The most-watched visitor to our solar system in years is getting closer.
Comet ISON (C/2012 S1), discovered more than a year ago, will make its closest approach to the sun Thanksgiving Day, Nov. 28 (anywhere from just 730,000 miles to around a million miles), which should send it into quite the illuminated state.
ISON has made a perilous journey from the land of comets, also known as the Oort Cloud. This is its inaugural trip around the sun, meaning it is still made of pristine matter from the earliest days of the solar system's formation, allowing scientists a rare opportunity to observe a visiting heralder of history. It's been heading for us for about a million years, and the most dangerous part of its journey will begin once it passes Mercury on Nov. 19.
Observation opportunities are yours for the taking, but special circumstances help immensely. ISON is no Hale-Bopp or Hyakutake, so naked-eye splendor with this one remains to be seen and we probably won't know the extent of ISON's brightness until the end of the month.
Your best shot at seeing ISON is to make your way to a dark location in the wee hours, around 4 a.m. (I know, I know), as far from light pollution as you can manage. You'll need at least binoculars, but a telescope would be ideal. They need not be super powerful - ISON is close enough to be spotted with run-of-the-mill binoculars.
So once you're out in a cold, dark field at 4 a.m. far from New London's lights, look east toward the constellation Leo rising. It looks like a question mark or a sickle paired with a bright triangle of stars closer to the horizon. This week, ISON is creeping along the eastern horizon below that bright triangle, closing in on the border of Virgo.
Gaze upon the triangle (not the sickle) and pick out the brightest star. That star's name is Denebola (Arabic for "tail of the lion"), and it will be your guide to locating ISON for the moment. Train your binoculars or telescope near the triangle of stars and you should notice a soft, glowing fuzzball. It glows because its icy core is melting as it approaches the sun. Its faint tail will be expanding slowly over the coming weeks.
If schlepping a telescope to a remote field at 4 a.m. isn't your thing, there's a good chance the comet will reach naked-eye brightness by mid-November - if it remains intact. Pressure from solar particles and its proximity to the sun's harsh radiation means it may break apart and fizzle into nothingness. Or, a solar flare could take the tail right off.
Let's hope that doesn't happen. Should ISON survive its slingshot around the sun, the December and January sky will readily showcase a very bright and beautiful comet visible to the naked eye and apparent all night long.
Astronomy is full of wonder and disappointment - rare hybrid solar eclipse that was blocked by clouds last Sunday at sunrise, anyone? - so hopefully this astronomical event, with its more leisurely observing time-frame, will reward a satisfying view to anyone who seeks it.