"It popped up out of nowhere," said astronomer Stephen Smartt, who first discovered the new supernova, and promptly named it "cow" according to the alphabetical protocol set by the International Astronomical Union (IAU).
The name might be fortuitous (I mean, we can all imagine astronomers yelling, "holy cow! a new supernova just popped out of nowhere!") but the heavenly event is a big deal in astronomy.
From this Nature news article by Davide Castelvecchi:
At first, Smartt discounted the effect as an unremarkable stellar flare in the Milky Way. But then, he realized that it was probably much farther off, in a galaxy called CGCG 137-068 known to be around 60 megaparsecs (200 million light years) away.
“It was 11 o’clock on a Sunday night, and I said to myself, ‘I better tell everybody about this.’” He sent out an alert through the Astronomer’s Telegram, a service for reporting and commenting on transient astronomical observations.
Immediate follow-ups confirmed that the object was a distant one, and so had to be stupendously bright. (It shone brightly enough that, despite its distance, a number of amateur astronomers were able to see it, too.)
And this was no ordinary supernova: it reached its peak brightness in days, not weeks. "Everybody put down what they were doing up to that point" and started following Cow, says Daniel Perley, an astrophysicist at Liverpool John Moores University, UK.
Initial data suggest that the supernova was caused either by a black hole tearing a star apart or a spinning neutron star.