Spy Two Supernovae in June’s Night Sky

After millions of years, their light is finally bright enough to see from Earth

Supernova SN 2016cok
The supernova designated SN 2016cok can be spotted at the edge of the Messier 66 galaxy, marked by the two rectangular crosshairs. Gianluca Masi, The Virtual Telescope Project

Supernovae are certainly among the most dramatic cosmic events astronomers may witness, but they aren't particularly rare to spot with the right equipment. By some counts, scientists have already witnessed 2,910 of these exploding stars so far in 2016, Bob King reports for Sky & Telescope. But once in awhile, a supernova occurs close enough to the Earth to be seen without having access to an observatory. And right now, amateur astronomers have two to choose from.

Recently, two different supernovae were spotted in the night skies that are both close enough and bright enough to be spotted with a basic telescope: one in the galaxy NGC 4125 located in constellation Draco named “SN 2016coj” and another lurking in Leo called “SN 2016cok."

Since the two supernovae were first spotted on May 28, SN 2016coj has continued to brighten as more light from the star's detonation millions of years ago finally reached Earth. First seen by the Katzman Automatic Imaging Telescope (KAIT) at the Lick Observatory near San Jose, California, this supernova didn’t initially seem particularly special. Over the course of several days, however, it continued to brighten until it appeared nearly as bright as its galaxy’s core, King reports.

SN 2016coj is a Type Ia supernova, which means it was once a white dwarf star that siphoned matter like a vampire from its companion star. But overtime it became too heavy to sustain itself and detonated in a massive explosion.

While the second supernova may be a bit more elusive for the amateur astronomer, it has an intriguing story. Its home galaxy of Messier 66 has long been a favorite target for stargazers and sometimes can even be seen in the same field of view as another nearby galaxy, Messier 65, Bruce McClure reports for EarthSky.org. But SN 2016cok is dimmer and harder to make out in the depths of space than SN 2016coj.

SN 2016cok was spotted by the All-Sky Survey Automated Survey for Supernovae (ASAS-SN). Astronomers studying the spectrum of the explosion's glow have determined that it is a Type IIp supernova. This means that it was once a supergiant star that collapsed under its own weight. This particular type of supernova doesn't steadily decline in brightness, but has several "plateaus" or pauses in the decay, writes King.

The galaxy that houses SN 2016cok is well-known among supernova hunters. Since 1973, five different supernovae have been spotted inside Messier 66, making it a favorite spot to watch for exploding stars, Gianluca Masi writes for the Virtual Telescope Project. With a sharp eye trained at the galaxy, you might be able to pick out this one, too.

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