Archive for November, 2012

Biggest Black Hole Blast Discovered

November 28, 2012 Leave a comment

Astronomers using ESO’s Very Large Telescope (VLT) have discovered a quasar with the most energetic outflow ever seen, at least five times more powerful than any that have been observed to date. Quasars are extremely bright galactic centres powered by supermassive black holes. Many blast huge amounts of material out into their host galaxies, and these outflows play a key role in the evolution of galaxies. But, until now, observed quasar outflows weren’t as powerful as predicted by theorists.

Quasars are the intensely luminous centres of distant galaxies that are powered by huge black holes. This new study has looked at one of these energetic objects — known as SDSS J1106+1939 — in great detail, using the X-shooter instrument on ESO’s VLT at the Paranal Observatory in Chile [1]. Although black holes are noted for pulling material in, most quasars also accelerate some of the material around them and eject it at high speed.

“We have discovered the most energetic quasar outflow known to date. The rate that energy is carried away by this huge mass of material ejected at high speed from SDSS J1106+1939 is at least equivalent to two million million times the power output of the Sun. This is about 100 times higher than the total power output of the Milky Way galaxy — it’s a real monster of an outflow,” says team leader Nahum Arav (Virginia Tech, USA). “This is the first time that a quasar outflow has been measured to have the sort of very high energies that are predicted by theory.”

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Can Life Emerge On Planets Around Cooling Stars?

November 28, 2012 Leave a comment

Astronomers find planets in strange places and wonder if they might support life. One such place would be in orbit around a white or brown dwarf. While neither is a star like the sun, both glow and so could be orbited by planets with the right ingredients for life.

No terrestrial, or Earth-like planets have yet been confirmed orbiting white or brown dwarfs, but there is no reason to assume they don’t exist. However, new research by Rory Barnes of the University of Washington and René Heller of Germany’s Leibniz Institute for Astrophysics Potsdam hints that planets orbiting white or brown dwarfs will prove poor candidates for life.

White dwarfs are the hot cores of dead stars and brown dwarfs are failed stars, objects not massive enough to start nuclear burning as the sun does. In theory, both can be bright enough to theoretically support a habitable zone — that swath of space just right for an orbiting planet’s surface water to be in liquid form, thus giving life a chance.

White and brown dwarfs share a common characteristic that sets them apart from normal stars like the sun: They slowly cool and become less luminous over time. And as they cool, their habitable zones gradually shrink inward. Thus, a planet that is found in the center of the habitable zone today must previously have spent time near the zone’s deadly inner edge.

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Planck Spots Hot Gas Bridging Galaxy Cluster Pair

November 28, 2012 Leave a comment

Galaxy clusters connected by gas bridge. Credit: ESA’s Planck Space Telescope

ESA’s Planck space telescope has made the first conclusive detection of a bridge of hot gas connecting a pair of galaxy clusters across 10 million light-years of intergalactic space.

Planck’s primary task is to capture the most ancient light of the cosmos, the Cosmic Microwave Background, or CMB. As this faint light traverses the Universe, it encounters different types of structure including galaxies and galaxy clusters – assemblies of hundreds to thousands of galaxies bound together by gravity.

If the CMB light interacts with the hot gas permeating these huge cosmic structures, its energy distribution is modified in a characteristic way, a phenomenon known as the Sunyaev–Zel’dovich (SZ) effect, after the scientists who discovered it.

This effect has already been used by Planck to detect galaxy clusters themselves, but it also provides a way to detect faint filaments of gas that might connect one cluster to another.

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Astronomers Pin Down Origins Of “Mile Markers” For Expansion Of Universe

November 28, 2012 Leave a comment

A study using a unique new instrument on the world’s largest optical telescope has revealed the likely origins of especially bright supernovae that astronomers use as easy-to-spot “mile markers” to measure the expansion and acceleration of the universe.

In a paper to appear in the Astrophysical Journal, researchers describe observations of recent supernova 2011fe that they captured with the Large Binocular Telescope (LBT) using a tool created at Ohio State University: the Multi-Object Double Spectrograph (MODS). MODS measures the frequencies and intensities of light shining from a star.

