Comet Movie

The 2006 Apparition of Comet 73P/Schwassmann-Wachmann

Here's the second example of my not widely shared observations made at Winfree Observatory at Randolph Macon Woman's College (now called Randolph College).

On the night of April 27, 2006 fragment C of comet 73P/Schwassmann-Wachmann 3 was in the constellation Corona Borealis. (Just for fun, say Schwassmann-Wachmann five times fast. Pronounce the w's like v's.)

Location of comet 73P/Schwassmann-Wachmann left of Corona Borealis on April 27, 2006 (click to enlarge)

The comet's strange name actually has specific meaning.This was the 73rd periodic comet ever discovered, hence 73P. The comet was discovered on photographic plates taken May 2, 1930 at the Hamburg Observatory by Professor A. Schwassmann and A.A. Wachmann, hence 73P/Schwassman-Wachmann. It was their third periodic comet discovery, hence 73P/Schwassmann-Wachmann 3.

Between 9:26 PM and 11:26 PM on this 2006 April evening I took 25 sixty-second exposures of the comet through a photometric R-filter using a CCD camera on Winfree Observatory's 14-inch telescope. Here's a picture of the telescope and camera that imaged the comet.

Winfree's Celestron-14 telescope equipped with an SBIG ST1001E CCD and ST4 autoguider in 2006

Comets orbit the Sun. When we view comets from Earth we see them move against the background of distant stars. Below is the movie I made from my 25 images. It shows two hours of the comet's orbital motion.

Fragment C of comet 73P/Schwassmann-Wachmann 3: two hours of orbital motion

Comet 73P/Schwassmann-Wachmann 3 was breaking apart in the spring of 2006. Here is a Spitzer Infrared Telescope picture from May 4, 2006 spanning about 6 degrees along the comet's orbit showing 45 of the 60 or more fragments stretched out in a line, all orbiting the Sun, all having tails pointing away from the Sun.

The brightest fragment at top right is fragment C. The next brightest fragment is fragment B.

Here's a Hubble Telescope image from April 18, 2006 showing fragment B breaking apart.

How can a comet fall apart like this? It must be rather loosely held together by gravity, perhaps like the 600-meter long asteroid, Itowkawa, imaged in 2005 by the Japanese Hayabusa Mission:

The Itokawa "rubble pile" asteroid

Another view of the Itokawa "rubble pile" asteroid

If comet 73P/Schwassmann-Wachmann broke apart so drastically in 2006, what will be left when it returns for its next appearance in the fall of 2011?