he interplanetary space probe Deep Impact is set to blast a hole in Comet 9P/Tempel 1 July 4. In excavating a stadium-size crater, the probe will allow planetary scientists to analyze the composition of frozen material dating back to the solar system's formation. No one knows what effects the impact will have on the comet's appearance, but astronomers think there's a reasonable chance backyard observers far from city lights will see a change in the comet's dusty halo in the early morning of the 4th. Use the chart on page 61 to locate the comet, and log onto Astronomy.com
for observing tips and tricks.