Posted on: Monday, June 27, 2005

Island eyes on heavens for Deep Impact

By Jan TenBruggencate
Advertiser Science Writer

Every telescope on Mauna Kea, two on Haleakala, and a fair proportion of Hawai'i residents' personal telescopes and binoculars will focus Sunday night on an astronomical first: an exploding dust cloud from a comet being hit by a missile.

Space scientists hope that NASA's Deep Impact mission will turn the nearly invisible passing Comet Tempel 1 into a flash of light nearly as bright as the North Star.

The explosion of dust and ice from the comet's interior may be visible to the naked eye, but the astronomy community is engaged in an unprecedented effort to make publicly available its best technology-aided imagery.

"We're pleased that a cosmic event of this magnitude is not just relegated to astronomers and NASA personnel," said Gary Fujihara, science education and public outreach officer for the University of Hawai'i Institute for Astronomy.

The event may be viewed on television, on the Web and on screens at locations statewide. Astronomers will be on hand at many sites to explain what's going on.

NASA's primary goal is nothing less than to peer into the structure of matter in our solar system at its origin, 4.5 billion years ago, Fujihara said.

"Comets are believed to be the most primitive, unaltered material in the solar system," said Alan Tokunaga, director of the NASA Infrared Telescope Facility. Tempel 1 will be 85 million miles away, nearly as far from Earth as Earth is from the sun. Most of the comet's outer surface has been modified by the sun, but the inside of a comet may be just what it was in the beginning.

NASA will fire an 820-pound, nonexplosive "impactor" from a passing spacecraft, and it should hit Tempel 1 at 23,000 mph. The resulting crater should be bigger than Aloha Stadium. The impactor will have a camera that will record its own approach, and the spacecraft has two cameras that will record what happens at impact.

Comet Tempel 1 is sausage-shaped, 9 miles long and 2.7 miles thick — big enough that the collision should make no appreciable change to its orbital path, astronomers say. They are certain that it will not pose a threat to Earth. But a massive cloud of dust and ice should blast out of the comet, catching the sun's light — that's what will be visible from Earth.

Tokunaga said different Mauna Kea and Haleakala telescopes will be looking for different things, but a key issue is what's inside the comet. That will be determined by studying the reflected light.

"Each molecule emits or absorbs light at a specific wavelength or color," he said. He expects there will be a lot of mineral dust, and ices of water, methane, ammonia, methanol and other compounds, but he can't be sure.

"We've never actually looked into the interior of a comet. Everything we know is about the exterior," Fujihara said.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808) 245-3074.