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April 25, 2006, 7:27 PM CT

Black Holes Are "Green"

Black Holes Are
Black holes are the most fuel efficient engines in the Universe, as per a new study using NASA's Chandra X-ray Observatory. By making the first direct estimate of how efficient or "green" black holes are, this work gives insight into how black holes generate energy and affect their environment.

The new Chandra finding shows that most of the energy released by matter falling toward a supermassive black hole is in the form of high-energy jets traveling at near the speed of light away from the black hole. This is an important step in understanding how such jets can be launched from magnetized disks of gas near the event horizon of a black hole.

"Just as with cars, it's critical to know the fuel efficiency of black holes," said lead author Steve Allen of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, and the Stanford Linear Accelerator Center. "Without this information, we cannot figure out what is going on under the hood, so to speak, or what the engine can do".

Allen and his team used Chandra to study nine supermassive black holes at the centers of elliptical galaxies. These black holes are relatively old and generate much less radiation than quasars, rapidly growing supermassive black holes seen in the early Universe. The surprise came when the Chandra results showed that these "quiet" black holes are all producing much more energy in jets of high-energy particles than in visible light or X-rays. These jets create huge bubbles, or cavities, in the hot gas in the galaxies.........

Posted by: Edwin      Permalink         Source


April 24, 2006, 7:32 PM CT

Brown Dwarfs Weighed Directly for First Time

Brown Dwarfs Weighed Directly for First Time
Astronomers have made the first direct mass measurements of brown dwarfs by following a pair of the "failed" stars in their cosmic dance around one another. The breakthrough could allow other suspected brown dwarfs to be positively identified.

Brown dwarfs are intermediate objects - too large to be planets, yet too small to be stars. They are sometimes defined as having between 13 and 75 times the mass of Jupiter.........

Posted by: Edwin      Permalink         Source


April 22, 2006, 6:26 PM CT

The Giant Magellan Telescope Group Grows

The Giant Magellan Telescope Group Grows
The Giant Magellan Telescope (GMT), the first extremely large new-generation telescope to begin production, has gained a new partner-the Australian National University (ANU) http://www.anu.edu.au/. The announcement made today comes from the Giant Magellan Telescope consortium. Other consortium members include the Carnegie Observatories, Harvard University, Smithsonian Astrophysical Observatory, University of Arizona, University of Michigan, Massachusetts Institute of Technology, University of Texas at Austin, and Texas A&M University.

"The addition of the Australian National University to the GMT consortium is the most recent indication of the momentum that the project is generating," commented Wendy Freedman, chair of the GMT board and the Crawford H. Greenewalt director of the Carnegie Observatories. "We couldn't be more pleased with ANU's participation. We all share a common goal of probing the most important questions in astronomy facing us over the next generation-the mysteries of dark energy, dark matter, and black holes; the birth of stars and planetary systems in our Milky Way; the genesis of galaxies; and much more".

"The GMT represents a new epoch for astronomy," stated Richard Meserve, president of the Carnegie Institution. "Now, with a group of nine, the consortium is well on its way to accomplishing its goals," he added.........

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April 20, 2006, 10:55 PM CT

Breakthrough In Black Hole Simulation

Breakthrough In Black Hole Simulation This visualization shows what Einstein envisioned. Researchers crunched Einstein's theory of general relativity on the Columbia supercomputer at the NASA Ames Research Center to create a three-dimensional simulation of merging black holes. This was the largest astrophysical calculation ever performed on a NASA supercomputer. The simulation provides the foundation to explore the universe in an entirely new way, through the detection of gravitational waves. (7.4 Mb - no audio). Click on image to view animation. Credit:Henze, NASA
NASA researchers have reached a breakthrough in computer modeling that allows them to simulate what gravitational waves from merging black holes look like. The three-dimensional simulations, the largest astrophysical calculations ever performed on a NASA supercomputer, provide the foundation to explore the universe in an entirely new way.

As per Einstein's math, when two massive black holes merge, all of space jiggles like a bowl of Jell-O as gravitational waves race out from the collision at light speed.

Prior simulations had been plagued by computer crashes. The necessary equations, based on Einstein's theory of general relativity, were far too complex. But researchers at NASA's Goddard Space Flight Center in Greenbelt, Md., have found a method to translate Einstein's math in a way that computers can understand.

"These mergers are by far the most powerful events occurring in the universe, with each one generating more energy than all of the stars in the universe combined. Now we have realistic simulations to guide gravitational wave detectors coming online," said Joan Centrella, head of the Gravitational Astrophysics Laboratory at Goddard.

