Mapping the cosmos as we see it from Earth is a never-ending job, but one of the nice things about stars is that they tend to hang around for quite a while. That’s why when, in 1437, Korean astronomers first spotted a new star in a familiar constellation they were puzzled, but prepared to accept it as yet another feature of the night sky. Then, two weeks later, it was gone.

A newly discovered star completely disappearing into the blackness of space isn’t something happens every day — or hardly ever, really. Stars don’t just appear and then vanish in the span of 14 days, but that’s exactly what seemed to happen, and it’s taken centuries to figure out why. As it turns out, the star didn’t appear and vanish at all, it was simply blowing off some steam.

The research, which was published this week in the journal Nature, was led by Dr. Michael Shara of the American Museum of Natural History, and has a ironclad explanation for why the star was behaving so oddly.

Scientists now believe that the star in question was actually a white dwarf. Not normally visible in the night sky due to it being “burnt out,” what is left behind remains hot and has some serious gravitational pull. That pull draws in hydrogen from a neighboring star, and that material continues to collect for untold eons until the pressure is so great that it detonates. The explosion, called a nova, is incredibly bright and allowed the star to be seen all the way from Earth.

Once the the massive explosion concludes, the star goes dark once more, which seems to be what the astronomers in Korea observed many centuries ago.

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