Comet ISON seen through SOHO’s eyes
Just a brief update today. Comet ISON has left the eyes of SOHO, but it’s still there in STEREO-A through Dec. 7 and possibly longer if NASA decides to roll the spacecraft for a better view in the coming days. I checked today but no recent, high-res photos have been uploaded yet. I’ll post them when they arrive. You can still see the comet in the low-resolution picture below.
The last we saw of ISON, it continued to expand and fade on its outbound journey. We should know in a few days what it looks like from Earth’s skies when astrophotographers will be out in force attempting to record and see the comet’s dusty remains.
Meantime, enjoy this wonderful compilation of SOHO (Solar and Heliospheric Observatory) pictures taken with its two coronagraphs – LASCO C2 and C3 – and assembled by Pieter-Jan Dekelver from Belgium. Notice how much faster the comet moves when closest to the sun when ISON feels the sun’s gravitational force most strongly.
The International Astronomical Union published an electronic telegram No. 3731 today Dec. 1 with blow-by-blow scientific observations of ISON’s evolution during perihelion. Here’s a quick summary of the results:
* The comet’s nucleus disrupted hours before perihelion with the comet’s head fading from -2 magnitude (just shy of Jupiter’s brightness) to well below +1 magnitude shortly before perihelion.
* What remains after perihelion is a diffuse cloud of dust from the nucleus mostly transparent to the background stars. Late on Nov. 30 the main part of the cloud spanned about 1/2 degree and glowed weakly at magnitude 5.4.
* Z. Sekanina of the Jet Propulsion Laboratory, studying SOHO images, determined that ISON stopped producing dust 3 hours before perihelion. This jives with the photos taken shortly after perihelion showing that a sharp tip had replaced the larger, rounded nucleus.
* The nucleus or core of the comet is thought to have fragmented shortly before a sudden surge in brightness seen nearly 12 hours prior to perihelion.
* ISON’s post-perihelion, sunward-pointing tail may be composed of dust grains released 1-2 days before perihelion, while the eastward pointing tail (sticking out to the left of the comet) was made of dust released within an hour of perihelion and likely composed of graphite and metals.The streamer of much larger dust grains ejected long before the comet was near the sun completely disappeared during the comet’s near-brush with the sun.