COMET ISON -3 DAYS and COUNTING
2013-Nov-25
Comet C/2012 S1 (ISON) is now 3 days from its perihelion on Nov 28 UT (Thanksgiving Day). With the comet closing in on the Sun, it is no longer visible for the majority of us. The last visual observations were reported late last week and place the comet between magnitude 3.5 and 4.5 with a long, intricate ion tail.
Now that the comet is invisible to most of us, the monitoring switches over to radio/microwave/millimeter telescopes and Sun-watching spacecraft. Much of the discussion today on the Comets-ml mailing list was about a sharp drop in the rate of production for gas and dust as measured by millimeter wavelength telescopes. Whether this is due to a total disruption of the nucleus or just a slowing down in production is unknown. The next few days will be telling.
In the meantime, there are plenty of online resources that can be used to follow the comet. The NASA Comet ISON Observing Campaign is the best source of up-to-date information on the comet. The NASA STEREO mission team have produced a page that gives the when and where for observing ISON on images taken by STEREO and SOHO. ISON is currently visible in the H1A camera of the STEREO-A spacecraft (latest image here, though the data is initially low-resolution thumbnails, higher resolution images are downlinked a few days later). Starting sometime tomorrow, ISON will also appear in the SOHO LASCO C3 FOV (high-resolution images here).
Also a reminder that C/2013 R1 (Lovejoy) is still going strong and is between magnitude 4.5 and 5.0 in the morning sky south of the handle of the Big Dipper. Though it has not been hyped to the level of ISON, I was able to observe Lovejoy this morning at magnitude 4.7 with a ~1.5 degree long tail in 10×50 binoculars. The comet was even faintly visible to the naked eye.
