SATURN PHOTO-OP: Something is about to happen on Saturn that is so pretty, even Hubble will pause to take a look. Backyard astronomers can see it, too. Four of Saturn's moons will transit Saturn and cast their shadows on the planet's cloudtops at the same time: full story. 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. Comet Lulin Photo Gallery [Comet Hunter Telescope] [Sky maps: Feb. 18, 19, 20] SATELLITE DEBRIS: More than a week has passed since the Feb. 10th collision of Iridium 33 and Kosmos 2251 over northern Siberia, and the orbits of some of the fragments have now been measured by US Strategic Command. Orbital elements are available for 8 pieces of debris from Iridium 33 and 18 pieces from Kosmos 2251. Satellite observer Daniel Deak has plotted those orbits on a 3D map of Earth for readers of Spaceweather.com. Click on the image to view the distribution of Iridium debris on Feb. 18th: A similar map highlights the Kosmos debris, and a polar view is available, too. In the maps, hollow circles denote primary fragments still being tracked with the same catalogue number as the original satellite. "We can say it is what remains of the satellite after the collision," explains Deak. Solid circles denote lesser fragments; they are scattered almost all the way around Earth. A comparison of Kosmos vs. Iridium maps shows that Kosmos debris is scattered more widely than Iridium debris in orbital phase, eccentricity and inclination. For some reason, Kosmos fragments seem to have been ejected from the crash with a greater velocity than Iridium counterparts. This is just the beginning. More fragments, perhaps hundreds of them, will be catalogued in the days and weeks ahead. As they are added to the map, new information about the crash and its aftermath will naturally emerge. Stay tuned! February 2009 Aurora Gallery [Previous Februaries: 2008, 2007, 2006, 2004, 2003, 2002] Explore the Sunspot Cycle |