These are exciting times—we’ve had the first ground-based discovery of a Kreutz sungrazing comet since 1970!
CBET 2930 reports the discovery by Terry Lovejoy (Thornlands, Queensland, Australia) of a rapidly brightening comet, now designated C/2011 W3 (Lovejoy). It appears to be one of the famous Kreutz sungrazing comets. These comets have perihelion distances (closest point to the Sun) of tiny fractions of an astronomical unit and are named after Heinrich Kreutz, the German astronomer who proved they were all fragments of a much larger comet that broke up centuries ago. Some come so close to the Sun that they even graze its photosphere.
This group of comets has many famous members, including the Great Comet of 1106; many members from the 1880s, including perhaps the brightest comet of all time, the Great Comet of 1882. There’s even my personal favorite, the Great Headless Comet of 1887, whose nucleus was vaporized at perihelion and persisted as a ghostly comet tail for weeks afterwards. The Kreutz group also includes most of the numerous SOHO comets, and of all the sungrazing groups of comets (the others being the Meyer, Marsden and Kracht groups), the Kreutz are the ones that pass closest to the Sun.
Before the community (and I) gets too excited, C/2011 W3 (Lovejoy) is intrinsically fairly faint. It may not survive its close perihelion passage on December 16th that will bring it within 881,700 km (548,000 miles) of the Sun (its center, that is—comet Lovejoy will pass just 186,200 km from the Sun’s surface); that’s over 50 times closer than Mercury ever gets! However, this comet may never brighten as much as other objects with similar orbits but it must be kept in mind that cometary brightness predictions are fraught with massive uncertainties. Still, being the first sungrazer discovered from the ground in 41 years, it is an event worthy of our attention. And often times in the past, sungrazers have come in clumps; we can only hope that more bright sungrazing comets will be coming our way in the next few years.
You can read about Terry Lovejoy’s discovery in his own words. Incidentally, Terry has now become the first person to discover sungrazing comets with both space and ground-based telescopes, as he is one of the pioneers in discovering comets in SOHO images; the 74th SOHO comet, C/1999 O1 (SOHO), was his first such discovery. Terry also has an asteroid named after him: 61342 Lovejoy.