Rumours of the demise of Kreutz sungrazing Comet Lovejoy may have been greatly exaggarated. NASA’s Solar Dynamics Observatory caught Comet Lovejoy emerging from its scorching close encounter with the sun. [Video Credit: NASA SDO]
Comet Lovejoy was discovered on Dec. 2, 2011, by amateur astronomer Terry Lovejoy of Australia. Researchers quickly realized that the new find was a member of the Kreutz family of sungrazing comets. Named after the German astronomer Heinrich Kreutz, who first studied them, Kreutz sungrazers are fragments of a single giant comet that broke apart back in the 12th century (probably the Great Comet of 1106). Kreutz sungrazers are typically small (~10 meters wide) and numerous. The Solar and Heliospheric Observatory sees one falling into the sun every few days.
At the time of discovery, Comet Lovejoy appeared to be at least ten times larger than the usual Kreutz sungrazer, somewhere in the in the 100 to 200 meter range. In light of today’s events, researchers are re-thinking those numbers.
“I’d guess the comet’s core must have been at least 500 meters in diameter; otherwise it couldn’t have survived so much solar heating,” says Matthew Knight. “A significant fraction of that mass would have been lost during the encounter. The remains are probably much smaller.”
SOHO and NASA’s twin STEREO probes are monitoring the comet as it recedes from the sun. It is still very bright and should remain in range of the spacecrafts’ cameras for several days to come.
What happens next is anyone’s guess.
“There is still a possibility that Comet Lovejoy will start to fragment,” continues Battams. “It’s been through a tremendously traumatic event; structurally, it could be extremely weak. On the other hand, it could hold itself together and disappear back into the recesses of the solar system.”
Comet Lovejoy skimmed across the Sun’s edge about 140,000 km above the surface late Dec. 15 and early Dec. 16, 2011, furiously brightening and vaporizing as it approached the Sun. It is the brightest sungrazing comet that SOHO has ever seen, with a nucleus about twice as wide as a football field. It unexpectedly survived the pass and cruised out from behind the Sun some hours later. Comets are ancient balls of dust and ice. There is a temporary, four hour gap in the SOHO data after the comet went behind the occulting disk.