Deep Impact closes in on comet target

Extensive Astronomy magazine coverage of Deep Impact
***Both of these articles and supplemental graphics are AVAILABLE FOR DOWNLOAD.***

Check out Astronomy magazine’s June 2005 issue for “Fireworks on the Fourth.” This 3-page article previews the much-anticipated collision and provides a map of the comet’s location in the sky. In the 2005 edition of Astronomy magazine’s annual Explore the Universe, you’ll find “Deep Impact delivers a hit.” This 6-page feature includes an illustration of Deep Impact’s collision course with Tempel 1 and provides a comprehensive overview of the historic mission. Be sure to follow Astronomy and Astronomy.com to keep abreast of the latest findings from the Deep Impact mission.

WAUKESHA, WI &#151 In the early morning hours of July 4, a projectile from NASA’s Deep Impact spacecraft will smash into Comet Tempel 1. Professional and amateur astronomers around the world will keep their eyes glued on the comet, seeking to learn more about this relic from the ancient past &#151 and hoping to view some celestial fireworks.

Comets like Tempel 1 consist of ice and dust &#151 they’re “dirty snowballs,” as American astronomer Fred Whipple once famously described them. They date back to the solar system’s origin some 4.5 billion years ago and have spent most of their lives in the deep freeze at the solar system’s edge. This makes them time capsules that hold clues as to how the solar system formed and evolved. Yet, most of these clues lie buried beneath a veneer of material altered by exposure to space and sunlight.

Enter Deep Impact. NASA launched the spacecraft January 12, 2005, putting it on a collision course with Tempel 1. Deep Impact actually consists of two spacecraft: an impactor and a larger flyby spacecraft. The impactor will slam into the comet’s nucleus, while the flyby craft will study the crater using a suite of instruments. The collision is expected to expose fresh comet material. The two spacecraft will separate about 24 hours before impact &#151 impact is scheduled for 1:52 a.m. EDT July 4 (10:52 p.m. PDT July 3).

The solid copper impactor weighs 816 pounds and will travel 23,000 mph when it hits Tempel 1, creating a blast equivalent to 4.8 tons of TNT. Astronomers speculate the crater could be as small as a house or as big as a football stadium, and anywhere from 2 to 14 stories deep.

Sunlight reflecting off material expelled by the blast should cause the comet to brighten dramatically. Although it likely will remain below naked-eye visibility, the comet will come within easy range of backyard observers using small telescopes. Potentially, freshly excavated ice will convert to gas in sunlight, creating a jet of material that could keep the comet brighter than normal for weeks or even months. In addition to observations made by the flyby spacecraft, professional astronomers will be viewing the impact and its aftermath with many of Earth’s biggest telescopes, as well as with the Hubble Space Telescope.

Fast facts about Deep Impact and Comet Tempel 1: