                  |
 Net World Directory Your personal directory for the internet | ||
| Net World Directory: Archives of astronomy blog |
 | ||
Archives Of Astronomy Blog From NetworlddirectorySubscribe To Astronomy Blog RSS Feed 
Young Supernova Remnants Not Dusty Enough
Recent measurements by University of California, Berkeley, astronomers using infrared cameras aboard NASA's Spitzer Space Telescope show, at most, one-hundredth the amount of dust predicted by current theories of core-collapse supernovae, barely the mass of the planets in the solar system. The discrepancy presents a challenge to researchers trying to understand the origins of stars in the early universe, because dust produced primarily from exploding stars is believed to seed the formation of new-generation stars. While remnants of supermassive exploding stars in the Milky Way galaxy also show less dust than predicted, astronomers had hoped that supernovae in the less-evolved Small Magellanic Cloud would accord more with their models. "Most of the prior work was focused only on our galaxy because we didn't have enough resolution to look further away into other galaxies," said astrophysicist Snezana Stanimirovic, a research associate at UC Berkeley. "But with Spitzer, we can obtain really high resolution observations of the Small Magellanic Cloud, which is 200,000 light years away. Because supernovae in the Small Magellanic Cloud experience conditions similar to those we expect for early galaxies, this is a unique test of dust formation in the early universe"......... Posted by: Brooke Permalink Source Images Contrast Evolution Of Stars
One is a rare type of very massive spectral-type "O" star surrounded by material it ejected in an explosive event earlier in its life that continues to lose mass in a steady "stellar wind." The other is a star originally more similar to our Sun that has lost its outer envelope following a "red giant" phase. It continues to lose mass via a stellar wind as it dies, forming a planetary nebula. The images were made using the Gemini Multi-Object Spectrograph (GMOS) on Gemini South as part of the Gemini Legacy Imaging program. GMOS was built as a joint UK / Canadian effort by the UK Astronomy Technology Centre (UKATC) in Edinburgh, the University of Durham and the Dominion Astrophysical Observatory in Canada. Its creators praise the performance of GMOS. Professor James Dunlop of the University of Edinburgh, current Chair of Gemini Science Committee, said "The Gemini telescope using GMOS is unrivalled in its ability to take stunning images of distant phenomena in our Galaxy and beyond."........ Posted by: Brooke Permalink Source Hundreds Of Young, Distant Galaxy Clusters
The team of astronomers from the University of Florida, NASA's Jet Propulsion Laboratory and the Lawrence Livermore National Laboratory has found nearly 300 new galaxy clusters and groups, including nearly 100 at distances of eight to 10 billion light years. The new sample, a six-fold increase in the number of known clusters and groups at such extreme distances, will allow astronomers to study very young galaxies two-thirds of the way back to when the universe is believed to have originated in the Big Bang. The team will present its findings today in Calgary, Canada, at the American Astronomical Society's biannual meeting. Anthony Gonzalez, an assistant professor of astronomy at UF and one of the team of astronomers who made the discovery, likened the view of the clusters to a glimpse at the Los Angeles basin when it was still home only to a collection of dusty, small towns. By knowing what the clusters looked like eight to 10 billion years ago, the astronomers will have a better idea of where and when the first stars and galaxies formed and how they grew and changed over the universe's full 13.7 billion- year lifespan......... Posted by: Brooke Permalink Source New Orleans Sinking Faster
Satellite images reveal that some areas of the city have been sinking at the rate of 1 inch (2.5 centimeters) a year. The findings, reported in the current issue of the journal Nature, may shed new light on the failure of the city's levee system and the flooding that followed Hurricane Katrina last August. A scientific team used one of Canada's RADARSAT satellites to map New Orleans and found that most of the city sank about a quarter inch (0.06 centimeter) annually in the three years leading up to Katrina's landfall. But a number of areas, including some of the levees designed to hold back the waters of the Gulf of Mexico, sank at four or five times that rate. "What we found is that some of the levee failures in New Orleans were [in] places where subsidence was highest," University of Miami geophysicist Tim Dixon told the Reuters news service. The data suggest that some levees could be 3 feet (0.9 meter) lower than when they were built some 40 years ago. The Mississippi River Gulf Outlet-the levee-protected canal notorious for its role in the flooding that followed Hurricane Katrina-has sunk more than three feet, the team's study reveals......... Posted by: Tyler Permalink Source Finding Fourth Dimension of Space
Charles R. Keeton of Rutgers and Arlie O. Petters of Duke base their work on a recent theory called the type II Randall-Sundrum braneworld gravity model. The theory holds that the visible universe is a membrane (hence "braneworld") embedded within a larger universe, much like a strand of filmy seaweed floating in the ocean. The "braneworld universe" has five dimensions -- four spatial dimensions plus time -- compared with the four dimensions -- three spatial, plus time -- laid out in the General Theory of Relativity. The framework Keeton and Petters developed predicts certain cosmological effects that, if observed, should help scientists validate the braneworld theory. The observations, they said, should be possible with satellites scheduled to launch in the next few years. If the braneworld theory proves to be true, "this would upset the applecart," Petters said. "It would confirm that there is a fourth dimension to space, which would create a philosophical shift in our understanding of the natural world". The scientists' findings appeared May 24, 2006, in the online edition of the journal Physical Review D. Keeton is an astronomy and physics professor at Rutgers, and Petters is a mathematics and physics professor at Duke. Their research is funded by the National Science Foundation......... Posted by: Brooke Permalink Source Images From Akari
