The sun is no longer the largest object in our solar system. At least for a while anyway. Comet 17P/Holmes suddenly exploded on October 23, making it a million times brighter within a few hours and causing its gas and dust cloud to expand until it was measured at 0.9 million miles across by November 9 by Rachel Stevenson, Jan Kleyna and Pedro Lacerda of the University of Hawaii Institute for Astronomy. And it's still growing. The sun's diameter is about 864,900 miles.
The comet should begin to shrink back to a more normal size in the near future. The nucleus of comet 17P/Holmes is made of ice and rock and is just 2.3 miles in diameter. Astronomers theorize that a large chunk of the comet broke off and disintegrated into tiny dust particles.
Here's a larger version of this image. The images of the sun and Saturn are courtesy of ESA/NASA's SOHO and Voyager projects). The comet image is from the Canada-France-Hawaii telescope on Mauna Kea, Hawaii. Here are more details from the University of Hawaii's David Jewitt.
Photo by University of Hawaii/CFHT
