July 18, 2007, 7:29 PM CT

An Ice Machine in the Ultimate Deep Freeze

Frigid geysers spewing material up through cracks in the crust of Pluto's companion Charon and recoating parts of its surface in ice crystals could be making this distant world into the equivalent of an outer solar system ice machine.

Evidence for these ice deposits comes from high-resolution spectra obtained using the Gemini Observatory's Adaptive Optics system, ALTAIR coupled with the near-infrared instrument NIRI. The observations, made with the Frederick C. Gillett Gemini North telescope on Hawaii's Mauna Kea, show the fingerprints of ammonia hydrates and water crystals spread in patches across Charon, and have been described as the best evidence yet for the existence of these compounds on worlds such as Charon. The observations suggest that liquid water mixed with ammonia from deep within Charon is pushing out to the ultra-cold surface. This action could be occurring on timescales as short as a few hours or days, and at levels that would recoat Charon to a depth of one millimeter every 100,000 years. This discovery could have profound implications for other similar-type worlds in the Kuiper Belt, which is the region of the solar system that extends out beyond the orbit of Neptune and contains many small bodies, the largest of which include Pluto and Charon.

"There are many mechanisms that could explain the presence of crystalline water ice on the surface of Charon," said Jason Cook, the PhD student at Arizona State University who led the team of planetary researchers studying the surface of Charon. "Our spectra point consistently to cryovolcanism, which brings liquid water to the surface, where it freezes into ice crystals. That implies that Charon's interior possesses liquid water."........ Posted by: Sean      Read more         Source

July 12, 2007, 10:56 PM CT

Images from AKARI

AKARI's Far Infrared Surveyor (FIS) instrument also observed the Milky Way and the Orion region. In this image, two views at visual light (left) and infrared light (right) are juxtaposed, both covering a region of about 30x40 square degrees. AKARI's view is taken at 140 micrometres. For the first time ever, AKARI provided coverage of the Orion region at infrared wavelengths longer than 100 micrometres at such fine resolution.

The right side of the image covers the constellation Orion while the left side shows the Monoceros. The Galactic Plane is located from the top to bottom in the left side of the image. Cold dust in the Galactic Plane appears as diffuse radiation over the entire image.

Credits: Hideo Fukushima, National Astronomical Observatory Japan (left); JAXA (right)......... Posted by: Sean      Read more         Source

July 12, 2007, 10:54 PM CT

False-colour Composite

This false-colour composite was obtained by AKARI's Far Infrared Surveyor (FIS) instrument at 90 and 140 micrometres. It shows star-forming regions in the constellation Cygnus, one of the brightest regions in the Milky Way. The image covers 7.6 x 10.0 square degrees.

This region is in a direction along the so-called 'Orion arm', one of the spiral arms of our Galaxy. A number of objects at distances of three thousand to ten thousand light years are projected on this small region. The Galactic plane appears from the top-left to bottom-right......... Posted by: Sean      Read more         Source

July 12, 2007, 5:40 AM CT

Giant Outer Extrasolar Planets Are Rare

Astronomers who used powerful telescopes in Arizona and Chile in a survey for planets around nearby stars have discovered that extrasolar planets more massive than Jupiter are extremely rare in other outer solar systems.

University of Arizona astronomers and their collaborators from the European Southern Observatory, the Max Planck Institute for Astronomy in Heidelberg, Italy's Arcetri Observatory, the W.M. Keck Observatory and the Harvard-Smithsonian Center for Astrophysics just concluded a benchmark three-year survey using direct detection techniques sensitive to planets farther from their stars. The survey looked at 54 young, nearby stars that were among the best candidates for having detectable giant Jupiter-like planets at distances beyond five astronomical units (AU), or the distance between Jupiter and the sun. One AU is the distance between Earth and the sun.

