• Comet captured on video

    By Alan Boyle, Science Editor, NBC News

    You've seen the stunning still photos from the Deep Impact probe's close encounter with Comet Hartley 2 on Thursday. Now watch the movie. Today NASA released a video clip that shows how the comet looked as the spacecraft approached to within 435 miles, then journeyed away again. The version above slows down the motion and loops the arrival and departure three times. You can clearly see the jets of gas streaming out from the sun-warmed, peanut-shaped iceball.

    The researchers who took part in Deep Impact's EPOXI flyby mission say they'll learn a lot about the nature of comets and the origins of the solar system. And who knows? There might be still another mission awaiting Deep Impact, which took on the Hartley 2 flyby after shooting a bullet at another comet, Tempel 1, five years earlier. To keep up with the mission and the pictures it's still sending back to Earth, click on over to the EPOXI website as well as the mission's Facebook page.

    Here's another video clip from MSNBC's "Countdown," in which Franklin Institute astronomer Derrick Pitts talks about the significance of the comet encounter.

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    amazing, just amazing!

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  • Comet's tale isn't over yet

    Nick Howes

    Comet Hartley 2 exhibits a green coma as well as a reddish tail in this picture from British astrophotographer Nick Howes.

    By Alan Boyle, Science Editor, NBC News

    Comet Hartley 2's close approach to Earth wasn't as spectacular as some might have expected, but the real show should come in a couple of weeks, when NASA sends a spacecraft past Hartley 2 for some ultra-close-ups.

    Skywatchers had been hoping that the comet would become bright enough to see with the naked eye by the time it zoomed past Earth. But even at its closest -- 11.2 million miles as of 8 a.m. ET Wednesday -- you would have needed a pair of binoculars to get a decent view.

    Seeing Hartley 2 is even more challenging now that the moon is getting close to full. "Glaring moonlight will make the comet difficult to observe for the next week at least," SpaceWeather.com's Tony Phillips writes. The fact that the comet is so close to Earth isn't necessarily an advantage. That just means the comet's glow is spread out over a wider area of the sky.

     What's more, the comet hasn't developed a dramatic tail ...yet. You can just make out a tail of streaming reddish dust in the photo above, captured by British astrophotographer Nick Howes early today. As the comet nears its closest approach to the sun on Oct. 28, it may well develop a more prominent tail.

    But the best view of Hartley 2 is likely to come just before 10 a.m. ET Nov. 4, when NASA's DIXI/EPOXI spacecraft is due to pass within 450 miles (700 kilometers) of the comet's nucleus. There'll be tons of observations made between now and the big day, as outlined in the EPOXI team's schedule of events.

    For the latest comet imagery, keep tabs on the EPOXI Facebook page -- and watch for more from the EPOXI website in the days leading up to this year's coolest cometary close encounter.

    Bonus round: SpaceWeather.com explains why Hartley 2 has that green glow. It's because the jets spewing out from the comet's nucleus contain cyanogen, a poisonous gas found in many comets, as well as diatomic carbon (C2). Both substances glow green when illuminated by sunlight. The reddish color of the tail is due to sunlight reflected by the dust streaming from the nucleus. Click the links on SpaceWeather.com's webpage for more views of the comet from around the world.

    More about comets:

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