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  Holy suicidal comets!May 14, 2011 12:47 AM PDT | url
 
Added 1 new A* page:Hey, it's the weekend! On Sunday I'll draw and post a new page of my weekend fairy tale comic, "The Princess and the Giant." If you haven't been keeping up, here's a little teaser banner you can click on to go right to the page from last Sunday:
 
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Okay enough princesses--some science just happened in space!
 
First, some background. The SOHO ("Solar and Heliospheric Observatory") satellite--owned by a European industrial consortium, so its photos aren't public domain, blah--launched in 1995 to a gravitationally balanced point between the Earth and the Sun; the Sun is so massive relative to the Earth that this point is actually just 1% of the way to the Sun from Earth! (Interestingly, all of SOHO's gyroscopes failed after an attitude control problem in 1998; fortunately, the mission engineers figured out a way to use its onboard reaction wheels (basically a wheel spinning by means of a motor--this causes the craft to rotate very slightly in the opposite direction due to conservation of angular momentum) to control its orientation, making it the first spacecraft of its type to control its attitude this way.)
 
And now let's go back even further--all the way to 1106, when the Great Comet of 1106 was seen by observers all over the globe--it was quite a comet, apparently. Well, since then, other big comets have been seen along what seems to be a similar trajectory; among recent spottings, these include the Great Comet of 1882
 
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image by David Gill (source)
 
and Comet Ikeya-Seki, aka the "Great Comet of 1965"
 
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image by Maynard Pittendreigh (source)
 
which may have been the brightest comet seen since the great one of 1106. All of these comets pass very close to the sun, and calculations show that these later ones may all be pieces from a breakup of the 1106 comet; as a family they're called Kreutz Sungrazers after the dude who studied them and determined that they were related.
 
SOHO has proven to be very good at spotting these sun-grazing comets; as of 2008, 1500 had been identified, and "more than 75% of the SOHO sungrazers have been discovered by amateur astronomers analysing SOHO's observations via the Internet." Also, they often show up in pairs, which is thought to be the result of a larger one splitting up as it nears the Sun. None of them have survived--they either go into the Sun, or evaporate on their way toward it. Here's a nice SOHO photo of a pair plunging toward their fiery doom.
 
That brings us to Tuesday/Wednesday of this week, when SOHO spotted a Kreutz Sungrazer plunging into the Sun at about the same time that the Sun was shooting out a big coronal mass ejection ("CME"). According to the space.com article, the events weren't related, since the CME started before the comet entered the Sun's magnetic fields, but the conjunction made for a nifty video, which apparently can't be embedded (time to get your stuff together, space.com! :P).
 
For some reason I couldn't seem to find the video on NASA's site, but I did find an article from January describing a comet storm lasting from December 12th to the 22nd, in which 25 comets were spotted plunging into the Sun. Poor lemming-like things! Anyway there's an animated GIF of one of them there (along with another big CME--hm! :P), and more details about Ikeya-Seki and other Kreutz Sungrazer stuff.
 
 
 
 
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