The simulations were performed on the Columbia supercomputer at NASA's Ames Research Center near Mountain View, Calif. This work appears in the March 26 issue of Physical Review Letters and will appear in an upcoming issue of Physical Review D. The lead author is John Baker of Goddard.........

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April 20, 2006, 0:32 AM CT

Xmm-newton Reveals A Tumbling Neutron Star

Xmm-newton Reveals A Tumbling Neutron Star XMM-Newton image of pulsar 'RX J0720.4-3125'
Using data from ESA's XMM-Newton X-ray observatory, an international group of astrophysicists discovered that one spinning neutron star doesn't appear to be the stable rotator researchers would expect. These X-ray observations promise to give new insights into the thermal evolution and finally the interior structure of neutron stars.

Spinning neutron stars, also known as pulsars, are generally known to be highly stable rotators. Thanks to their periodic signals, emitted either in the radio or in the X-ray wavelength, they can serve as very accurate astronomical 'clocks'.

The researchers found that over the past four and a half years the temperature of one enigmatic object, named RX J0720.4-3125, kept rising. However, very recent observations have shown that this trend reversed and the temperature is now decreasing.

As per the researchers this effect is not due to a real variation in temperature, but instead to a changing viewing geometry. RX J0720.4-3125 is most probably 'precessing', that is it is slowly tumbling and therefore, over time, it exposes to the observers different areas of the surface.

Neutron stars are one of the endpoints of stellar evolution. With a mass comparable to that of our Sun confined into a sphere of 20-40 km diameter, their density is even somewhat higher than that of an atomic nucleus - a billion tonnes per cubic centimetre. Soon after their birth in a supernova explosion their temperature is of the order of 1 000 000 ÂșC and the bulk of their thermal emission falls in the X-ray band of the electromagnetic spectrum. Young isolated neutron stars are slowly cooling down and it takes a million years before they become too cold to be observable in X-rays.........

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April 18, 2006, 11:20 PM CT

Gamma Radiation From The Cosmos Unlikely

Gamma Radiation From The Cosmos Unlikely

Are you losing sleep at night because you're afraid that all life on Earth will suddenly be annihilated by a massive dose of gamma radiation from the cosmos?

Well, now you can rest easy.

Some researchers have wondered whether a deadly astronomical event called a gamma ray burst could happen in a galaxy like ours, but a group of astronomers at Ohio State University and their colleagues have determined that such an event would be nearly impossible.

Gamma ray bursts (GRBs) are high-energy beams of radiation that shoot out from the north and south magnetic poles of a particular kind of star during a supernova explosion, explained Krzysztof Stanek, associate professor of astronomy at Ohio State. Researchers suspect that if a GRB were to occur near our solar system, and one of the beams were to hit Earth, it could cause mass extinctions all over the planet.

The GRB would have to be less than 3,000 light years away to pose a danger, Stanek said. One light year is approximately 6 trillion miles, and our galaxy measures 100,000 light years across. So the event would not only have to occur in our galaxy, but relatively close by, as well.

In the new study, which Stanek and his coauthors submitted to the Astrophysical Journal, they found that GRBs tend to occur in small, misshapen galaxies that lack heavy chemical elements (astronomers often refer to all elements other than the very lightest ones -- hydrogen, helium, and lithium -- as metals). Even among metal-poor galaxies, the events are rare -- astronomers only detect a GRB once every few years.........

Posted by: Edwin      Permalink         Source


April 17, 2006, 10:17 PM CT

Wintering on Mars

Wintering on Mars
NASA's Mars rover Spirit has reached a safe site for the Martian winter, while its twin, Opportunity, is making fast progress toward a destination of its own.

The two rovers recently set out on important -- but very different -- drives after earlier weeks inspecting sites with layers of Mars history. Opportunity finished examining sedimentary evidence of ancient water at a crater called "Erebus," and is now rapidly crossing flat ground toward the scientific lure of a much larger crater, "Victoria."

Spirit studied signs of a long-ago explosion at a bright, low plateau called "Home Plate" during February and March. Then one of its six wheels quit working, and Spirit struggled to complete a short advance to a north-facing slope for the winter. "For Spirit, the priority has been to reach a safe winter haven," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the Mars Exploration Rover project.

The rovers have operated more than eight times as long as their originally planned three-month explorations on Mars. Each has driven more than 6.8 kilometers (4.2 miles) about 11 times as far as planned. Combined, they have returned more than 150,000 images. Two years ago, the project had already confirmed that at least one place on Mars had a wet and possibly habitable environment long ago. The scientific findings continue. ........

