FLASHBACK

One year ago today, on Oct. 24, 2007, Comet 17P/Holmes shocked astronomers when it suddenly exploded, brightening a million-fold to naked-eye visibility. Within three days of the blast, the comet was bigger than Jupiter, and within three weeks it was larger than the sun itself. Spanish photographers Vicent Peris and José Luis Lamadrid recorded this view on Nov. 1, 2007, using little more than a 7-inch telescope:

What happened to Comet Holmes? Just-released observations by NASA's Spitzer Space Telescope define the mass and velocity of the explosion: "The energy of the blast was about 10¹⁴ joules and the total mass was of order 10¹⁰ kg," says Bill Reach of Caltech. In other words, Holmes exploded like 24 kilotons of TNT and ejected 10 million metric tons of dust and gas into space. These numbers fit a model favored by Reach in which a cavern of ice some hundred meters beneath the comet's crust changed phase, from amorphous to crystalline, releasing in transition enough heat to cause Holmes to blow its top.

ASTEROID FLYBY: "At midnight on Oct. 23rd, I began my lonely vigil," says Dennis Simmons of Brisbane, Australia. "I was hunting for 2008 TT26, a 70-meter asteroid scheduled to pass less than a million miles from our home planet Earth. What I hadn't anticipated was the frantic pace set by the little space rock as it zoomed through my field of view!" He captured this movie using a 9-inch Celestron telescope and an SBIG ST7e CCD camera:

Click on the image for photo details

http://www.spaceweather.com/ 

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