Pale green Hartley comet to pass close to Earth

A pale green comet will make a close pass by the Earth, one of the closest approaches of any comet in the past century and giving sky-watchers a good view of the cosmic body.

Hartley 2 is on a course to make its closest pass by Earth at a mere 11 million miles (17.7 million kms) tomorrow, SPACE director CB Devgun said.

During its passage, the comet may be visible to the naked eye at an apparent magnitude of 5, in the constellation Auriga, from a dark moonless sky, he said, adding it was one of the closest approaches of any comet in the past century.

Comet Hartley 2, officially designated 103P/Hartley, is a small periodic comet with an orbital period of 6.46 years. It was discovered by Malcolm Hartley in 1986 at the Schmidt Telescope Unit in Siding Spring, Australia.

A comet is an icy small solar system body that, when close enough to the sun, displays a visible coma (a thin, fuzzy, temporary atmosphere) and sometimes also a tail.

As the comet nears the sun, it may become bright enough to be seen with the naked eye from dark, especially in rural areas where light interference is less and it will appear as a glowing smudge in the sky. And even the smallest optical aid will help see the details, Devgun said.

The comet can be seen few hours before sunrise using binocular facing towards north direction, N Sri Raghunandan Kumar, general secretary of Planetary Society Of India said.

The comet passed a similar distance from the Earth in the year 1066 and was described as appearing "like a moon".

Hartley 2 will next be seen around April 20, 2017.

In a little less than a month, NASA's Deep Impact spacecraft will fly by the comet to image its nucleus and take other measurements. In preparation for this event, both the Wide-field Infrared Survey Explorer (WISE) and the Hubble Space Telescope have imaged the comet, scouting destination for Deep Impact.