SOHO Solar Pick

Find One, Get Two Free: the latest discoveries on offer from SOHO

(August 12, 2020) On the left, an animation of the comets (click on it to view larger size). On the right, a still shot identifying the comet and the fragments. Credits: ESA/NASA/SOHO/Karl Battams Movie: LASCO C3 (compilation) (MP4, 61M)

UPDATE (31 Aug 2020): COMETS HAVE BEEN NAMED!

The Minor Planet Center (MPC) published the comet designations (see details here) as follows:

SOHO-4049 == C/2020 P4-A (SOHO)

SOHO-4050 == C/2020 P4-B (SOHO)

SOHO-4052 == C/2020 P4-C (SOHO)



First appearances can be deceiving, and one of the latest comet discoveries by SOHO is the perfect example of that!

SOHO is no stranger to discovering new comets - via the NASA-funded Sungrazer Project, the observatory has discovered over 4,000 previously unknown comets since launch in 1995. Most of SOHO's comet discoveries can be categorized into families, or groups, the most famous being the "Kreutz" sungrazer group which accounts for over 85% of the Project discoveries. Only around 4% -some 175 comets- do not appear to belong to any known group or comet family. However, these are often among the most interesting comets and this most recent discovery -SOHO's 4,049th comet- was no exception!

The comet was first spotted on August 5th, 2020, by amateur astronomer Worachate Boonplod. At discovery, it was just a tiny faint smudge near the edge of the C3 coronagraph images recorded SOHO's Large Angle Spectrometric Coronagraph (LASCO) instrument. As it neared the Sun over the next day or so, the smudge became increasingly elongated, ultimately hinting that it may be two comets pretending to be one!

This was confirmed as the comets entered the narrower field of view of the LASCO C2 camera, where the improved resolution confirmed that not only was this more than one comet, it was actually THREE comets! The two main components are easy to spot, with the third a very faint, diffuse fragment following alongside the leading piece.

The comet also showed up in images from the Heliospheric Imager (HI-1) camera on NASA's STEREO mission, sporting a long dynamic tail that we see interacting with the solar wind in these processed images from August 5-9, 2020.

Click on the animation to view larger size or view/download the MP4 version (6.4M).

DID YOU KNOW ? While it is the duty of the Sungrazer Project to record the comets and astrometric observations, declaration of their orbit and their official name is the sole responsibility of the International Astronomical Union's Minor Planet Center (MPC). The MPC is the official worldwide organization in charge of collecting observational data for minor planets (such as asteroids), calculating their orbits and publishing this information via the Minor Planet Circulars.

It's actually not that unusual for SOHO to observe close pairs of comets - we see it quite frequently with the Kreutz sungrazers. But it is extremely rare that we see a "non-group" comet like this.

The SOHO comet-cluster has since moved further from the Sun and faded from sight, and is unlikely to be visible from Earth except perhaps in the most powerful of ground-based telescopes. Its fragmentation probably happened quite recently, exposing lots of primitive volatile ices and gases to the intense sunlight and leading to it becoming quite bright in the LASCO cameras. Unfortunately, the prognosis for small fragmenting comets like this is not good. This was probably this comet's first and last pass by the Sun, as it has likely now crumbled away entirely. But SOHO will continue to keep watching the Sun, and waiting for our next special cometary offering to come along.

The International Astronomical Union's (IAU) Minor Planet Center (MPC) is the organization which will determine its orbit and its official designation. We hope to have this information by early next week and we will also update this page.

By Karl Battams

Manager of NASA's citizen science Sungrazer Project.