Posted by: Edwin      Permalink         Source


April 17, 2006, 10:10 PM CT

Exploding Stars

Exploding Stars
Artist's impression of the explosion of RS Ophiuchi. Image Credit: David A. Hardy.
amateur astronomers reported that a faint star in the constellation of Ophiuchus had suddenly become clearly visible in the night sky without the aid of a telescope. Records show that this so-called recurrent nova, RS Ophiuchi (RS Oph), has previously reached this level of brightness five times in the last 108 years, most recently in 1985. The latest explosion has been observed in unprecedented detail by an armada of space- and ground-based telescopes.

Speaking today (Friday) at the RAS National Astronomy Meeting at Leicester, Professor Mike Bode of Liverpool John Moores University and Dr Tim O'Brien of Jodrell Bank Observatory will present the latest results which are shedding new light on what happens when stars explode.

RS Oph is just over 5,000 light years away from Earth. It consists of a white dwarf star (the super-dense core of a star, about the size of the Earth, that has reached the end of its main hydrogen-burning phase of evolution and shed its outer layers) in close orbit with a much larger red giant star.

The two stars are so close together that hydrogen-rich gas from the outer layers of the red giant is continuously pulled onto the dwarf by its high gravity. After around 20 years, enough gas has been accreted that a runaway thermonuclear explosion occurs on the white dwarf's surface. In less than a day, its energy output increases to over 100,000 times that of the Sun, and the accreted gas (several times the mass of the Earth) is ejected into space at.........

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April 14, 2006, 9:26 AM CT

Peep Into Universe

Peep Into Universe

An image made of about 300 million pixels is being released by ESO, based on more than 64 hours of observations with the Wide-Field Camera on the 2.2m telescope at La Silla (Chile). The image covers an 'empty' region of the sky five times the size of the full moon, opening an exceptionally clear view towards the most distant part of our universe. It reveals objects that are 100 million times fainter than what the unaided eye can see.

Easter is in a number of countries a time of great excitement for children who are on the big hunt for chocolate eggs, hidden all about the places. Astronomers, however, do not need to wait this special day to get such an excitement: it is indeed daily that they look for faraway objects concealed in deep images of the sky. And as with chocolate eggs, deep sky objects, such as galaxies, quasars or gravitational lenses, come in the wildest variety of colours and shapes.

The image presented here is one of such very deep image of the sky. It is the combination of 714 frames for a total exposure time of 64.5 hours obtained through four different filters (B, V, R, and I)! It consists of four adjacent Wide-Field Camera pointings (each 33x34 arcmin), covering a total area larger than one square degree.

Yet, if you were to look at this large portion of the firmament with the unaided eye, you would just see. nothing. The area, named Deep 3, was indeed chosen to be a random but empty, high galactic latitude field, positioned in such a way that it can be observed from the La Silla observatory all over the year.........

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April 12, 2006, 11:55 PM CT

U.S.-Taiwan Constellation Of Satellites

U.S.-Taiwan Constellation Of Satellites We have liftoff. COSMIC satellites will take to the atmosphere this week. Credit: University Corporation for Atmospheric Research/National Center for Atmospheric Research
A globe-spanning constellation of six satellites expected to improve weather forecasts, monitor climate change, and enhance space weather research will head into orbit on Fri. April 14, 2006. Barring delays, a Minotaur rocket is scheduled to launch the array at 5:10 p.m. Pacific time from Vandenberg Air Force Base on the central Calif. coast.

The low-orbiting satellites will be the first to provide atmospheric data daily in real time over thousands of points on Earth for both research and operational weather forecasting. The satellites will measure the bending of radio signals from the U.S. Global Positioning System (GPS) as the signals pass through Earth's atmosphere.

Called COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) in the United States and FORMOSAT-3 in Taiwan, the $100 million satellite network is the product of an agreement between the American Institute in Taiwan and the Taipei Economic and Cultural Representative Office in the United States. The array is based on a system design provided by the University Corporation for Atmospheric Research (UCAR).

Temperature and water vapor profiles derived from the GPS data will help meteorologists observe, research, and forecast hurricanes, typhoons, and other storm patterns over the oceans and improve a number of areas of weather prediction. The stability, consistency, and accuracy of the measurements will provide critical new information to researchers quantifying long-term climate change trends, say atmospheric scientists.........

Posted by: Edwin      Permalink         Source


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