Since 1995, astronomers have found more than 230 "super Jupiters" orbiting very close to their parent stars using the radial velocity method. This indirect planet-detecting technique measures the slight back-and-forth motion of the star as it is tugged by an unseen planet's gravity. Researchers have written more than 2,000 scholarly papers about these giant Jupiter-like planets within a few Earth-to-sun distances of their stars......... Posted by: Sean      Read more         Source

July 10, 2007, 5:32 AM CT

Characterizing Density Wave Features

In a paper published in The Astronomical Journal (133:2584-2606, June 2007) Dr. Xiaolei Zhang, of the Naval Research Laboratory, and Dr. Ronald J. Buta, of the University of Alabama, report that they have developed an accurate and widely-applicable method for characterizing density wave features in galaxies. These density waves appear as high-density regions in galaxies in the forms of spirals, bars, and rings. Orbiting stars and gas stream in and out of these features much like in a traffic jam. Density wave in galaxies has been an active area of study among astronomers and mathematicians since the early part of 1960s. A popular account of the history of the development of density wave theory can be found in the September 2002 issue of Sky and Telescope magazine.

The density waves in the different regions of a galaxy's disk often appear as intricately nested segments of patterns (bars within bars, or bars within spirals, see the figure at the end of this article), each segment rotating rigidly with a fixed pattern speed. Using near-infrared light as a mass-density tracer, the new method allows the pattern speeds of the different nested density wave patterns to be determined empirically by calculating the gravitational potential field produced by these density patterns......... Posted by: Sean      Read more         Source

July 4, 2007, 5:02 AM CT

Stellar fireworks through Hubble's eyes

Nearly 12.5 million light-years away, in the dwarf galaxy NGC 4449, stellar fireworks on display have been captured by the Hubble Space Telescope.

NGC 4449 belongs to a group of galaxies in the constellation Canes Venatici, 'the Hunting Dogs'. Astronomers believe that NGC 4449's episode of star formation has been influenced by interactions with several of its neighbours. It is likely that the current widespread starburst was triggered by interaction or merger with a smaller companion.

The NASA/ESA Hubble Space Telescope's Advanced Camera for Surveys observed NGC 4449 in the visible (blue and green), infrared, and hydrogen-alpha regions of the spectrum.

Hundreds of thousands of vibrant blue and red stars are visible in this new image. Hot bluish white clusters of massive stars are scattered throughout the galaxy, interspersed with numerous dustier reddish regions where star formation is taking place. Massive, dark clouds of gas and dust are silhouetted against starlight.

NGC 4449 has been forming stars for thousands of millions of years, but is currently experiencing star formation at a much higher rate than in the past. This unusual explosive and intense activity qualifies as a starburst, meaning that at the current rate, the gas that feeds stellar production would run out in about a thousand million years......... Posted by: Sean      Read more         Source

July 3, 2007, 5:15 AM CT

Tectonic signatures at Aeolis Mensae

The High Resolution Stereo Camera (HRSC) on board Mars Express has provided snapshots of the Aeolis Mensae region. This area, well known for its wind-eroded features, lies on a tectonic transition zone, characterised by incised valleys and unexplained linear features.

Illuminated by the Sun from the west (right side in the image), the pictures are of a ground resolution of approximately 13 metres per pixel. The region, imaged on 26 and 29 March 2007, during Mars Express orbits 4136 and 4247, is located at approximately 6 degree South and 145 degree East.

The morphology of the terrain, which lies close to the volcanic region of Elysium, is characterised by an extensive transition zone or the so-called 'global crustal dichotomy boundary' which separates the southern highlands and northern lowlands. It exhibits clod-shaped or lumpy relief separated by valleys and graben structures, or elongated, trench-like erosional features.

Aeolis Mensae is located at the border between the northern plains and the southern highlands, indicated by the transition zone. The area shown in the image mosaic is part of the southern highlands and the transition zone to the north. Between the highlands and the plains there is a large average difference in elevation, of about 3000 metres. The origin of this dichotomy is currently a subject of discussion......... Posted by: Sean      Read more         Source

July 3, 2007, 5:06 AM CT

What happened before the Big Bang?

