Astroblog: No, fragments of 73P will NOT hit the earth.

Sunday, April 30, 2006

No, fragments of 73P will NOT hit the earth.

Image Credit NASA/ESA/STScI (click to enlarge).

In the wake of the mssive disintergration of some of 73P's fragments, a few people have been asking if some of the smaller chunks may hit Earth.

The answer is a resounding no!. The reason can be seen in the Hubble image in this post and the spectacular video page, where you can seen an animation of 73P-B breaking up over 3 days. Go now, my favorite is the medium quality MPEG). As you can see, while 73P-B produces a spectacular number of small fragments, mots of them remain cloase to the parent body. Several of them seem to evaporate completely over this 3 day time fame (eg the fragment bottom right).

The fragments that do survive are gravitationally bound, they will follow 73P's orbit around the Sun and won't hit us. Have a look at the Celestia image below to see the relative postions of the comet and Earth.

As you can see in the Celestia image (using the latest ephemeris), even at closest approach the fragments are quite some distance from Earth. At closest approach for spectacularly fragmenting 73P-B, the comet is 0.067 AU, about 26 times the distance from the Earth to the Moon. Now some of those fragments are travelling sideways, but to have any chance of hitting earth, they have to be traveling at around 8 kilometers per second in our direction, and you can see from the images they are drifing much more lazily than that.

Celestia simulation of 73P at time of fragment C's closest approach to Earth (click to enlarge).

Will we get a meteor shower from 73P? Over on the comets list Carl Hergenrother points out that 73P is the parent body of the Tau Herculid meteor shower, which only occasionally produces meteors. Recent studies suggests that there will be no enhancement of the Tau Herculids this year (if they can be seen at all).

There will be significant Tau Herculid activity in 2022, but this will be due to particles released in 1892. We will probably not enocounter the debris fro either the 1995 or 2006 breakups for quite a long time.

# posted by Ian Musgrave @ 8:35 am