February 17, 2005Testing the order of cosmic evolution
Astronomers have found evidence concerning the evolution of cosmic structure that may turn the favored theory upside down. Literally.
Scientists from an international collaboration using the Subaru/XMM-Newton Deep Survey
(SXDS) have found galaxy clusters that formed a billion years after the Big Bang.
The accepted theory of structure formation — the "bottom-up" model — implies the first structures to form were clumps of matter smaller than galaxies. These structures congregated to form galaxies, then galaxy clusters, and finally, superclusters. The most important aspect of the bottom-up model is the hierarchy of evolution: small to big.
By saying clusters formed far earlier than believed, the SXDS astronomers contradict this model. The astronomers do, however, acknowledge that this finding does not mean cosmologists should throw out all earlier theories and start from scratch. "The real challenge is in understanding how well the distribution of visible matter such as galaxies correlates with the distribution of mass in general," says Masami Ouchi, a group member currently at the Space Telescope Science Institute in Baltimore.
SXDS is currently gathering data in wavelengths from X rays to radio waves. When the survey is complete, a few years from now, scientists hope to be able to determine the details of cosmic evolution. The astronomers' research appeared in the February 10, 2005 issue of The Astrophysical Journal
. — Liz KruesiShuttle: one more hurdle passed
The shuttle Discovery is one step closer to launch, still scheduled for sometime between May 14 and June 3, 2005. According to the independent advisory task group chaired by former astronauts Thomas Stafford and Richard Covey, NASA has successfully "closed" (fulfilled) another of the 15 recommendations made by the Columbia Accident Investigation Board (CAIB).
CAIB recommendation 3.3-1 told NASA to develop ways to check the integrity of the reinforced carbon-carbon (RCC) areas of the wings and tail during the turnaround time between shuttle flights. The Stafford-Covey panel had "conditionally closed" this recommendation in April 2004. In a teleconference among members February 17, the panel accepted NASA's evidence that it can verify the RCC surfaces are safe using X rays, heat imaging, and airflow tests.
Of the eight CAIB recommendations left outstanding, one has been conditionally closed and seven still remain open. The Stafford-Covey group will meet again March 29 to 31 to determine the status of the remaining recommendations. In a teleconference with journalists following the panel's meeting, cochair Richard Covey acknowledged that NASA still has a lot of work to do, but he foresaw "no showstoppers." — Robert Burnham