A star has gone missing.
Not in our own Milky Way, but in a galaxy about 75 million light-years away. The star in question is so hot that it glows crystal blue, and it shines a couple million times brighter than the star we know best, our sun. Even as stars go, it’s massive. Astronomers have studied it for nearly two decades, so it was pretty disconcerting when, one day last year, they looked at the latest observations and realized they couldn’t find it anymore.
Andrew Allan, a doctoral student in astrophysics at Trinity College Dublin, checked and rechecked the data. The star is too far away for telescopes to spot it directly, so astronomers look for the distinct signatures that these luminous blue stars imprint on the light coming from their home galaxy. But those traces had vanished.
Maybe, Allan thought, this was Earth’s fault. The weather hadn’t been great on the day that the telescope, perched in the mountains of northern Chile, had examined the distant galaxy. So he and his colleagues decided to conduct another round of observations on a different instrument at the observatory a few months later. Once again, no star.
“It was a pleasant surprise for us,” Allan told me.
Pleasant? When I asked Allan about this discovery, which was announced yesterday, I had expected some alarm in his response, maybe even a hint of panic, over an apparent cosmic disappearance. Outer space certainly can be a mysterious and surprising realm, but stars like this one aren’t supposed to blink out without a trace. They usually finish their life in a powerful, radiant explosion—a supernova—leaving behind a newly formed black hole.