AURORA WATCH: Arctic sky watchers should be alert for Northern Lights tonight. A solar wind stream is heading for Earth, and NOAA forecasters estimate a 30% chance of high-latitude geomagnetic activity when it arrives sometime during the next 24 hours: gallery. GRAND CENTRAL STATION: On Feb. 17th and 18th, many observers of Comet Lulin saw something unexpected. In addition to the comet, "I kept getting satellite trails in my images," reports John Cordiale of Queensbury, New York. "It was like Grand Central Station. Multiple groupings of satellites traveled through my images for hours." He photographed the activity using a 2.5-inch (65mm) refractor: "It made me wonder if I was seeing debris from the recent double satellite collision," says Cordiale. It certainly looked like flying debris (see this animation from Jesus Pelaez of Padilla de Arriba, Spain). But no, what Cordiale, Pelaez and others saw was actually a band of intact geostationary satellites. Geostationary satellites orbit Earth twenty-two thousand miles above the equator, always keeping station above a single point on the ground. While geosats are stationary with respect to Earth's surface, they move with respect to the stars. Viewed through the eyepiece of a star-tracking telescope, the stars are motionless while the "stationary" satellites streak through the field of view like so much debris. Strange but true. From mid-Northern latitudes, geostationary satellites occupy a band of declinations between approximately -5 and -7 degrees. By happenstance, Comet Lulin passed through that band on Feb. 17th and 18th, setting the stage for an unexpected show. "I had never seen anything like it!" says Cordiale. UPDATED: Comet Lulin Photo Gallery [Comet Hunter Telescope] [Sky maps: Feb. 18, 19, 20] SATELLITE DEBRIS UPDATE: US Strategic Command has identified a new batch of fragments from the Feb. 10th satellite collision over northern Siberia. "The count is now at 49 pieces for Iridium 33 and 85 for Kosmos 2251," says Canadian satellite tracker Daniel Deak, who has prepared some 3D maps of the debris for readers of spaceweather.com. Click on the image to view a snapshot of Iridium fragments on Feb 20th: A similar map traces the Kosmos debris. Observations: Both satellites are now smeared all the way around Earth; the original orbits are completely populated with fragments. Furthermore, for reasons not fully understood, Kosmos is more widely scattered than Iridium. "The Kosmos debris ranges in altitude from 260 to 1450 km, so some of the pieces now reach lower than the 350-km orbit of the ISS," points out Deak. "For the Iridium debris, the fragments are confined to orbits between 687 and 1127 km." This doesn't mean the ISS is in immediate peril. Most of the Kosmos scatter occurs over Antarctic latitudes. For comparison, the ISS stays within 51.6 degrees of Earth's equator, so the dangers are slight. The situation could change, however, as more fragments are identified and their spread increases. Stay tuned for updates. A complete set of debris maps: #1, #2, #3, #4, #5 February 2009 Aurora Gallery [Previous Februaries: 2008, 2007, 2006, 2004, 2003, 2002] Explore the Sunspot Cycle |