Thursday, December 29, 2005

Milky Way's Neighboring Spiral Arm is Closer Than Thought

SpaceRef - Your Space Reference

"The Perseus spiral arm - the nearest spiral arm in the Milky Way outside the Sun's orbit - lies only half as far from Earth as some previous studies had suggested. An international team of astronomers measured a highly accurate distance to the Perseus arm for the first time using a globe-spanning system of radio dishes known as the Very Long Baseline Array (VLBA), which offers the sharpest vision of any telescope in existence. Additional VLBA measurements will help astronomers to determine the true structure of the Milky Way."

"Obtaining accurate distances in astronomy is a difficult challenge. The most reliable method for measuring astronomical distances is called trigonometric parallax, a technique similar to the triangulation used by land surveyors. A trigonometric parallax is determined by observing the change in position of a star relative to a very distant, essentially fixed object like a quasar, as the Earth moves in its orbit around the Sun. Just as a finger held at arm's length appears to shift against the far wall when viewed with one eye or the other, a nearby object will appear to shift position relative to a more distant one. Mathematical calculations then yield the distance to the closer object. The parallax method is powerful but requires exceptional accuracy."

Friday, December 09, 2005

"Energy Dept. Completes Nuke Site Cleanup"

Washington Post

"The Energy Department declared the cleanup of Rocky Flats completed Thursday, the first former nuclear weapons site to be totally remediated."

New Cellular Structures

"Researchers say they've identified tiny structures that may prepare the groundwork for how new cells form and function. These cellular structures, called GW bodies, play an important role in gene regulation (RNA interference), according to a team from the University of Florida, Gainesville."

Tuesday, December 06, 2005

"Rivers on Titan Resemble Those on Earth"

SpaceRef - Your Space Reference

"Recent evidence from the Huygens Probe of the Cassini Mission suggests that Titan, the largest moon orbiting Saturn, is a world where rivers of liquid methane sculpt channels in continents of ice. Surface images even show gravel-sized pieces of water ice that resemble rounded stones lying in a dry riverbed on Earth.

"But with a surface temperature of minus 179 degrees Celsius and an atmospheric pressure 1 1/2 times that of Earth, could fluvial processes on Titan be anything like those on Earth?

" 'The idea that rivers of methane moving chunks of ice on Titan ought to obey the same rules as rivers on Earth is not what you would assume at first,' said Gary Parker, the W. H. Johnson Professor of Geology and a professor of civil and environmental engineering at the University of Illinois at Urbana-Champaign. 'However, if river dynamics are truly understood at a physical level, then relations that provide reasonable results on Earth ought to provide similarly reasonable results on Titan.' "