Comet 103P or most commonly known as Comet Hartley will make its nearest approach this October. It will be the brightest comet of the year 2010. Comet 103P/Hartley was discovered by Australian astronomer Malcolm Hartley in 1986. The comet has a period of 6.5 years, traveling just outside the orbit of Jupiter to nearly Earth's distance (1 AU) from the Sun. The year 2010 marks its 4th return since it was discovered, and this year is said to be its best so far.
The comet will be visible to the naked eye under a dark sky (around mag 5) as it treks a path along the constellation Cassiopea moving southeast to the constellation Gemini. Use of a binoculars will give a good view of the comet, and telescopes would be able to reveal details. Here is an image of Comet Hartley's trajectory from astronomy.com:
The comet can actually be spotted now (Sept) in Cassiopea. On October 9 it will appear in the foreground of the double cluster in Perseus. On October 20 it will be in its closest distance to the Earth and will appear in its maximum brightness, unfortunately the full moon is on Oct 23 meaning the almost full moon will make the comet less conspicuous.
In November, NASA's EPOXI [Extrasolar Planet Observation and Characterization and the Deep Impact Extended Investigation] mission will fly past the comet and return stunning images of the comet nucleus. NASA approved the retargeting of the EPOXI for a flyby on Oct. 11., after the initial target (Comet Boethin) could not be found.
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Observer Rolando Ligustri remotely photographed 103P/Comet Hartley 2 on September 6th (Universal Time) using a 10-inch f/3.4 Takahashi Epsilon 250 astrographic telescope.
