Comet to do a fly-by in western sky

The brightest comet in 30 years is streaking toward the sun, and Western Washington's chronic clouds may part long enough to provide a good view tonight.

Comet McNaught should be visible at sunset in the western sky, said Steve Van Rompaey, of the Seattle Astronomical Society. But it won't be easy to spot, even though the National Weather Service is forecasting clear skies.

"It's really hard to observe, because it's so close to the sun," Van Rompaey said.

The key is to look just above the horizon shortly after the sun goes down. "You can't wait until it gets dark," he said.

The comet is bright enough to be visible to the naked eye even at twilight. Binoculars will enhance the view, revealing the glowing coma of dust that surrounds the comet's head, as well as its long, sweeping tail.

Van Rompaey also advises a high vantage point, if possible.

The comet is so bright that Mary Singer, of the Spokane Astronomical Society, at first mistook it for an airplane when she got a glimpse Tuesday night through broken clouds.

"It had the most glorious, long, bushy tail you'd ever want to see," she said. "It looks just like everybody's fantasy of a comet."

Another Spokane-area stargazer reported that after the comet's body sank below the horizon, the tail was still visible, Singer said.

Friday is forecast to be partly cloudy and might also provide a viewing window. After that, the comet will disappear as it rounds the sun. The best views will then be in the Southern Hemisphere, where the comet may be bright enough to be seen during the day.

The surprising intensity is because of the comet's proximity to the sun. McNaught is projected to pass within 15.8 million miles of the sun, closer even than the planet Mercury. Made up of ice and rock left over from the formation of the solar system, comets glow and produce a tail when exposed to the sun's radiation.

The comet was a faint point of light when it was discovered Aug. 7 by Australian astronomer Robert McNaught. It is notoriously difficult to predict how bright a comet will become, as anyone who remembers comet Halley's less-than-stellar performance in 1986 can attest.

Comet McNaught is already brighter than comet Hale-Bopp, which was visible in the Northwest for weeks in 1997.

The only downside to comet-watching tonight will be temperatures that dip well below freezing, said National Weather Service meteorologist Johnny Burg.

"Anyone out there to look at the comet is going to pay for it," he said.

But hard-core astronomers scoff at the cold.

"That won't stop us," Van Rompaey said.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com