New discoveries about another universe whose collapse appears to have given birth to the one we live in today will be announced in the early on-line edition of the journal Nature Physics on 1 July 2007 and would be reported in the August 2007 issue of the journal's print edition. "My paper introduces a new mathematical model that we can use to derive new details about the properties of a quantum state as it travels through the Big Bounce, which replaces the classical idea of a Big Bang as the beginning of our universe," said Martin Bojowald, assistant professor of physics at Penn State. Bojowald's research also suggests that, eventhough it is possible to learn about a number of properties of the earlier universe, we always will be uncertain about some of these properties because his calculations reveal a "cosmic forgetfulness" that results from the extreme quantum forces during the Big Bounce.

The idea that the universe erupted with a Big Bang explosion has been a big barrier in scientific attempts to understand the origin of our expanding universe, eventhough the Big Bang long has been considered by physicists to be the best model. As described by Einstein's Theory of General Relativity, the origin of the Big Bang is a mathematically nonsensical state -- a "singularity" of zero volume that nevertheless contained infinite density and infinitely large energy. Now, however, Bojowald and other physicists at Penn State are exploring territory unknown even to Einstein -- the time before the Big Bang -- using a mathematical time machine called Loop Quantum Gravity. This theory, which combines Einstein's Theory of General Relativity with equations of quantum physics that did not exist in Einstein's day, is the first mathematical description to systematically establish the existence of the Big Bounce and to deduce properties of the earlier universe from which our own may have sprung. For scientists, the Big Bounce opens a crack in the barrier that was the Big Bang......... Posted by: Sean      Read more         Source

Fri, 29 Jun 2007 11:32:39 GMT

Satellites Discovered ‘Twilight Zone

Scientists seem to be satisfied with all their findings about the clouds and the sun and their mutual links and contributions towards the environment. They are now trying to go a step forward trying to find out, whats happening up there in between the clouds and the sun.

To the surprise of both the researchers in U.S. and Israeli, they have discovered a in the area between clouds and the sun, which are said to be made of particles that are ‘neither wet nor dry’.

The 60 percent of the atmosphere labeled as cloud-free, is actually found to be filled with this twilight zone of in-between particles, as been observed by satellites. Thanks to the scientists from Israel’s Weizmann Institute and NASA’s Goddard Space Flight Center in Greenbelt, Md.

Goddard’s Lorraine Remer in a release said,

With the highly sensitive Earth-observing instruments NASA has used since 2000, we can distinguish aerosols and clouds in greater detail than ever before.But the area around clouds has given us trouble. The instruments detected something there, but it didn’t match our understanding of what a cloud or an aerosol looked like.

Trying to explain the zone, Remer addresses this as a could be transitional zone.

It is perhaps where; the clouds that begin to form die away. It is here the humidity may cause dry particles to absorb water and get bigger.

Though the researchers are yet to go far with their research to confirm on it, the climate scientists have already realized that the twilight zone would surely lead them recalculate their best estimates of how Earth’s atmosphere not only holds, but also reflects solar energy.


Photo: met.utah.edu Posted by: Irani      Read more     Source

June 27, 2007, 7:07 PM CT

Neutron stars join the black hole jet set

NASAs Chandra X-ray Observatory has revealed an X-ray jet blasting away from a neutron star in a binary system. This discovery may help astronomers understand how neutron stars as well as black holes can generate powerful beams of relativistic particles.

The jet was found in Circinus X-1, a system where a neutron star is in orbit around a star several times the mass of the Sun, about 20,000 light years from Earth. A neutron star is an extremely dense remnant of an exploded star consisting of tightly packed neutrons.

A number of jets have been found originating near black holes - both the supermassive and stellar-mass variety - but the Circinus X-1 jet is the first extended X-ray jet linked to a neutron star in a binary system. This detection shows that the unusual properties of black holes - such as presence of an event horizon and the lack of an actual surface - may not be mandatory to form powerful jets.

"Gravity appears to be the key to creating these jets, not some trick of the event horizon," said Sebastian Heinz of the University of Wisconsin at Madison, who led the study.

The discovery of this jet with Chandra also reveals how efficient neutron stars can be as cosmic power factories. Heinz and colleagues estimate that a surprisingly high percentage of the energy available from material falling onto the neutron star is converted into powering the jet......... Posted by: Sean      Read more         Source