Bright explosion on Comet C/2012 X1 – an update plus maps to help you find it

An expanding bright cloud of sunlit dust and ice particles surrounds the hidden core of comet C/2012 X1. Fresh icy materials from a large-scale event on Comet C/2012 X1 exposed to sunlight for the first time caused the comet to leap in brightness a few days ago. Photo taken today Oct. 25 by Gianluca Masi of Ceccano, Italy.

Finally got a chance to see the exploding comet C/2012 X1 (LINEAR) from my home this morning through a 10-inch telescope. You’ll recall this is the comet that went from 14th magnitude obscurity straight to binocular brightness without passing Go. The comet’s located in the dim constellation Coma Berenices not far from the handle of the Big Dipper. To see it you have to get up about two hours before sunrise and have a clear view of the northeastern sky. Even at start of dawn, X1 is only about 15 degrees or a “fist and a half” above the horizon.

Wide view of the eastern sky shortly before the start of dawn, Comet C/2012 X1 is low in the northeast near the star Beta in Coma Berenices. Position shown for Oct. 26 at dawn. See detailed chart below for use with telescopes and binoculars. Maps made with Stellarium

I was excited by what I saw. Italian amateur astronomer Gianluca Masi’s photo captures its low-power telescopic appearance well. To my eye the comet was a bright, dense, hazy ball of magnitude 7.5 with a compact knot of brighter material at its center. I could kick myself for forgetting to check it out in binoculars – even in last quarter moonlight I suspect the comet was bright enough to spot in 50mm and larger glasses.

Map covering a 5-degree chunk of sky showing C/2012 X1’s position on Oct. 26 (6 a.m. CDT) through Oct. 30. Use Beta in Coma Berenices to navigate to the comet.  Stars shown to mag. 9.5.

Now the wait is on. Once the moon gets whittled down to a crescent and becomes less of a glare bomb, we’ll soon see how well it may show in small telescopes. I encourage you to watch how the comet evolves in the coming weeks. It’s already brighter than when first seen in outburst on Oct. 21 and continues to expand. I estimated its size at 4-5 arc minutes or about 1/6 the size of the full moon. It’s amazing to see a comet this bright at the remote distance of 279 million miles.

Comet 17P/Holmes underwent a similar outburst in the fall of 2007 but brightened even more. This photo was taken on Nov. 27, 2007 a little more than a month after the explosion. Holmes remained visible for months after its outburst. Credit: Michael Jaeger

Don’t you love it? With all eyes focused on Comet ISON, here comes this upstart from deep space wanting to share a bit of the limelight. While it’s possible the comet was struck by a meteoroid, exposing fresh ices to fizz and broil in sunlight, a more likely cause for the outburst is heated gas beneath the surface breaking through and exposing fresh ice. Solar heating converts the ice directly to gas in a process called sublimation forming a tenuous glowing globe around the comet’s nucleus called a coma.

Watch this blog for more updates and finder maps for the comet in the coming weeks.

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