Year in the stars: 2005

What to expect in the sky this year

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Astronomers ended 2004 with their telescopes ready and their jaws dropping. It was an unexpectedly historic year.

Right now, 2005 seems to pale in comparison, but given the events of the previous year, anything is possible.

Comet Machholz appeared in the sky in December making it the record setting fifth comet visible to the naked eye in 2004.

Amateur astronomer Don Machholz discovered comet Machholz in August with a telescope on his back deck. The comet is still visible in the night sky and will be getting brighter during January.

"We don't know how bright it will get," said Colorado Mountain College astronomy professor Jimmy Westlake. Comet Machholz can be seen in the early night sky, with the best viewing predicted for Friday. "The comet will be positioned right by Pleiades, the Seven Sisters, a constellation that a lot of people recognize."

The comet will be closest to Earth on Jan. 9.

"(Machholz) will be with us for many weeks to come and will be visible to the naked eye," Westlake said.

Westlake photographed the comet in December when it appears as a greenish fuzz ball, "like a dandelion head."

Comets are made of rock and icy mixtures of water and other chemicals. As a comet approaches

the sun, the surface is heated and boils off, creating a tail of gas and dust.

"There are billions of this type of comet out there," Westlake said. Machholz appears to have come from the Oort Cloud -- an immense spherical cloud that surrounds the outer edge of the solar system, extending three light years from the sun but still held in place by the sun's gravitational pull.

"Debris in the Oort Cloud spends most of its life away from the sun, unless a star passes close enough and nudges one of the comets our way," Westlake said. "There are thousands of them that could be heading for the sun that we won't see for a thousand years."

Comet Machholz is the first Oort Cloud comet in recorded history. Other Oort Cloud comets probably passed before humans walked Earth, Westlake said.

After the excitement of Comet Machholz dies down, there are still a few astronomical events to keep people outside and looking up.

Observers will see the first transit of Venus since 1882, and Mars will make a close approach to Earth. Most people will remember the summer of 2001 when Mars hung red and bright in the night sky for months. On the night of Oct. 29, Mars will be the closest to Earth it has been since that memorable summer.

"It will be a big, bright eye-catching object in the evening sky, and there will be a lot in the news about it," Westlake said.

In 2005, there will be a few striking planetary alignments, observable through a set of binoculars. On June 24, Mercury, Venus and Saturn will align.

"On June 27, Mercury and Venus will only be a tenth of a degree apart and will seem to merge into a single point," Westlake said. "They will look like they are so close, even though they are millions of miles apart."

2005 also will be the year of potential discovery made by two space probes. On Jan. 14, the Huygens space probe will parachute into the atmosphere of Saturn's Titan moon.

"Titan has a thick, cloudy atmosphere and is really a planet that orbits around Saturn," Westlake said. "The atmosphere is made mostly of nitrogen, and it may have been a much warmer place when Saturn itself was a miniature sun for Titan."

Saturn cooled off, and Titan went into a deep freeze several million years ago. Titan is 270 degrees below zero on its hottest day.

Huygens will send back data and photographs from Titan as it goes down. It could land on dry ground or in an ocean of liquid methane, Westlake said.

"Titan is a very alien and interesting place," he said. "Scientists are interested to find out more about it."

On July 4, the Deep Impact mission will send a space probe crashing into the surface of Comet Tempel 1. The impact will be so great that it will excavate a crater 30 feet across, exposing the interior of a crater for the first time in history.

"Inside will be matter that is unmodified since formation of our solar system (giving scientists clues about that formation)," Westlake said.

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