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The Stellar Route To Understanding Dark Energy
Supernova cosmology was founded on measurements of distant Type Ia supernovae, and high-z searches for distant supernovae have continued to multiply, using both ground-based telescopes and the Hubble Space Telescope. (Z stands for redshift.). All these searches share the goal of narrowing constraints on possible theories of dark energy by narrowing the allowable values of w, the dark energy "equation of state," the ratio between its pressure and energy density. At the Supernova Workshop Isobel Hook reported, by conference call from England, on a recent report from the Supernova Cosmology Project. After performing several comparisons of high-z and low-z supernovae in a group of 14 Type Ia's, the authors concluded that there are no significant differences among them - or, stated more conservatively, that "there is a sample of high-z Ia's whose properties match those of low-z Ia's." Adam Riess of the Space Telescope Science Institute described the Hubble Space Telescope program named PANS (which stands for Probing Acceleration Now with Supernovae). This search for "higher-z" supernovae seeks the most distant of them all - those from a time when the expansion of the young universe was still slowing, its matter so densely packed that mutual gravitational attraction was strong enough to overcome the negative pressure of dark energy......... Posted by: Brooke Permalink Life Leaves Subtle Signature
Photo Credit: UC-Berkeley
"The meandering stream channels, deltas and alluvial fans of Mars are all familiar to us here," said William Dietrich, a geologist at the University of California at Berkeley. "But we're looking at Mars from a distance. Up close and personal, the view of Earth is a very different one. "Can we tell from topography alone that life pervades Earth?" wondered Dietrich and colleagues. They found, to their surprise, no overt signature of life in Earth's landforms, but a more muted signature does exist. The main topographical difference between an Earth teeming with life and one with no life, Dietrich concludes, is that life likely creates more of the rounded hills typical of Earth's vegetated areas, and fewer sharp, rocky ridges. "It turns out that life creates a more subtle effect on the land," said Richard Lane, program director in the National Science Foundation's (NSF) Division of Earth Sciences. "The absence of life likely would lead to a planet with sharp hill slopes of exposed bedrock, which is not what Earth looks like". Everywhere you look, "life is causing sediment to move downhill," Dietrich said. "Tree roots, gophers and wombats all dig into the soil and raise it, tearing up the underlying bedrock and turning it into rubble that tumbles downhill and leaves behind more rolling hills"......... Posted by: Ashley Permalink February 26, 2006, 9:13 PM CT Venus Express Ground Observing Project  The Venus Express Ground Observing Project (VEXGOP) is an opportunity to contribute scientifically useful images and data to compliment the Venus Express (VEX) spacecraft observations of Venus. The project will focus on utilising the capabilities of advanced amateurs to obtain images of the atmosphere of Venus; specifically filtered monochrome images obtained with CCD based cameras in the 350nm to 1000nm (near ultraviolet, visible and near infrared range).
Radioactivity from the Inner Part of Our Galaxy
Radioactive decay of unstable isotopes leads to emission of gamma rays with a characteristic energy (coloured) being determined by properties of the atomic nucleus. ESA's INTEGRAL satellite observatory has been measuring such gamma rays since October 2002. Radioactive isotopes are by-products of nuclear fusion reactions, which produce new atomic nuclei in stellar interiors and in supernovae. In the gamma ray light of 26Al isotopes, which decay after about a million years to magnesium, one sees the radioactive glow of regions of the Galaxy with recent production of new nuclei. Visible light, on the other hand, often cannot reach us from stars in those regions, due to occulting interstellar gas clouds.
Image credit: Max Planck Institute for Extraterrestrial Physics
We are familiar with radioactive isotopes from medical radiology tests and therapys. Astrophysicists use penetrating gamma rays emitted during radioactive decay to obtain direct messages from cosmic nuclear fusion reactions, through special telescopes operated in near-Earth space. Gamma-rays from decaying 26Al were detected in 1978, and because of its known half life of 720, 000 years, this provided direct proof of currently-ongoing nucleosynthesis. Supernova 1987 in the Large Magellanic Cloud galaxy was then observed through short-lived radioactive gamma rays. This led researchers to think that these nuclei had been produced within this supernova event......... Posted by: Brooke Permalink Source New Infrared Sky Surveyor
Orbiting the Earth, ASTRO-F (to be renamed Akari (light) now that it is in orbit) will make an unprecedented study of the sky in infrared light, to reveal the distant phenomena hidden from our eyes that tell the story of the formation and evolution processes taking place in the universe. Prof. David Southwood, ESA's Director of Science, said: "The successful launch of ASTRO-F (Akari) is a big step. A decade ago, our Infrared Space Observatory (ISO) opened up this field of astronomy, and the Japanese took part then. It is wonderful to be cooperating again with Japan in this discipline". "Our involvement with the Japanese in this programme responds to our long-term commitment in infrared astronomy, whose potential for discovery is huge. We are now off and rolling with ASTRO-F/Akari, but we are also working extremely hard towards the launch of the next-generation infrared telescope, ESA's Herschel spacecraft, which will go up in the next two years," he continued. "This will still not be the end of the story. Infrared astronomy is also a fundamental part of the future vision for ESA's space research, as outlined in the 'Cosmic Vision 2015-2025' programme. The truth is, subjects such as the formation of stars and exoplanets, or the evolution of the early universe, are themes at the very core of our programme."........ Posted by: Brooke Permalink Source Shadow on the surface of Mars
