The SOHO (Solar and Heliospheric Observatory) space probe has the primary purpose of keeping an eye on the Sun but when a comet passes close to our star is also useful to track its trajectory. Last week, SOHO identified a new comet because passing near the Sun it’s become bright enough to be detected.
This comet was originally called SOHO-2875 because in the course of over 19 years of mission in a collaboration between ESA and NASA this is the 2875th comet identified by the SOHO space probe. Subsequently officially named C/2015 D1 (SOHO), it survived a flyby with the Sun and may also be visible from Earth in the coming weeks.
The comet C/2015 D1 (SOHO) is interesting because it’s part of a family of comets called Kreutz Sungrazers. According to the most plausible theory, they are the fragments of a single large comet that broke apart centuries ago. It was the astronomer Heinrich Kreutz who studied this family showing evidence of their common origin so it was named after him.
Most comets that come close to the Sun enough to be seen by the SOHO spacecraft don’t survive the passage. They’re called Sungrazers exactly because they approach the Sun so close that typically are torn apart and the ice they contain evaporates completely or almost.
The comet C/2015 D1 (SOHO) passed about 3,5 million kilometers (about 2,2 million miles) from the Sun and at least for now still seems intact. However, it’s still possible for the comet to get torn to pieces. Now it’s moving away from the Sun but the ice it contains is still sublimating in great quantity getting turned into the steam that forms most of its tail.
In 2013, the comet ISON seemed to have to offer the show of the century, only to be torn apart in its flyby with the Sun. Now astronomers hesitate before saying that a comet might be visible from Earth. With a bit of luck, in the coming weeks the comet C/2015 D1 (SOHO) could be seen by ground observers but only it survives for a little longer.