Akari's views of galaxy M81
The mission, formerly known as ASTRO-F, was launched on 21 February 2006 (UT) from the Uchinoura Space Centre in Japan. Two weeks after launch the satellite reached its final destination in space - a polar orbit around Earth located at an altitude of approximately 700 kilometres. On 13 April, during the second month of the system checkout and verification of the overall satellite performance, the AKARI telescope's aperture lid was opened and the on-board two instruments commenced their operation. These instruments - the Far Infrared Surveyor (FIS) and the near-mid-infrared camera (IRC) - make possible an all-sky survey in six infrared wavebands. The first beautiful images from the mission have confirmed the excellent performance of the scientific equipment beyond any doubt. AKARI's two instruments were pointed toward the reflection nebula IC4954, a region situated about 6000 light years away, and extending more than 10 light years across space. Reflection nebulae are clouds of dust which reflect the light of nearby stars. In these infrared images of IC4954 a region of intense star formation active for several million years - it is possible to pick out individual stars that have only recently been born. They are embedded in gas and dust and could not be seen in visible light. It is also possible to see the gas clouds from which these stars were actually created......... Posted by: Brooke Permalink Source Lava Tubes On Pavonis Mons
ESA's Mars Express spacecraft obtained this image using the HRSC during orbit 902 with a ground resolution of approximately 14.3 metres per pixel. The image was acquired in the region of Pavonis Mons, at approximately 0.6 degree South and 246.4 degree East. The context map is centred on Pavonis Mons, one of the three volcanoes called Tharsis Montes (the others being Arsia and Ascreus Montes, aligned with Pavonis in a line nearly 1500 km long). Pavonis Mons, rising roughly 12 km above the surrounding plains, is the central volcano of the three 'shield' volcanoes that comprise Tharsis Montes. Gently sloping shield volcanoes are shaped like a flattened dome and are built almost exclusively of lava flows. The dramatic features visible in the colour image are located on the south-west flank of Pavonis Mons. Researchers believe these are lava tubes, channels originally formed by hot, flowing lava that forms a crust as the surface cools. Lava continues to flow beneath this hardened surface, but when the lava production ends and the tunnels empty, the surface collapses, forming elongated depressions. Similar tubes are well known on Earth and the Moon......... Posted by: Brooke Permalink Source Galaxy Formation
Formation sequence (from top left to bottom right) of a Milky-Way type galaxy as obtained form large computer simulations. The galaxy is successively built-up by accretion of satellites. Simulation: Matthias Steinmetz/AIP......... Posted by: Brooke Permalink Source 'Quintuple' Quasar
The most unique feature in this new image taken with the NASA/ESA Hubble Space Telescope is a group of five quasar images produced by a process called 'gravitational lensing'. By this process the gravitational field of an extremely massive body - in this case, a cluster of galaxies - warps the surrounding space. The light emitted from an object - in this case, a quasar - travels amplified and bended, and multiple images of the light source may be seen, each taking a different path through the warped space. Eventhough other multiply lensed quasars have been seen before, this is the only case so far in which multiple quasar images are produced by an entire galaxy cluster acting as a gravitational lens. The galaxy cluster creating the lens is known as SDSS J1004+4112 and was discovered as part of the Sloan Digital Sky Survey. It is one of the more distant clusters known (seven thousand million light-years), and the image we observe today was 'projected' when the Universe was half of its present age. The cluster also creates a cobweb of images of other distant galaxies gravitationally lensed into arcs......... Posted by: Brooke Permalink Source Cobbles in Troughs
Cobbles appearing on trough floors between wind-blown ripples. Image credit: NASA/JPL.
This view, obtained by Opportunity's panoramic camera on the rover's 802nd Martian day (sol) of exploration (April 27, 2006), is a mosaic spanning about 30 degrees. It shows a field of cobbles nestled among wind-driven ripples that are about 20 centimeters (8 inches) high. The origin of cobble fields like this one is unknown. The cobbles may be a lag of coarser material left behind from one or more soil deposits whose finer particles have blown away. The cobbles may be eroded fragments of meteoritic material, secondary ejecta of Mars rock thrown here from craters elsewhere on the surface, weathering remnants of locally-derived bedrock, or a mixture of these. Researchers will use the panoramic camera's multiple filters to study the rock types, variability and origins of the cobbles. This is an approximately true-color rendering that combines separate images taken through the panoramic camera's 753-nanometer, 535-nanometer and 432-nanometer filters......... Posted by: Brooke Permalink Source |
||
| Net World Directory: Navigation |