Comets

Comet ISON: Boom or Bust?

When Comet ISON, or more accurately C/2012 S1 ISON, was first discovered on September 21, 2012 it presented itself in images taken with a 16-inch telescope belonging to the International Scientific Optical Network (ISON). This group is made up of several observatories around the globe specialized in finding asteroids. Comet ISON was found 625 million miles from the Earth (roughly 6.5 times the distance from the Earth to the Sun) and was extremely faint at magnitude +18.

For over a year now since it was discovered it has continued to venture into the inner solar system on course to having a close encounter with the Sun. It will reach perihelion on November 28, 2013, at a distance of only 1.1 million miles from the Sun. By comparison the planet Mercury (the closest planet to the Sun)  can get as close as  28.5 million miles from the Sun. So ISON will get extremely close to the Sun and for all intents and purposes it will be a sun-grazing comet.

Comet ISON on 11/03/2013 taken by FWAS member Ben Hudgens from near Stephenville, TX.

At this posting ISON is currently magnitude +9.5 and only brightened slightly over the month of October. The hope is that trend will change as the comet continues to get closer to the Sun.  If Comet ISON survives its close encounter with the Sun on November 28, 2013, it could emerge glowing extremely bright! In fact there is the possibility that the comet could easily be visible near the Sun in broad daylight. If the comet’s nucleus breaks apart just after perihelion much more material (ice, dust and gas) will be exposed to the intense solar radiation and it will be spread over an even larger area meaning it’s brightness will increase even more. But there is really no way to know or predict what it will do. That in itself is part of the fun and fascination of observing comets. You just never know what the next day may bring. Comets may brighten suddenly or fizzle and fade or they can even break apart into a string of pearls.

Comet Hale-Bopp
Comet Hale-Bopp

Comet ISON has the potential to become a bright and memorable comet such as Comet Hale-Bopp in 1997 but most astronomers thought it would be brighter than it currently is given its location so close to the Sun. Only time will tell. Comet ISON might just have a few tricks up it’s sleeve. So when will be the best time to see the comet? December should be the best time to view comet ISON. The comet will emerge into the morning sky early in the month but by mid-December the comet will then be visible at both dawn and dusk!  It will be visible from the eastern horizon just before sunrise and low in the west soon after sunset. By Christmas the comet will make its closest approach to Earth, Comet ISON will be a circumpolar object. It will stay visible all night, 20° above the northwestern horizon in the early evening and 60° high in the northeast just before dawn. Get ready for a winter/holiday comet display that could be full of surprises.