FARSIDE SOLAR ACTIVITY: Two spectacular CMEs billowed away from the farside of the sun on Sept. 5th: movie. The source was farside sunspot AR3413, which has become hyperactive only days after turning away from Earth. The two CMEs appear to be heading in the direction of sundiving Comet Nishimura; see below! Solar flare alerts: SMS Text
THE SUN JUST RIPPED OFF A COMET’S TAIL: Comet Nishimura (C/2023 P1) is getting close to the sun–and it shows. On Sept. 2nd, a solar storm hit the comet at point blank range and ripped off its tail. Astrophotographer Michael Jaeger recorded the event from AZM Martinsberg, Austria:
Researchers call this a “disconnection event.” It’s caused by a CME (or fast solar wind stream) hitting the comet. One of the earliest recorded examples of this phenomenon occured in April 2007 when NASA’s STEREO-A spacecraft watched a CME strike Comet Encke and rip its tail completely off: movie.
Comet Nishimura is plunging toward the sun for a 0.22 AU close encounter on Sept. 17th. Right now, it is about halfway between the orbits of Mercury and Venus (0.48 AU) where CMEs are denser and stronger than they are when they reach Earth at 1.0 AU.
The CME that hit Comet Nishimura probably came from active sunspot AR3413, which is almost directly facing the comet. This CME, in particular, had the right timing and direction to cause the disconnection event Jaeger observed:
Nishimura’s tail has since grown back–but it might not last for long. More CMEs are heading its way. SOHO recorded at least two moving in the right general direction on Sept. 5th. Experienced amateur astronomers who photograph Comet Nishimura in the early morning sky (observing tips, sky map) may be able to record their impact. Got a picture? Submit it here.