Green Comet approaching Earth

APPROACHING COMET: Green comet 103P/Hartley 2 is approaching Earth for a close encounter on Oct. 20th. At that time, the comet will be only 11 million miles (0.12 AU) from our planet and should be dimly visible to the naked eye from dark sky sites. It already looks great through backyard telescopes.

NASA's Deep Impact/EPOXI spacecraft is en route to this comet for close-up studies and a daring flyby on Nov. 4th.

Periodic comet 103P/Hartley 2 is classed as a young, dwarf comet, with a nucleus roughly 1.14 kilometers across. It belongs to the Jupiter family of comets (comets with periods less than 20 years). The comet was discovered in 1986. Although it then had an orbital period of 6.3 years, an analysis of its orbit reveals the period had been longer in the recent past. During the early decades of the 20th century, the orbital period had been 9.3 years. A close approach to Jupiter in August 1947 (0.22 AU) reduced the period to 7.9 years, while another close approach during April 1971 (0.09 AU) reduced the period to 6.1 years. The comet has been seen at every return since its discovery. The 2010 return is exceptional, as the comet will pass 0.12 AU from Earth on October 20. The Deep Impact space craft will pass about 1000 kilometers from the comet on November 4.

Comet 103P/Hartley 2 will pass 0.12AU from Earth, a mere 11 million miles in October of this year. The near approach allowing even a modest comet to become quite bright. Predictions are that the comet will be brighter than 5th magnitude, easily visible to the unaided eye from a dark site.

Too cloudy to see Comet Lulin

It's been far too cloudy for the past three days to see Comet Lulin where I live. How about you?

Thunderstorms are expected to drown out one of the most exciting evenings for local astronomers.

Suzanne Willis, interim chair for the Department of Physics, said Comet Lulin, discovered in July of 2007, will be most visible to the naked eye tonight between the hours of 8 and 10 p.m.

Willis said Lulin, which is located near the orbit of Saturn, will make its nearest pass by earth before leaving our range of visibility for good. Sadly for the Midwest region, Lulin will not be easily detectable through the storms this evening.

“Lulin is now observable to us for the first time, and it will be the last in a matter of a few weeks,” Willis said. “Comets are on very long orbits often for periods of 100 years, Halley’s Comet included.”

Visibility of Comet Lulin is best achieved with a very dark sky and binoculars to enhance details of the comet, Willis said.

According to National Geographic Daily News, Lulin could be on its first pass by the sun.

“As the object is exposed to the sun’s heat for the first time, its ices will vaporize, possibly causing the comet to brighten rapidly or even break apart,” the Daily News reported.

Astronomy for beginners - Comet Facts

Comet Facts

I've gathered a few comet facts to publish here on astronomy for beginners. Of course comets are often only visible for a short number of days in a normal year, but when a particularly important comet passes by then it makes for quite an astronomical occasion.

Fact1: A comet is a conglomerate of particles bound together by ice (not necessarily H2O water ice, it could be dry ice (CO2), for example)

Fact2: When a comet approaches the sun the ice melts and releases the particles from the main body.

Fact3: The tail of a comet always points away from the sun.

As the picture below shows, there are in fact two tails, both curved, and they are 30 MILLION kilometres long. That's a lot of fine particles. The theory is that the solar wind is responsible for the blue gas and gravity alone for the larger particles.