March 3, 2006, 6:49 AM CT
Interiors Of Giant Icy Moons
Everyday ice used to chill that glass of lemonade has helped scientists better understand the internal structure of icy moons in the far reaches of the solar system.
A research team has demonstrated a new kind of "creep" or flow in a high-pressure form of ice by creating in a laboratory the conditions of pressure, temperature, stress, and grain size that mimic those in the deep interiors of large icy moons.
High-pressure phases of ice are major components of the giant icy moons of the outer solar system: Jupiter's Ganymede and Callisto, Saturn's Titan, and Neptune's Triton. Triton is roughly the size of our own moon; the other three giants are about 1.5 times larger in diameter. Accepted theory says that most of the icy moons condensed as "dirty snow balls" from the dust cloud around the sun (the solar nebula) about 4.5 billion years ago. The moons were warmed internally by this accretionary process and by radioactive decay of their rocky fraction.
The convective flow (much like the swirls in a hot cup of coffee) of ice in the interiors of the icy moons controlled their subsequent evolution and present-day structure. The weaker the ice, the more efficient the convection, and the cooler the interiors. Conversely, the stronger the ice, the warmer the interiors and the greater the possibility of something like a liquid internal ocean appearing.........
Posted by: Edwin Permalink
March 2, 2006, 10:59 PM CT
Ausonia Mensa remnant massif
These images, taken by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express spacecraft, show the Ausonia Mensa massif on Mars.
The HRSC obtained these images during orbit 506 with a ground resolution of approximately 37.6 metres per pixel. The scenes show the region of Hesperia Planum, containing the massif, at approximately 30.3° South and 97.8° East. North is to the right in these images.
March 2, 2006, 10:32 PM CT
vcastro posted a photo:
Comet C/2006A1 (Pojmanski) seen from Mt Laguna predawn 02 MAR 2006. The comet is receding, however it is also rising and becoming well-placed for Northern Hemisphere observers. Canon 20D, 400mm f/2.8, 30sec@f/2.8 @ISO 800.
March 2, 2006, 10:18 PM CT
Cepheids Live in Cocoons
Thu, 02 Mar 2006 - The European Southern Observatory's Very Large Telescope Interferometer has uncovered three Cepheid variable stars surrounded by a cocoon of hot gas. Cepheids are known to pulse in brightness at a regular rate, and used by astronomers to calculate relatively nearby distances. As a Cepheid pulses, the velocity of its photosphere changes dramatically. It could be that this envelope is stellar material left behind as the star grows and shrinks.
March 2, 2006, 10:13 PM CT
Last night before everything was shrouded in a very dens fog, I got a chance to shoot an image of the Moon with the Zeiss Diascope 85 (500mm f/5), the 32mm Televue Plossl and the Nikon Coolpix 4500.
Click to enlarge
The image is a stack of 9 original images, 1/125s, f/3.7, iso 100, 2272x1704. The image has been processed slightly using Noiseware Professional (noise reduction and unsharp masking) and histogram adjustment. The image was cropped to 800x600 (approx.)
February 28, 2006, 11:12 PM CT
What Caused "Man In The Moon"
Ohio State University planetary researchers have found the remains of ancient lunar impacts that may have helped create the surface feature usually called the "man in the moon".
Their study suggests that a large object hit the far side of the moon and sent a shock wave through the moon's core and all the way to the Earth-facing side. The crust recoiled -- and the moon bears the scars from that encounter even today.
The finding holds implications for lunar prospecting, and may solve a mystery about how past impacts on Earth affect it's geology today.
The early Apollo missions revealed that the moon isn't perfectly spherical. Its surface is warped in two spots; an earth-facing bulge on the near side is complemented by a large depression on the Moon's far side. Researchers have long wondered whether these surface features were caused by Earth's gravity tugging on the moon early in its existence, when its surface was still molten and malleable.
As per Laramie Potts and Ralph von Frese, a postdoctoral researcher and professor of geological sciences respectively at Ohio State , these features are instead remnants from ancient impacts.
Potts and von Frese came to this conclusion after they used gravity fluctuations measured by NASA's Clementine and Lunar Prospector satellites to map the moon's interior. They reported the results in a recent issue of the journal Physics of the Earth and Planetary Interiors.........
Posted by: Edwin Permalink Source
February 27, 2006, 9:56 PM CT
Oldest, Most Distant Type 1A Supernova
An exploding star dubbed SN 1997ff, caught once on purpose and twice by accident by NASA's Hubble Space Telescope, is the oldest and most distant Type Ia supernova ever seen, as per a recent analysis by the Department of Energy's National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory.
Berkeley Lab astrophysicist Peter Nugent, a member of the team led by Adam Riess at the Space Telescope Science Institute that studied the distant supernova, used an IBM SP supercomputer to perform the analysis at NERSC, the world's largest unclassified supercomputing center. Nugent says that the serendipitous discovery of the more than 11-billion year old supernova is important for several reasons.
"This supernova is consistent with the cosmological model of an accelerating universe, a universe mostly filled with dark energy," Nugent says. "It argues against the notion that observations of distant Type Ia supernovae may be systematically distorted by intervening gray dust or the chemical evolution of the universe".
Moreover, says Nugent, "the supernova is so ancient that it allows us to glimpse an era when matter in the universe was still relatively dense and expansion was still slowing under the influence of gravity. More recently the dark energy has begun to predominate and expansion has started to speed up".........
Posted by: Edwin Permalink
February 27, 2006, 9:49 PM CT
The Stellar Route To Understanding Dark Energy
The final installment of a series reporting on the Supernova Workshop sponsored by SNAP, the SuperNova/Acceleration Probe collaboration, to investigate the best ways to study dark energy with exploding stars.
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: Edwin Permalink
February 26, 2006, 9:11 PM CT
Pluto's new moons likely born with Charon; Pluto may even have rings
In a paper published Feb. 22, 2006, in Nature, a team of U.S. scientists led by Dr. S. Alan Stern of Southwest Research Institute (SwRI), concludes that two newly discovered small moons of Pluto were very likely born in the same giant impact that gave birth to Pluto's much larger moon, Charon.
The team also argues that other, large binary Kuiper Belt Objects (KBOs) may also frequently harbor small moons, and that the small moons orbiting Pluto may generate debris rings around Pluto.
February 22, 2006, 11:22 PM CT
Image Credits: ESA and JAXA
On 21 February, at 22:28 Central European Time, (22 February, 06:28 local time), a Japanese M-V rocket blasted off from the Uchinoura Space Centre, in the Kagoshima district of Japan, carrying the new infrared satellite into space.
In about two weeks' time, ASTRO-F will be in polar orbit around the Earth at an altitude of 745 kilometres. From there, after two months of system check-outs and performance verification, it will survey the whole sky in about half a year, with much better sensitivity, spatial resolution and wider wavelength coverage than its only infrared surveyor predecessor, the Anglo-Dutch-US IRAS satellite (1983).
The all-sky survey will be followed by a ten-month phase during which thousands of selected astronomical targets will be observed in detail. This will enable researchers to look at these individual objects for a longer time, and thus with increased sensitivity, to conduct their spectral analysis.
This second phase will end with the depletion of the liquid helium needed to cool down the spacecraft telescope and its instruments to only a few degrees above absolute zero. ASTRO-F will then start its third operations phase and continue to make observations of selected celestial targets with its infrared camera only, in a few specific infrared wavelengths.........
Posted by: Edwin Permalink Source
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