On December 21st, both the Solar Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory Ahead (STEREO-A) observed the demise of a bright Sungrazing comet, presumably a Kreutz-group member! Moreover, the comet was accompanied by four small fragments, all which vanished along with this bright comet.
Animation of the bright new Sungrazing comet, and its four tiny fragments (marked by the black lines)! These were some the last images of these comets before their demise. Image credit: ESA/NASA SOHO/LASCO C2.
The bright comet was discovered in the publically available SOHO/LASCO C3 images on December 19th, by Polish amateur astronomer Szymon Liwo. At the time the discovery images were taken the comet was still very faint, but it quickly brightned over the next couple of days to become a magnificient object!
Extract of one of the discovery SOHO/LASCO C3 images of the bright comet (circled). Notice the dense starfield of the Milky Way in the background! Image credit: ESA/NASA SOHO/LASCO C3.
Only several hours before the comet’s demise, Masanori Uchina (Japan) and Worachate Boonplod (Thailand) reported three faint surrounding fragments in SOHO/LASCO C3 and C2 images. The 4th one was reported by yours truly a day later, in SOHO/LASCO C2 images, after having spotted it in STEREO/SECCHI HI1-A frames. However, all fragments appeared best in the SOHO/LASCO C2 images (see animation above).
Animation of all 5 comets in STEREO/SECCHI HI1-A diff images. All the four faint fragments are marked by the red lines. One of them is only partially distinguishable from the bright comet. The first one to leave the Field-of-view was discovered in these images. Notice the intense solar outflow entering the FOV. Image credit: NASA/NRL STEREO/SECCHI HI1-A.
All five comets were visible in STEREO/SECCHI HI1-A images. Personally, I found some of them difficult to spot in those images, but they were definitely all there! The comet I reported was perhaps the most difficult to observe (as its clearly the faintest of them all). When I first found it in STEREO, I thought it was one of the previously known 3 fragments, until I noticed those were located elsewhere in these images! I wasn’t convinced by its appearance in STEREO, so I searched for it in SOHO/LASCO C2 images, where it definitely appeared. Hence I reported it in those images.
More than being used to recover all of the four fragments, the STEREO gave us a stunning view of the bright comet. In these images, not only did we observe a long tail (like in SOHO/LASCO), but the tail dynamics were very obvious (see animation below). This is caused by the interaction between the comet and the intense Solar wind.
Animation of the bright comet as seen in STEREO’s HI1-A images. Notice how the Solar wind interacts with the comet’s tail, causing it to continuosly move! Notice how some of the fragments are also apparent in these images. Image credit: NASA/NRL STEREO/SECCHI HI1-A.
Like SOHO/LASCO C2, the STEREO/SECCHI CO2-A telescope also captured the comet’s very last moments. Below is an animation of the comet’s diesntigration as seen in these images. The small fragments were too faint to appear in these images.
Animation of four COR2-A frames showing the demise of the bright comet. Image credit: NASA STEREO/SECCHI COR2-A.
The comets are most likely members of the Kreutz-group, a vast family of comets resulting from the continuous fragmentation of a bright sungrazing comet observed millenniums ago. These account for about 85% of all Sungrazing comets observed by SOHO. The family includes many “Great comets”, most notably C/1882 R1, C/1965 S1 (Ikeya-Seki) and C/2011 W3 (Lovejoy)!