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Archive for January, 2014

Active Supermassive Black Holes Revealed In Merging Galaxies

January 29, 2014 Leave a comment

Artist's rendition. Credit: NAOJ

Artist’s rendition. Credit: NAOJ

A team of astronomers has conducted infrared observations of luminous, gas-rich, merging galaxies with the Subaru Telescope to study active, mass-accreting supermassive black holes (SMBHs). They found that at least one SMBH almost always becomes active and luminous by accreting a large amount of material (Figure 1). However, only a small fraction of the observed merging galaxies show multiple, active SMBHs. These results suggest that local physical conditions near SMBHs rather than general properties of galaxies primarily determine the activation of SMBHs.

In this Universe, dark matter has a much higher mass than luminous matter, and it dominates the formation of galaxies and their large-scale structures. The widely accepted, cold-dark-matter based galaxy formation scenario posits that collisions and mergers of small gas-rich galaxies result in the formation of massive galaxies seen in the current Universe. Recent observations show that SMBHs with more than one-million solar masses ubiquitously exist in the center of galaxies. The merger of gas-rich galaxies with SMBHs in their centers not only causes active star formation but also stimulates mass accretion onto the existing SMBHs. When material accretes onto a supermassive black hole (SMBH), the accretion disk surrounding the black hole becomes very hot from the release of gravitational energy, and it becomes very luminous.

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Hubble Helps Solve Mystery Of Ultra-Compact, Burned-Out Galaxies

January 29, 2014 Leave a comment

A certain class of massive galaxies in the early universe lived fast and died young. By “died” astronomers mean that the galaxies had completed building stars just 3 billion years after the big bang. By contrast, our 12-billion-year-old Milky Way galaxy continues making stars today. When star formation stops, the aging stellar population looks redder in the star-forming galaxies that are more bluish. The nickname for the essentially “burned-out” galaxies is “red and dead.”

By combining the power of Hubble with infrared space-based telescopes and ground-based telescopes, astronomers have now solved a decade-long mystery as to how compact elliptical-shaped galaxies existed when the universe was so young. These “red and dead” galaxies have now been linked directly to an earlier population of dusty starburst galaxies. These objects voraciously used up available gas for star formation very quickly. Then they grew slowly through merging as the star formation in them was quenched, and they eventually became giant elliptical galaxies.

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Distant World Gives Clues On Planets

January 29, 2014 Leave a comment

Studies of weather on a distant world – where it rains molten iron – could aid our understanding other solar systems.

Edinburgh researchers have helped map the surface of a brown dwarf – an object larger than a planet and smaller than a star – for the first time.

Scientists say the methods used in their study could eventually be applied to examine small, cool planets in other solar systems.

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‘Rogue’ Asteroids May be The Norm

January 29, 2014 Leave a comment

To get an idea of how the early solar system may have formed, scientists often look to asteroids. These relics of rock and dust represent what today’s planets may have been before they differentiated into bodies of core, mantle, and crust.

In the 1980s, scientists’ view of the solar system’s asteroids was essentially static: Asteroids that formed near the sun remained near the sun; those that formed farther out stayed on the outskirts. But in the last decade, astronomers have detected asteroids with compositions unexpected for their locations in space: Those that looked like they formed in warmer environments were found further out in the solar system, and vice versa. Scientists considered these objects to be anomalous “rogue” asteroids.

But now, a new map developed by researchers from MIT and the Paris Observatory charts the size, composition, and location of more than 100,000 asteroids throughout the solar system, and shows that rogue asteroids are actually more common than previously thought. Particularly in the solar system’s main asteroid belt — between Mars and Jupiter — the researchers found a compositionally diverse mix of asteroids.

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River Of Hydrogen Flowing Through Space Seen With Green Bank Telescope

January 27, 2014 Leave a comment

Credit: D.J. Pisano (WVU); B. Saxton (NRAO/AUI/NSF); Palomar Observatory – Space Telescope Science Institute 2nd Digital Sky Survey (Caltech); Westerbork Synthesis Radio Telescope

Credit: D.J. Pisano (WVU); B. Saxton (NRAO/AUI/NSF); Palomar Observatory – Space Telescope Science Institute 2nd Digital Sky Survey (Caltech); Westerbork Synthesis Radio Telescope

Using the National Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT), astronomer D.J. Pisano from West Virginia University has discovered what could be a never-before-seen river of hydrogen flowing through space. This very faint, very tenuous filament of gas is streaming into the nearby galaxy NGC 6946 and may help explain how certain spiral galaxies keep up their steady pace of star formation.

“We knew that the fuel for star formation had to come from somewhere. So far, however, we’ve detected only about 10 percent of what would be necessary to explain what we observe in many galaxies,” said Pisano. “A leading theory is that rivers of hydrogen – known as cold flows – may be ferrying hydrogen through intergalactic space, clandestinely fueling star formation. But this tenuous hydrogen has been simply too diffuse to detect, until now.”

Spiral galaxies, like our own Milky Way, typically maintain a rather tranquil but steady pace of star formation. Others, like NGC 6946, which is located approximately 22 million light-years from Earth on the border of the constellations Cepheus and Cygnus, are much more active, though less-so than more extreme starburst galaxies. This raises the question of what is fueling the sustained star formation in this and similar spiral galaxies.

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NASA Spacecraft Take Aim At Nearby Supernova

January 27, 2014 Leave a comment

Image Credit: NASA/Swift/P. Brown, TAMU

Image Credit: NASA/Swift/P. Brown, TAMU

An exceptionally close stellar explosion discovered on Jan. 21 has become the focus of observatories around and above the globe, including several NASA spacecraft. The blast, designated SN 2014J, occurred in the galaxy M82 and lies only about 12 million light-years away. This makes it the nearest optical supernova in two decades and potentially the closest type Ia supernova to occur during the life of currently operating space missions.

To make the most of the event, astronomers have planned observations with the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory, Nuclear Spectroscopic Telescope Array (NuSTAR), Fermi Gamma-ray Space Telescope, and Swift missions.

As befits its moniker, Swift was the first to take a look. On Jan. 22, just a day after the explosion was discovered, Swift’s Ultraviolet/Optical Telescope (UVOT) captured the supernova and its host galaxy.

Remarkably, SN 2014J can be seen on images taken up to a week before anyone noticed its presence. It was only when Steve Fossey and his students at the University of London Observatory imaged the galaxy during a brief workshop that the supernova came to light.

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James Webb Space Telescope Passes A Mission Milestone

January 27, 2014 Leave a comment

NASA’s James Webb Space Telescope has passed its first significant mission milestone for 2014 — a Spacecraft Critical Design Review (SCDR) that examined the telescope’s power, communications and pointing control systems.

“This is the last major element-level critical design review of the program,” said Richard Lynch, NASA Spacecraft Bus Manager for the James Webb Space Telescope at NASA’s Goddard Space Flight Center in Greenbelt, Md. “What that means is all of the designs are complete for the Webb and there are no major designs left to do.”

During the SCDR, the details, designs, construction and testing plans, and the spacecraft’s operating procedures were subjected to rigorous review by an independent panel of experts. The week-long review involved extensive discussions on all aspects of the spacecraft to ensure the plans to finish construction would result in a vehicle that enables the powerful telescope and science instruments to deliver their unique and invaluable views of the universe.

“While the spacecraft that carries the science payload for Webb may not be as glamorous as the telescope, it’s the heart that enables the whole mission,” said Eric Smith, acting program director and program scientist for the Webb Telescope at NASA Headquarters in Washington. “By providing many services including telescope pointing and communication with Earth, the spacecraft is our high tech infrastructure empowering scientific discovery.”

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