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INCOMING CME: Decaying sunspot 1060 delivered a parting shot on April 8th. The active region's magnetic field erupted, sparking a B3-class solar flare and hurling a faint coronal mass ejection (CME) almost directly toward Earth. Geomagnetic disturbances are possible when the cloud arrives on April 11th or 12th. [UPDATED: aurora gallery]
SUNGRAZING COMET: Today, the sun had a comet for breakfast. The icy visitor from the outer solar system appeared with no warning on April 9th and plunged into the sun during the early hours of April 10th. One comet went in, none came out. The Solar and Heliospheric Observatory (SOHO) had a good view of the encounter:
Click to launch a movie
The comet was probably a member of the Kreutz sungrazer family. Named after a 19th century German astronomer who studied them in detail, Kreutz sungrazers are fragments from the breakup of a giant comet at least 2000 years ago. Several of these fragments pass by the sun and disintegrate every day. Most are too small to see but occasionally a big fragment like today's attracts attention.
This has been an active year for big, bright sungrazers. There was one on Jan. 4th, one on March 12th, and now one today. Normally we see no more than 3 or 4 bright ones in a whole year; now we're seeing them almost once a month. It could be a statistical fluctuation or, maybe, a swarm of Kreutz fragments is nearing perihelion (closest approach to the sun). Stay tuned for doomed comets!
SHUTTLE CLOUD: On April 5th, space shuttle Discovery blasted off from Cape Canaveral at the crack of dawn. The shuttle began its journey in darkness--the sun was still below the horizon--but moments after it left the pad, Discovery burst into high altitude sunlight and proceeded to put on an extraordinary show. University of Florida astronomy professor Howard Cohen describes what he saw from his home in Gainesville, more than 130 miles from the Cape:
"The launch began in typical fashion- a brilliant, yellowish glow rising out of the southwest gradually morphing into a white contrail. Impatient observes might have thought that was it. But then an amazing contrail, the likes of which I have never seen before, rapidly appeared around and following the shuttle's path. For a short time it resembled a comet streaking across the dawn sky." He took this picture using his Canon EOS 5D:
Photo details: Canon EOS 5D Mark II, 190 seconds, ISO 800.
"In binoculars the view was stunning and chilling," Cohen continues. "It was like viewing a comet traveling in fast motion -- I could see the contrail unfolding, glistening and wavering behind the shuttle. Unlike some who might have thought something might have gone wrong, this never entered my mind. I could easily see the shuttle unhesitatingly moving forward."
Atmospheric optics Les Cowley believes the cloud formed when the shuttle entered the mesosphere. Water vapor spewing from the shuttle's main engines began to freeze, forming crystals of just the right size to scatter sunlight and produce the iridescent colors shown in so many photos.
"I think we had a 'perfect storm' for this launch," concludes Cohen. "Atmospheric conditions including probably cold and moist air, clear skies and especially sunlight at just the right angle produced this unique effect. Unfortunately, with the shuttle program coming to an end, we probably will not see this again."
April Northern Lights Gallery
[previous Aprils: 2009, 2008, 2007, 2006, 2005, 2004, 2003, 2002]