Westlake: Comet Catalina’s pre-dawn performance
November 23, 2015
Comet Catalina was discovered more than two years ago, on Halloween night, 2013, by the Catalina Sky Survey telescope near Tucson, Arizona. This telescope scans the heavens, night after night, searching for NEOs (near Earth objects) and PHAs (potentially hazardous asteroids). Its mission is to find and track all asteroids larger than one kilometer in diameter that potentially could impact Earth. In the process, the Catalina telescope discovers many other interesting objects, including distant comets.
Formally named C/2013 US10, Comet Catalina comes to us from the distant Oort comet cloud that surrounds our solar system. Several million years ago, some unknown disturbance, such as a passing star, nudged C/2013 US10 into a trajectory that would take it into the inner solar system for the first time. Falling sunward for a million years, it made its closest approach to the Sun, called perihelion Nov. 15, traveling more than 100,000 miles per hour.
The comet is now on its outbound journey and will enter our predawn sky this week. Under ideal dark-sky conditions, Comet Catalina could become faintly visible to the unaided eye in December and early January and be easy to pick up with ordinary binoculars. It will make its closest pass by the Earth Jan. 12 at a distance of 66.9-million miles.
During the last week of November and into early December, Comet Catalina will emerge from the Sun's glare and appear a little higher in our predawn sky with each passing day. It will make several noteworthy passes by other well-known celestial objects in the weeks ahead, making it easy to locate. Here's a listing of some of the best upcoming events:
• 5:30 to 6 a.m. Dec. 7 — Comet Catalina will appear about four degrees to the right of the dazzling Morning Star, Venus, and the slender crescent moon. The moon will be hovering only one degree above Venus. Use binoculars to scan for the comet and its wispy tail.
• 5 to 6 a.m. Jan. 1 — Comet Catalina will appear only one-half degree above the bright star Arcturus before dawn. To locate Arcturus and the comet, find the Big Dipper hanging high in the northeastern sky and follow the "arc" of the handle around to the bright star Arcturus. Use binoculars to enhance the view.
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• 3 to 5 a.m. Jan. 15 — Rising before midnight now, Comet Catalina appears only one degree to the lower left of the star Alkaid, at the end of the Big Dipper's handle. It will be highest and easiest to spot just before dawn.
• 10 p.m. to 5 a.m. Jan. 16 and 17 — Comet Catalina appears about 3.4 degrees to the lower left of the famous double star Mizar and Alcor, at the crook in the Big Dipper's handle. You can spot it as early as 10 p.m. on the night of the 16th, low in the northeastern sky, but it will appear much higher in the sky before dawn on the 17th.
No one knows how bright Comet Catalina will become or how long its tail might grow in the coming weeks. That's one of the most intriguing characteristics of a comet: unpredictability.
One thing is certain — Comet Catalina will never this way return. Its recent slingshot around the Sun gave it enough energy to escape the solar system altogether and become an interstellar traveler, destined to wander the Milky Way galaxy forever.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Check out Jimmy's new "2016 Cosmic Calendar" of sky events on his website at jwestlake.com. It features 12 of his best sky photos and a day-by day listing of cool celestial events that you and your family can enjoy watching in 2016.