Comet ISON Nears Date With Sun

riverat1 writes "Now visible in the morning sky, comet ISON will swing around the Sun on November 28. ISON will pass 730,000 km above the surface of the Sun at closest approach (Mercury's perihelion distance is 46 million km). If it survives its near brush with the Sun it could provide a spectacular sky show from December into January. This NASA timeline shows that ISON will be the most observed comet ever as instruments ranging from a balloon carried telescope to the Hubble Space Telescope to the STEREO satellites will be brought into play. Lowell Observatory astronomer Matthew Knight lays out three possibilities for ISON: spontaneous disintegration before it gets to the Sun (less than 1% chance); disintegration as it rounds the Sun; or survival. If it survives, its closest approach to Earth will be on December 26 at about 1/3 of an AU."

Re:most observed comet ever

[Zocalo]

It's currently quite visible to the naked eye, if you can get away from any significant light pollution. You'll need to look due East just before dawn for the best views; ISON is currently passing by Spica in the constellation of Virgo [spaceweather.com]. If you've got a reasonable camera that can do manual exposures and a tripod, then you'll get a much more impressive image by using a longer exposure and a mid-telephoto focal length; a 70-200mm range is currently ideal depending on how much of the tail you want to try and capture, or go for a longer length if you just want to capture the quite spectacular coma. Open the lens to the widest aperture, manually focus to infinity (I use a bright star for this), keep the exposure down to about 20s and adjust the ISO to suit.

Re:"Spontaneous"?

[fatphil]

The centre of mass of the fragments will continue in the same path initially. However, the smaller the fragment, the more the solar wind will affect it. Some groups of comets that appear at about to have a very similar path have been conjectured to be just components of much larger comets that have fragmented (e.g. the Kreutz group).