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Thursday December 15, 2011 8:30 am
Watch a bright comet head for the sun
Soon after Australian amateur astronomer Terry Lovejoy discovered a comet in an automated search program using a telescope equipped with a CCD detector on Nov. 27, it became clear that he had found something special.
Follow-up observations determined that the comet belonged to the Kreutz group of sungrazing comets, so called because members of this comet family—which all travel in similar orbits—pass extremely close to the Sun. The brightest Kreutz comets, such as the great comets of 1066, 1843, 1882, and 1965, have been among the most spectacular comets on record. The Kreutz group is believed to be the remnants of what was once a single, larger comet that has progressively fragmented over the past couple thousand years.
Although Lovejoy's comet—now officially known as C/2011 W3 (Lovejoy)—is not expected to rival the greatest Kreutz comets, it’s the first sungrazer to be found by a ground-based observer in over 40 years, and it should put on an impressive show online. It’s now visible in the images of several spaceborne observatories that monitor our star—the twin STEREO spacecraft and the Solar and Heliospheric Observatory (SOHO)—and should brighten as it makes what’s likely a suicidal run at the Sun.
This comet is Lovejoy’s third official comet discovery. In 2007 he became the first amateur astronomer to find a new comet using a digital SLR (a Canon Digital Rebel with a telephoto lens), and his second find was also with a DSLR. In 1999, he became the first amateur to find a comet in images from SOHO, soon after that satellite started posting its images online. It was a small Kreutz sungrazer, maybe about 10 meters in diameter.
The vast majority of the more than 2,000 pygmy comets found in SOHO since then have also been found by amateurs scouring the images on their home computers, and most have also been tiny Kreutz comet fragments. Lovejoy’s current comet is considerably larger, maybe about 200 meters in diameter.
Comet Lovejoy has now entered the field of view of SOHO’s wide-field LASCO C3 camera, and can be seen, with tail extended below it, as the bright vertical streak at the bottom of the field, as in the illustration that accompanies this story. The instrument is a coronagraph, which uses an occulting disk to block the Sun, revealing the solar corona as well as any stars, planets—or comets—that may be in the Sun’s vicinity.
Over the next two days, the comet will arc upwards towards the Sun, and disappear behind the occulting disk. By then it will have entered SOHO’s narrow-field (LASCO C2) field of view, where it will continue its run at the Sun. At its closest approach, it will pass perilously close to the Sun’s surface and will likely be vaporized; most astronomers don’t expect Comet Lovejoy to survive its passage by our star.
Although bright in SOHO images, Comet Lovejoy is lost to Earthbound eyes in the glare of the Sun. Astronomers may be able to pick it up telescopically when at its brightest, even in daylight. But that can be a perilous undertaking, due to the comet’s proximity to the Sun—looking directly at the Sun, even without optical aid, can result in permanent blindness. Fortunately, we have a safe way to view this event, a ringside online seat to what is likely Comet Lovejoy’s death-plunge towards our star.
New images are uploaded regularly; the comet is visible in the blue LASCO C3 ones and will appear in the orange LASCO C2 images on Thursday. The GIF movies will show animations of the comet’s motion; it’s already visible at the end of the LASCO C3 movie.
This article, written by Tony Hoffman, originally appeared on PCMag.com and is republished on Gear Live with the permission of Ziff Davis, Inc.
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