Guest in the Sky: Comet 103P/Hartley2

Hartley2 the comet has been appeared in the night sky when it is on a visit to the Sun. Since more than a week now, it has been visible from various parts of the globe. Though, due to lower surface brightness it can been seen with binoculars only from fairly dark areas.

Comet 103P/Harley2 – Credit: M. Jäger #astrophoto on Twitpic

Comet 103P/Hartley2 is a periodic comet with a revolution period of 6.46 years. The comet was discovered by Malcolm Hartley on 1986, who has also been the discoverer of 4 other comets. This comet is the second of three periodic comets Malcolm Hartley has discovered. For this reason, it also goes by the name “Hartley 2.”

Although October marks the peak for Comet 103P/Hartley, the comet will continue to make news in November will get widely discussed in the Astronomer community. NASA’s EPOXI mission will fly past the comet and return stunning images of its nucleus. EPOXI comes closest to the comet November 4, 2010.

Hartley: Today

For some images of comet 103P as it is now, images from Martin Mobberly (UK), Bernhard Haeusler (Germany, possible arc’s in the tail), J.A. HeriquezG. Masi (Italy), and Eric Bryssnick (Beligum). By the end of October the comet should still be around 5th magnitude.


The comet heads to the southeast during October. On the night of October 8/9, in Perseus, a pair of adjacent bright star clusters that will form a beautiful backdrop for the comet. It then passes the bright star Capella in Auriga in mid-October. The comet will pass within 11 million miles of Earth (about 45 times the distance to the Moon) on October 20. During that time the comet may be visible to the naked eye as a 5th magnitude “fuzzy star” in the constellation Auriga about the time it will appear brightest in the sky. Unfortunately, a nearly Full Moon then brightens the sky, making the comet less conspicuous. (PDF File of map)

The Comet Structure

Analysis of the new Hubble data shows that the nucleus has a diameter of approximately 0.93 miles (1.5 kilometers), which is consistent with previous estimates. Comet 103P/Hartley should show two tails emanating from a roughly circular glow, known as the “coma,” which masks the comet’s nucleus. The nucleus is a giant ball of ice and dust that measures about a mile across. As sunlight hits the nucleus, the ice boils off and carries dust with it. This cloud of gas and dust forms the coma.

The Hubble data show that the coma is remarkably uniform, with no evidence for the types of outgassing jets seen from most “Jupiter Family” comets, of which Hartley 2 is a member. Jets can be produced when the dust emanates from a few specific icy regions, while most of the surface is covered with relatively inert, meteoritic-like material. In stark contrast, the activity from Hartley 2’s nucleus appears to be more uniformly distributed over its entire surface, perhaps indicating a relatively “young” surface that hasn’t yet been crusted over.

Hubble Probes Comet 103P/Hartley 2 in Preparation for DIXI/EPOXI Flyby

This Hubble Space Telescope image of comet 103PHartley 2 was taken with the Space Telescope Imaging Spectrograph (STIS) on September 25, 2010. (Credit NASA, ESA, and H. Weaver (JHUAPL))

A Stellarium snapshot of the comet in the sky. This time I could not took it by myself but found it on of the Astronomy enthusiast from Australia Ian Musgrave.

The comet will be seen near the Moon.

I  am hoping for the good observations of the comet taken by Amateurs and of course by professionals from India. All these are also looking forward to the NASA reports on November 4, 2010.

Till then enjoy the Guest in Night SKY.



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