There’s a comet in the northern evening sky. Comet PanSTARRS (C/2017 T2) isn’t especially bright yet, but it’s getting there. PanSTARRS was discovered nearly 3 years ago in May 2017 by the Panoramic Survey Telescope and Rapid Response System (PanSTARRS) operated by the Institute for Astronomy at the University of Hawaii. Since its inception in 2006 the survey has discovered more than 200 comets.
Most are too faint for beginning and amateur telescopes, but C/2017 T2 is an exception. Currently glowing at magnitude 9.5 and slowly increasing in brightness, the comet is particularly easy to locate right now as it sails by the Double Cluster in Perseus. Even if you don’t see the comet, the two side-by-side star clusters are a sight to behold in a pair of binoculars or a small telescope.
For a clear look at the comet you’ll need a reasonably dark sky and at least a 6-inch telescope. An 8-inch would be even better. I typically use a 15-inch scope. When I look through the eyepiece at low magnification the comet resembles a fuzzy tadpole with a dense, round head, called a coma, and a short, swept back tail. Photographs show it to best advantage and also reveal the coma’s blue-green color caused by fluorescing carbon atoms and cyanide gas.
The tail is composed of dust released when cometary ices vaporize from solar heating and get pushed back behind the coma by the ever-so-delicate pressure of sunlight itself. Yes, photons — particles of light — exert pressure. Maybe that’s why I feel more relaxed on cloudy days.
Comet PanSTARRS, a distant visitor from the great comet repository in the outer solar system called the Oort Cloud, continues to approach the sun and the Earth. Every day brings it a little bit closer and makes it a little bit brighter. In early May the comet will reach perihelion, when it’s closest to the sun, and brighten to magnitude 8 (or brighter, cross your fingers!) as its slides across the northern sky toward the Bowl of the Big Dipper. An 8th magnitude comet is visible in 50mm or larger binoculars from dark, rural skies and an easy catch in a small telescope.
Now that you know about the comet I invite you to take your telescope out in the next few nights to see if you can find it using the maps provided. It will look like a small, gray fuzzball. Larger telescope owners will observe a tail pointing south. Good luck!
In other news, SpaceX plans to launch another batch of 60 Starlink satellites tomorrow morning, making for a total of 242 in orbit. Barring poor weather the Starlink-3 mission will lift off at 8:06 a.m. CST tomorrow (Jan. 29) from the Cape Canaveral Air Force Station in Florida. You can watch the launch live here. I will also explain how you can see the new flotilla in a blog tomorrow.