Tag Archives: galaxies

The Search for Seeds of Black Holes

How do you grow a supermassive black hole that is a million to a billion times the mass of our sun? Astronomers do not know the answer, but a new study using data from NASA’s Wide-field Infrared Survey Explorer, or WISE, has turned up what might be the cosmic seeds from which a black hole will sprout. The results are helping scientists piece together the evolution of supermassive black holes — powerful objects that dominate the hearts of all galaxies.

Growing a black hole is not as easy as planting a seed in soil and adding water. The massive objects are dense collections of matter that are literally bottomless pits; anything that falls in will never come out. They come in a range of sizes. The smallest, only a few times greater in mass than our sun, form from exploding stars. The biggest of these dark beasts, billions of times the mass of our sun, grow together with their host galaxies over time, deep in the interiors. But how this process works is an ongoing mystery. (more…)

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New dark matter detector begins search for invisible particles

Scientists heard their first pops last week in an experiment that searches for signs of dark matter in the form of tiny bubbles.

They will need to analyze them further in order to discern whether dark matter caused any of the COUPP-60 experiment’s first bubbles at the SNOLAB underground science laboratory in Ontario, Canada. Dark matter accounts for nearly 90 percent of all matter in the universe, yet it is invisible to telescopes.

“Our goal is to make the most sensitive detector to see signals of particles that we don’t understand,” said Hugh Lippincott, a postdoctoral scientist with Fermi National Accelerator Laboratory. Lippincott has spent much of the past several months leading the installation of the one-of-a-kind detector at SNOLAB, 1.5 miles underground. (more…)

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How Galaxies Grow Up

A study of 544 star-forming galaxies shows that disk galaxies like our own Milky Way reached their current state as orderly rotating pinwheels much later than previously thought, long after much of the universe’s star formation had ceased.

Galaxies are in no hurry to grow up, a team of astronomers has discovered. A comprehensive study of hundreds of galaxies observed by the Keck telescopes in Hawaii and NASA’s Hubble Space Telescope has revealed an unexpected pattern of change that extends back 8 billion years, or more than half the age of the universe.

Researchers say the distant blue galaxies they studied are gradually transforming into rotating disk galaxies like our own Milky Way. Until now, it had not been clear how a galaxy’s organization and internal motion change over time, said Benjamin Weiner, assistant astronomer at the UA Steward Observatory and co-author of the paper describing the findings, which are published in The Astrophysical Journal. (more…)

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A Half-Billion Stars And Galaxies From NASA’s WISE Mission Revealed — Many For First Time

A new atlas and catalog of the entire infrared sky with more than a half-billion stars, galaxies and other objects captured by NASA’s Wide-field Infrared Survey Explorer (WISE) mission was unveiled by NASA Wednesday.

“Today WISE delivers the fruit of 14 years of effort to the astronomical community,” said Edward L. (Ned) Wright, a UCLA professor of physics and astronomy and the mission’s principal investigator, who began working on the mission in 1998. (more…)

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Physicists Set Strongest Limit on Mass of Dark Matter

*Brown University physicists have set the strongest limit for the mass of dark matter, the mysterious particles believed to make up nearly a quarter of the universe. The researchers report in Physical Review Letters that dark matter must have a mass greater than 40 giga-electron volts. The distinction is important because it casts doubt on recent results from underground experiments that have reported detecting dark matter.*

PROVIDENCE, R.I. [Brown University] — If dark matter exists in the universe, scientists now have set the strongest limit to date on its mass.

In a paper to be published on Dec. 1 in Physical Review Letters (available in pdf), Brown University assistant professor Savvas Koushiappas and graduate student Alex Geringer-Sameth report that dark matter must have a mass greater than 40 giga-electron volts in dark-matter collisions involving heavy quarks. (The masses of elementary particles are regularly expressed in term of electron volts.) Using publicly available data collected from an instrument on NASA’s Fermi Gamma-ray Space Telescope and a novel statistical approach, the Brown pair constrained the mass of dark matter particles by calculating the rate at which the particles are thought to cancel each other out in galaxies that orbit the Milky Way galaxy. (more…)

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X-Ray Telescope Finds New Voracious Black Holes in Early Universe

ANN ARBOR, Mich.— Using the deepest X-ray image ever taken, a University of Michigan astronomer and her colleagues have found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA’s Chandra X-ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies.

By pointing Chandra at a patch of sky for over six weeks, astronomers obtained what is known as the Chandra Deep Field South (CDFS). When combined with very deep optical and infrared images from NASA’s Hubble Space Telescope, the new Chandra data allowed astronomers to search for black holes in 200 distant galaxies, from when the universe was between about 800 million and 950 million years old. (more…)

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‘Dead’ Galaxies Aren’t So Dead After All

ANN ARBOR, Mich.— University of Michigan astronomers examined old galaxies and were surprised to discover that they are still making new stars. The results provide insights into how galaxies evolve with time.

U-M research fellow Alyson Ford and astronomy professor Joel Bregman presented their findings May 31 at a meeting of the Canadian Astronomical Society in London, Ontario. (more…)

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NASA Telescope Helps Confirm Nature of Dark Energy

PASADENA, Calif. — A five-year survey of 200,000 galaxies, stretching back seven billion years in cosmic time, has led to one of the best independent confirmations that dark energy is driving our universe apart at accelerating speeds. The survey used data from NASA’s space-based Galaxy Evolution Explorer and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.

The findings offer new support for the favored theory of how dark energy works — as a constant force, uniformly affecting the universe and propelling its runaway expansion. They contradict an alternate theory, where gravity, not dark energy, is the force pushing space apart. According to this alternate theory, with which the new survey results are not consistent, Albert Einstein’s concept of gravity is wrong, and gravity becomes repulsive instead of attractive when acting at great distances. (more…)

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