Palomar Observes Broken Comet

PALOMAR MOUNTAIN, Calif.—Astronomers have recently been enjoying front-row seats to a spectacular cometary show. Comet 73P/Schwassmann-Wachmann 3 is in the act of splitting apart as it passes close to Earth. The breakup is providing a firsthand look at the death of a comet.

Eran Ofek of the California Institute of Technology and Bidushi Bhattacharya of Caltech's Spitzer Science Center have been observing the comet's tragic tale with the Palomar Observatory's 200-inch Hale Telescope. Their view is helping them and other scientists learn the secrets of comets and why they break up.

The comet was discovered by Arnold Schwassmann and Arno Arthur Wachmann 76 years ago and it broke into four fragments just a decade ago. It has since further split into dozens, if not hundreds, of pieces.

"We've learned that Schwassmann-Wachmann 3 presents a very dynamic system, with many smaller fragments than previously thought," says Bhattacharya. In all, 16 new fragments were discovered as a part of the Palomar observations.

A sequence of images showing the piece of the comet known as fragment R has been assembled into a movie. The movie shows the comet in the foreground against distant stars and galaxies, which appear to streak across the images. Because the comet was moving at a different rate across the sky than the stellar background, the telescope was tracking the comet's motion and not that of the stars. Fragment R and many smaller fragments of the comet are visible as nearly stationary objects in the movie.

"Seeing the many fragments was both an amazing and sobering experience," says a sleepy Eran Ofek, who has been working non-stop to produce these images and a movie of the comet's fragments.

The images used to produce the movie were taken over a period of about an hour and a half when the comet was approximately 17 million kilometers (10.6 million miles) from Earth. Astronomically speaking the comet is making a close approach to Earth this month giving astronomers their front-row seat to the comet's break up. Closest approach for any fragment of the comet occurs on May 12, when a fragment will be just 5.5 million miles from Earth. This is more than 20 times the distance to the moon. There is no chance that the comet will hit Earth.

"It is very impressive that a telescope built more than 50 years ago continues to contribute to forefront astrophysics, often working in tandem with the latest space missions and biggest ground-based facilities," remarks Shri Kulkarni, MacArthur Professor of Astronomy and Planetary Science and director of the Caltech Optical Observatories.

The Palomar observations were coordinated with observations acquired through the Spitzer Space Telescope, which imaged the comet's fragments in the infrared. The infrared images, combined with the visible-light images obtained using the Hale Telescope, will give astronomers a more complete understanding of the comet's break up.

Additional support for the observations and data analysis came from Caltech postdoc Arne Rau and grad student Alicia Soderberg.

Images of the comet and a time-lapse movie can be found at:

http://www.astro.caltech.edu/palomar/images/73p/

Contact:

Scott Kardel Palomar Public Affairs Director (760) 742-2111 [email protected]