Unusually short but intense “fireballs” in the distant universe might be created by the plucking of invisible cosmic strings—ultradense flaws in space-time—a new study suggests. Some gamma-ray bursts stay visible for several seconds to a few minutes. Scientists think these long-duration bursts are created when the cores of very massive stars collapse and explode. Other bursts are much more brief—sometimes lasting just fractions of a second—and it’s unclear what triggers them.
NASA launched a telescope Wednesday to scout out elusive, super high-energy gamma rays lurking in the universe. Glast — a NASA acronym standing for Gamma-ray Large Area Space Telescope — began its five- to 10-year Earth-orbiting mission with a midday blastoff aboard a Delta rocket. The $690 million telescope, supported by six countries, will pick up where NASA’s Compton Gamma Ray Observatory left off before its deliberate destruction in 2000, but in a bigger and better way. In addition to the United States, participating countries include Italy, France, Germany, Sweden and Japan. With superior new technology and insight gained from Compton and other telescopes, Glast will be able to do in three hours, or two orbits of Earth — survey the entire sky — what Compton took 15 months to do. What’s more, Glast and its particle detectors are much more sensitive and precise, and should provide an unprecedented view into the high-energy universe from a 345-mile(555-kilometer)-high orbit.
Site – http://www.cnn.com
For decades, astronomers have pictured our galaxy as sporting four major, spiral arms, however new images effectively sever two appendages, revealing the Milky Way has just two major arms.
“We’re not proposing that they change the positions of the arms,” said Robert Benjamin of the University of Wisconsin, Whitewater. “What we’re proposing is a change in the emphasis of the arms.” Benjamin will present his team’s results today here at a meeting of the American Astronomical Society (AAS).
The findings confirm an earlier observation by a team of astronomers, making a strong case that the Milky Way has two major spiral arms, a common structure for galaxies with bars. These major arms have the greatest densities of both young, bright stars and older, so-called red-giant stars.
Site – http://www.usatoday.com
Reminiscent of how humans used to think the earth was a myriad of shapes and sizes before discovering that it was actually a sphere about 12,742 km in diameter, we are now beginning to have revelations about our universe which may give it a distinct shape and size.
The idea that the universe is finite and relatively small, rather than infinitely large, first became popular in 2003, when cosmologists noticed unexpected patterns in the cosmic microwave background (CMB) – the relic radiation left behind by the Big Bang.The CMB is made up of hot and cold spots that represent ripples in the density of the infant Universe, like waves in the sea. An infinite Universe should contain waves of all sizes, but cosmologists were surprised to find that longer wavelengths were missing from measurements of the CMB made by NASA’s Wilkinson Microwave Anisotropy Probe.
One explanation for the missing waves was that the universe is finite. “You can think of the Universe as a musical instrument – it cannot sustain vibrations that have a wavelength that is bigger than the length of the instrument itself,” explains Frank Steiner, a physicist at Ulm University in Germany.
Larry Sessions, a columnist for Earth & Sky, has suggested in his blog that the gamma-ray event whose radiation reached us a few hours before Arthur C. Clarke died, and which occurred 7.5 billion light-years away, be named the Clarke Event. Even the faintest stars visible to the eye are merely hundreds or thousands of light-years distant, all well within our own Milky Way Galaxy. But staring toward the northern constellation Bootes on March 19th, even without binoculars or telescope you still could have witnessed a faint, brief, flash of light from this gamma-ray burst. The source of that burst has been discovered to lie over halfway across the Universe. The Gamma Ray Burst now holds the distinction of the most distant object that could be seen by the unaided eye and the intrinsically brightest object ever detected, the cosmic explosion is estimated to have been over 2.5 million times more luminous than the brightest known supernova.
Site – http://science.slashdot.org
A telescope arms race is taking shape around the world. Astronomers are drawing up plans for the biggest, most powerful instruments ever constructed, capable of peering far deeper into the universe — and further back in time — than ever before.The building boom, which is expected to play out over the next decade and cost billions of dollars, is being driven by technological advances that afford unprecedented clarity and magnification. Some scientists say it will be much like switching from regular TV to high-definition. In fact, the super-sized telescopes will yield even finer pictures than the Hubble Space Telescope, which was put in orbit in 1990 and was long considered superior because its view was freed from the distorting effects of Earth’s atmosphere. But now, land-based telescopes can correct for such distortion. Just the names of many of the proposed observatories suggest an arms race: the Giant Magellan Telescope, the Thirty Meter Telescope and the European Extremely Large Telescope, which was downsized from the OverWhelmingly Large Telescope. Add to those three big ground observatories a new super eye in the sky, NASA’s James Webb Space Telescope, scheduled for launch in 2013.
Site – http://www.cnn.com
Galaxies and clusters of galaxies are not uniformly distributed in the Universe, instead they collect into vast clusters and sheets and walls of galaxies interspersed with large voids in which very few galaxies seem to exist. The map above shows many of these superclusters including the Virgo supercluster – the fairly minor supercluster of which our galaxy is just a minor member. The entire map is approximately 7 percent of the diameter of the entire visible Universe. Individual galaxies are far too small to appear on this map, each point represents a group of galaxies.
Site – http://www.ldps.ws