Based on the frequencies of light emanating from supernova 2011fe, this type of supernova – known as Type Ia – is most likely caused by the interaction between a pair of dead stars known as white dwarfs, the astronomers concluded. One white dwarf orbits the other and sheds material onto it, until the other white dwarf becomes unstable and explodes, shining billions of times brighter than the sun.

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NOAO: Galaxy Clusters May Offer Critical clues To Dark Energy

November 28, 2012 Leave a comment

In this image the boundary of the cluster of galaxies is marked with a dashed line. Credit: Blanco telescope

One of the major puzzles in astronomy today is the nature of the mysterious force that astronomers have dubbed Dark Energy. And one tool in understanding this force is encoded in the distribution of clusters of galaxies in the Universe. Thus, new work by a team of astronomers that has yielded exquisitely precise distances of a large sample of clusters may lead to breakthroughs in understanding the expansion history of our Universe.

Astronomers have known for over 80 years that our Universe is expanding from an event called the Big Bang. In 2011, the Nobel Prize in physics was awarded for the even more exciting discovery that the rate of expansion is increasing, rather than slowing down as might be expected. The cause of this acceleration, referred to as Dark Energy, is not understood.

As Dr. Jeeseon Song, lead author of the study, remarked: “By looking at galaxy clusters at different epochs in cosmic history, astronomers can explore whether Dark Energy has acted differently at different times in the history of the Universe. Galaxies, including our own Milky Way galaxy, are vast assemblages of stars and gas. Clusters of galaxies, conglomerates of tens to hundreds of galaxies, are the largest structures in the Universe. They are dynamically changing and aging over time. And that is very crucial in cosmological studies, because that’s where we can see how Dark Energy is acting on the Universe, pulling the clusters apart.” By studying the distribution of clusters at different times in the past, astronomers detect what the Dark Energy does to the Universe, allowing them to figure out what the Dark Energy itself is.

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Dwarf Planet Makemake Lacks Atmosphere

November 28, 2012 Leave a comment

Astronomers have used three telescopes at ESO’s observatories in Chile to observe the dwarf planet Makemake as it drifted in front of a distant star and blocked its light. The new observations have allowed them to check for the first time whether Makemake is surrounded by an atmosphere. This chilly world has an orbit lying in the outer Solar System and was expected to have an atmosphere like Pluto, but this is now shown not to be the case. The scientists also measured Makemake’s density for the first time. The new results are to be published in the 22 November issue of the journal Nature.

“As Makemake passed in front of the star and blocked it out, the star disappeared and reappeared very abruptly, rather than fading and brightening gradually. This means that the little dwarf planet has no significant atmosphere,” says José Luis Ortiz. “It was thought that Makemake had a good chance of having developed an atmosphere — that it has no sign of one at all shows just how much we have yet to learn about these mysterious bodies. Finding out about Makemake’s properties for the first time is a big step forward in our study of the select club of icy dwarf planets.

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Failed Explosions Explain Most Peculiar Supernovae

November 21, 2012 Leave a comment

Supercomputer simulations have revealed that a type of oddly dim, exploding star is probably a class of duds—one that could nonetheless throw new light on the mysterious nature of dark energy.

Most of the thousands of exploding stars classified as type Ia supernovae look similar, which is why astrophysicists use them as accurate cosmic distance indicators. They have shown that the expansion of the universe is accelerating under the influence of an unknown force now called dark energy. Yet approximately 20 type Ia supernovae look peculiar.

“They’re all a little bit odd,” said George Jordan, a research scientist at the University of Chicago’s Flash Center for Computational Science. Comparing odd type Ia supernovae to normal ones may permit astrophysicists to more precisely define the nature of dark energy, he noted.

Jordan and three colleagues, including his chief collaborator on the project, Hagai Perets, assistant professor of physics at Technion – Israel Institute of Technology, have found that the peculiar type Ia supernovae are probably white dwarf stars that failed to detonate. “They ignite an ordinary flame and they burn, but that isn’t followed by a triggering of a detonation wave that goes through the star,” Jordan said.

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