expansion Of The Universe


For the past several years, scientists at the U.S. Department of Energy’s Lawrence Berkeley National Lab (Berkeley Lab) have been planning the construction of and developing technologies for a very special instrument that will create the most extensive three-dimensional map of the universe to date. Called DESI for Dark Energy Spectroscopic Instrument, this project will trace the growth history of the universe rather like the way you might track your child’s height with pencil marks climbing up a doorframe. But DESI will start from the present and work back into the past.

DESI will make a full 3D map pinpointing galaxies’ locations across the universe. The map, unprecedented in its size and scope, will allow scientists to test theories of dark energy, the mysterious force that appears to cause the accelerating expansion and stretching of the universe first discovered in observations of supernovae by groups led by Saul Perlmutter at Berkeley Lab and by Brian Schmidt, now at Australian National University, and Adam Riess, now at Johns Hopkins University.

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A New, Public View Of The Sky

January 8, 2015 Leave a comment

Photo: Adam Block and Vic Eden/Mount Lemmon SkyCenter/UA

Photo: Adam Block and Vic Eden/Mount Lemmon SkyCenter/UA

For the first time, scientists and the public are beginning to see the large-scale structure of the universe, thanks to the Sloan Digital Sky Survey. UA scientists provide scientific expertise and crucial technology to the largest project ever undertaken to map the cosmos.

On Jan. 6, the Sloan Digital Sky Survey issued its latest public data release, the final release of the third epoch of the survey. Weighing in at more than 100 Terabytes, “Data Release 12” (DR12) contains measurements of the properties of nearly half a billion stars and galaxies, making it one of the largest and richest databases in the history of astronomy.

“The most astonishing feature of the SDSS is the breadth of ground-breaking research it enables,” said Daniel Eisenstein of the Harvard-Smithsonian Center for Astrophysics, the director of SDSS-III. Eisenstein started the survey during his tenure as a professor at the UA’s Steward Observatory, one of the survey’s partner institutions.

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Unusual Light Signal Yields Clues About Elusive Black Hole Merger

January 8, 2015 Leave a comment

Credit: Santiago Lombeyda/Caltech Center for Data-Driven Discovery

Credit: Santiago Lombeyda/Caltech Center for Data-Driven Discovery

The central regions of many glittering galaxies, our own Milky Way included, harbor cores of impenetrable darkness—black holes with masses equivalent to millions, or even billions, of suns. What is more, these supermassive black holes and their host galaxies appear to develop together, or “co-evolve.” Theory predicts that as galaxies collide and merge, growing ever more massive, so too do their dark hearts.

Black holes by themselves are impossible to see, but their gravity can pull in surrounding gas to form a swirling band of material called an accretion disk. The spinning particles are accelerated to tremendous speeds and release vast amounts of energy in the form of heat and powerful X-rays and gamma rays. When this process happens to a supermassive black hole, the result is a quasar—an extremely luminous object that outshines all of the stars in its host galaxy and that is visible from across the universe. “Quasars are valuable probes of the evolution of galaxies and their central black holes,” says George Djorgovski, professor of astronomy and director of the Center for Data-Driven Discovery at Caltech.

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Galactic Herding: New Image Brings Galaxy Diversity To Life

January 5, 2015 Leave a comment

 Image credit: Gemini Observatory/AURA

Image credit: Gemini Observatory/AURA

Galaxy groups are the most evident structures in the nearby universe. They are important laboratories for studying how galaxies form and evolve beyond our own Local Group of galaxies, which includes the Milky Way and the Great Spiral in Andromeda. Exploring the nature of these extragalactic “herds” may help to unlock the secrets to the overall structure of the universe.

Unlike animal herds, which are generally the same species traveling together, most galaxies move through space in associations comprised of myriad types, shapes, and sizes. Galaxy groups differ in their richness, size, and internal structure as well as the ages of their members. Some group galaxies are composed mainly of ancient stars, while others radiate with the power and splendor of youth.

These facts raise important questions for astronomers: Do all the galaxies in a group share a common origin? Are some just chance alignments? Or do galaxy groups pick up “strays” along the way and amalgamate them into the group?

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