Deep Impact successfully released its 820-pound impactor this morning at 2:07 EDT (0607 GMT), some 880,000 kilometers from the Tempel 1 comet. The Jet Propulsion Laboratory has also reported that six hours before release of the impactor, the spacecraft performed a successful trajectory correction, using a 30-second burn to change Deep Impact's velocity by about one kilometer per hour. Another burn occurred twelve minutes after impactor release, when the flyby spacecraft began a 14-minute burn designed to move it out of the path of the oncoming comet and place it in the best position to observe the impact. Image: One hundred and seventy-one days into its 172-day journey to comet Tempel 1, NASA's Deep Impact spacecraft successfully released its impactor at 2:07 a.m. Sunday, Eastern Daylight Time. This image of Deep Impact's impactor probe was taken by the mission's mother ship, or flyby spacecraft, after the two separated. Image credit: NASA/JPL-Caltech.

No one knows quite what to expect when the Deep Impact probe slams into comet Tempel 1, but countless amateur astronomers plan to be watching to see if the comet brightens following the collision. And it might, given the amount of material that could be dislodged by the event. A telescope or set of binoculars will probably be required, although dedicated skywatchers can still see the spot in the sky where the big event will occur even without the aid of such equipment. The time of impact is 1:52 EDT (0552 GMT) on the morning of July 4, a time when the comet will be best placed for viewing from the American southwest, although Kelly Beatty, executive editor of SKY & TELESCOPE magazine, is now saying that anyone west of the Mississippi has a good chance of seeing it. From a news release just issued by the magazine, here is where to look: After dark, find Jupiter shining high in the southwest. It's the brightest "star" in that part of the sky (brighter Venus sets in the west-northwest...