Asteroid Population Doubles
April 5, 2002 | Observations made in 1996–97 by the European Space Agency's Infrared Space Observatory show that the asteroid belt contains about twice as many objects as previously thought. The new census involved tallying up the main-belt asteroids spotted in selected locations, then extrapolating those counts to include the entire sky. The result, says Edward Tedesco (TerraSystems), suggests that the main belt (between Mars and Jupiter) contains 1.1 to 1.9 million minor planets at least 1 kilometer across. Previous studies in 1998 and 2001 had estimated the count of 1-km or larger objects at 860,000 and 740,000, respectively.
For more details, read the European Space Agency's press release at http://www.esa.int/export/esaCP/ESAASPF18ZC_index_0.html.
Hubble Ready to Resume Operations
April 5, 2002 | After three weeks of intensive checks and testing, engineers both at NASA's Goddard Space Flight Center and at the Space Telescope Science Institute have declared that the Hubble Space Telescope is ready to resume its mission. The spacecraft's new solar-cell arrays, installed early last month by Columbia's spacewalking astronauts, are delivering 27 percent more electricity than their predecessors. The powerful new Advanced Camera for Surveys, also delivered by Columbia, is now undergoing its final alignment and focusing checks. Astronomers hope to unveil the ACS's first images in about a month.
More details can be found in a press release issued by NASA's Goddard Space Flight Center: http://www.gsfc.nasa.gov/news-release/releases/2002/02-051.htm.
Gamma-Ray Bursts and Supernovae: One More Link
April 4, 2002 | Astronomers have found yet more evidence that gamma-ray bursts are closely associated with supernova explosions of massive stars. James Reeves (University of Leicester, England) and colleagues found hot gas containing magnesium, silicon, sulfur, argon, calcium, and other elements streaming from the source of a gamma-ray burst at a tenth of the speed of light. This is just the kind of mix expected from a Type II supernova. The gamma burst itself is believed to be directed along a narrowly collimated jet of much faster debris coming from right around a newborn black hole in certain supernova cores.
The report appears in today's issue of Nature.