Another Big Week Ahead for Comet Hartley 2

Periodic comet Hartley 2 has been getting a lot of attention during the last month as it steadily brightened and passed close to Earth on October 20. But the show is not over yet, as two significant events will be occurring during the period of November 2 to 4.

The biggest event of the week occurs on November 4, when the Deep Impact spacecraft will pass only 434 miles from the comet. The spacecraft made news on July 4, 2005, when it launched a probe that slammed into periodic comet Tempel 1. Following that fly-by, the Jet Propulsion Laboratory (Pasadena, California, USA)  looked for another possible target to study and, eventually, comet Hartley 2 was chosen.

This will be the fifth comet visited by a spacecraft and, although it is the smallest (diameter 0.93 mile) comet to be studied by spacecraft, it will be the most active comet seen up close. When the spacecraft is nearest the comet, it will be able to detect features as small as 20-25 feet across. Recent images of the nucleus using the massive Arecibo Radio Telescope (Puerto Rico) reveal that the nucleus is shaped like a bowling pin.

The other event that will occur next week is a possible meteor shower from Hartley 2.

The possibility of a meteor shower was first predicted by amateur astronomer Joe Rao back in October 1997. He noted that the comet had passed 34 million miles from the giant planet Jupiter during December 1992, which slightly altered the comet’s orbit so that Earth would nearly cross it on November 2/3 of each year.

It has long been known that meteor showers are produced by comets. Every time a comet passes close to the sun, the heat melts the comet’s icy surface and releases large quantities of dust. This dust remains in the comet’s orbit and, if Earth passes near enough to the orbit, a meteor shower can be seen.

So, would a meteor shower occur in 2010? The concern was that the comet had not been in the present orbit long enough for the dust to spread far away from the comet, so astronomers have been cautious in promoting this. Opinions changed a bit on October 27, when it was announced that two fireballs photographed on October 16 were found to have come from orbits resembling that of comet Hartley 2.

Both fireballs had been photographed by multi-camera surveys…one in Canada and the other in the southern United States. Because each fireball was detected by several cameras it was possible to triangulate the point in the sky from which they originated, as well as their velocity. This enabled the orbits they had been moving in prior to their encounter with Earth to be determined. As it turns out, both meteors were moving in orbits very similar to comet Hartley 2. Even more interesting, is that other fireballs have been reported by several individuals during the last couple of weeks, including a flurry on the night of October 25/26. So, for now, astronomers are keeping their fingers crossed in the hope that a good meteor shower is about to occur.