C/2012 E2 (SWAN)

Lore & Background

On 8 March 2012, Ukrainian amateur astronomer Vladimir Bezugly reported an unknown comet in three images taken by the SWAN instrument on board the SOHO spacecraft. Further study revealed it was a Kreutz group sungrazer with a perihelion date of 15 March 2012. This was particularly interesting because no Kreutz sungrazer had ever been bright enough to be observed by the SWAN cameras, not even the naked-eye Comet C/2011 W3 (Lovejoy) three months earlier, suggesting Comet SWAN might be exceptionally bright.

The SECCHI HI1 camera on STEREO-B first observed the comet on March 11, appearing reasonably bright but not as bright as hoped. It entered the LASCO telescopes' field of view on 13 March, where it was fainter than Comet Lovejoy at the same orbital stage, though brighter than most Kreutz sungrazers. It reached a maximum apparent brightness of mag +1 before declining due to disintegration; the comet did not survive perihelion. SECCHI's COR instruments on both STEREO spacecraft observed its final moments.

The reason for the comet's brightness in SWAN remains unknown, though it is thought to have experienced an outburst a few days before discovery. No ground-based observations were available. Due to a short two-day observation arc, the long-term trajectory is poorly constrained, and the orbital period is unknown.

Reader's Guide

C/2012 E2 (SWAN) holds significance as the first Kreutz sungrazer detected by the SWAN instrument, a milestone that highlighted the instrument's capability to observe comets that were previously too faint. Its discovery by an amateur astronomer using publicly available SWAN images underscores the role of citizen science in solar system astronomy. The comet's unexpected brightness in SWAN, despite being fainter than Comet Lovejoy in later observations, suggests a possible outburst shortly before discovery, though the cause remains uncertain. Its failure to survive perihelion, after reaching mag +1, adds to the understanding of Kreutz sungrazers' fragility. The short observation arc and poorly constrained orbit limit long-term trajectory analysis, but the event demonstrated that SWAN could detect comets not visible to other instruments, opening new avenues for sungrazer detection. The comet's legacy lies in its unique detection path and the questions it raises about outburst mechanisms in Kreutz comets.

Did You Know?

• C/2012 E2 (SWAN) was the first Kreutz sungrazer ever observed by the SWAN instrument.
• It was discovered by Ukrainian amateur astronomer Vladimir Bezugly in publicly available SWAN images.
• The comet reached a maximum apparent brightness of mag +1 before disintegrating and did not survive perihelion.
• Its orbital period is unknown due to a short two-day observation arc.