Dual Supernovae Light Up June Nights (Sky&Telescope)
By: Bob King | June 8, 2016
Recent years have seen a blizzard of new supernovae discoveries from dedicated robotic searches by both amateurs and professionals. If you have any doubt, David Bishop's excellent Bright Supernova site lists 3,471 reported in 2015. Already this year, we're up to 2,910!
Sorting through them to find visual candidates takes more time that it used to, but I'm not complaining. Among the ubiquitous 18th- and 19th-magnitude candidates there are always a few bright enough to spot in an 8-inch or larger telescope. On May 28th, two new exploding stars were discovered, SN 2016coj in NGC 4125 (a 10th-magnitude elliptical galaxy in Draco) and SN 2016cok in the bright spiral M66 in Leo, by the automated Lick Observatory Supernova Search (LOSS).
SN 2016coj's initial brightness of ~15.5 magnitude didn't immediately shout "Hey, look at me!" But in recent days, the Type Ia supernova brightened steadily to its present magnitude of 13.6, making it fair game for 10-inch and even 8-inch telescopes.
Several nights back, I took a look at the host galaxy in my 15-inch (37-cm) reflector. Its location near a 6th-magnitude star a short distance north of the Big Dipper's bucket made the finding easy. When I used 142×, the supernova presented itself almost immediately as a "second nucleus" about 11.7? northeast of the true nucleus, a tiny kernel of light buried in the galaxy's core. When the seeing steadied, the supernova stood out crisply, a sharp point compared to the slightly fuzzy galactic nucleus. Here before me eyes was the end of a life, a white dwarf blown to bits in a tremendously powerful explosion brought on by ... weight gain.
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