For astronomers and aficionados of cosmic violence, an obscure star known as V838 Monocerotis has turned out to be a gift that has kept on giving for a long, long time.

The star forms part of the shoulder of an imagined unicorn in the constellation Monoceros, 20,000 light-years away, and in January 2002, astronomers saw it blow up. Over the next few months, it became a million times as luminous as the sun and swelled in diameter to a billion miles, comparable to the orbit of Jupiter. It was briefly one of the most luminous stars in the galaxy.

Astronomers are still arguing and speculating about what happened. Measurements of the star’s light output showed that the explosion happened in three stages, flaring and then dimming three times from January to March 2002.

Some scientists have suggested that V 838 swallowed planets in its orbit. Others have proposed that V 838 was actually two stars orbiting each other, and that the explosions were a result of their atmospheres merging into a common envelope of gas.