The HRSC obtained these unique images during orbit 2345 on 10 November 2005. These observations would not have been possible without the close co-operation between the camera team at the Institute of Planetary Research at DLR and the ESA teams, in particular the mission engineers at ESA's European Space Operations Centre (ESOC) in Darmstadt, Gera number of. They confirm the model of the moon's orbit around Mars, as it was determined earlier in 2004 also on the basis of HRSC images. They also show that with accurate planning even moving objects can be captured exactly at their predicted position. The basis for such observations is the accurate knowledge of the spacecraft position in its orbit as well as of the targeted location on Mars to within a few hundred metres. Phobos is the larger of the two Martian moons, 27 kilometres by 22 kilometres in size, and travels around Mars in an almost circular orbit at an altitude of about 6000 kilometres. Phobos takes slightly more than 7.5 hours to complete a full revolution around the planet. When it is between the Sun and Mars, Phobos casts a small and diffuse shadow onto the Martian surface. To an observer on Mars, this would appear as a very quick eclipse of the Sun. This is similar to an eclipse on Earth, when the Moon covers the solar disk but much slower......... Posted by: Brooke Permalink Source Indentation In Spacetime From A Spinning Black Hole
Artist impression of the black hole binary system GRO J1655-40 (Rob Hynes)
Image courtesy of University of Michigan
The finding may help researchers measure a black hole's mass and how it spins, two long-sought measurements, by virtue of the extent of this indentation. Using NASA's Rossi X-ray Timing Explorer, the team of researchers saw identical patterns in the X-ray light emitted near the black hole over nine years, as captured in archived data from 1996 and in a new, unprecedented 550-hour observation from 2005. Black hole regions are notoriously chaotic, generating light at a range of frequencies. Similarities seen nine years apart imply something fundamental is producing a pair of observed frequencies, namely the warping of space and time predicted by Einstein but rarely seen in such detail. Jeroen Homan of MIT's Kavli Institute and his team, which included Jon Miller of U-M, Rudy Wijnands of Amsterdam University and Walter Lewin of MIT, presented the result at the American Astronomical Society meeting in Washington this week. "The fact that we found the exact same frequency of X-ray oscillations nine years later is likely no coincidence," Homan said. "The black hole is still singing the same tune. The oscillations are created by a groove hammered into spacetime by the black hole. This phenomenon has been suspected for a while, but now we have good evidence to support it."........ Posted by: Brooke Permalink Source Neutron star that spins toward intergalactic space
Jason Koski/University Photography
Professor of astronomy Jim Cordes stands beside an image of a galaxy similar to the Milky Way in Cornell's Space Sciences Building. Copyright Cornell University
Using the Very Long Baseline Array (VLBA), 10 radio telescopes spanning 5,000 miles from Hawaii to the U.S. Virgin Islands, James Cordes, professor of astronomy at Cornell University, his former student Shami Chatterjee, now of the Harvard-Smithsonian Center for Astrophysics, and his colleagues studied the pulsar (a fast-spinning neutron star) B1508+55, about 7,700 light years from Earth. With the ultra-sharp radio vision of the continentwide VLBA, they precisely measured both the distance and the speed of the pulsar. The team then plotted the star's motion backward to a birthplace among groups of giant stars in the constellation Cygnus, which contains stars so massive they inevitably explode as supernovae. Commenting on the research, which was published last fall in Astrophysical Journal Letters, Chatterjee said, "We know that supernova explosions can give a kick to the resulting neutron star, but the tremendous speed of this object pushes the limits of our current understanding. This discovery is very difficult for the latest models to explain." Chatterjee is also a Jansky fellow at the National Radio Astronomy Observatory (NRAO)......... Posted by: Brooke Permalink Source Perspective View Of Phlegethon Catena
The HRSC obtained this images during orbit 1217 with a ground resolution of approximately 11.9 metres per pixel. The scenes show the region of Phlegethon Catena, centred at approximately 33.9 degree South and 253.1 degree East. Located south-east of the Alba Patera volcano, Phlegethon Catena is a region exhibiting a high density of tectonic grabens, which are blocks of terrain that have dropped relative to their surroundings as a result of a geological extension of the crust. It is unclear what process is responsible for the chain of depressions. One possibility is the collapse of the surface due to the removal of subsurface materials, while other suggestions include that tension cracks may have formed in the subsurface and caused subsequent collapse. The colour scenes have been derived from the three HRSC-colour channels and the nadir channel. The perspective views have been calculated from the digital terrain model derived from the stereo channels. The 3D anaglyph image was calculated from the nadir and one stereo channel. Image resolution has been decreased for use on the internet......... Posted by: Brooke Permalink Source How Do You Steal A Million Stars?
"In the solar neighbourhood and in most stellar clusters, the least massive stars are the most common, and by far", said Guido De Marchi (ESA), lead author of the study. "Our observations with ESO's VLT show this is not the case for Messier 12." The team, which also includes Luigi Pulone and Francesco Paresce (INAF, Italy), measured the brightness and colours of more than 16,000 stars within the globular cluster Messier 12 with the FORS1 multi-mode instrument attached to one of the Unit Telescopes of ESO's VLT at Cerro Paranal (Chile). The astronomers could study stars that are 40 million times fainter than what the unaided eye can see (magnitude 25). Located at a distance of 23,000 light years in the constellation Ophiuchus (The Serpent-holder), Messier 12 got its name by being the 12th entry in the catalogue of nebulous objects compiled in 1774 by French astronomer and comet chaser Charles Messier. It is also known to astronomers as NGC 6218 and contains about 200,000 stars, most of them having a mass between 20 and 80 percent of the mass of the Sun......... Posted by: Brooke Permalink |
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