We've been seeing some weird stuff happening in deep space recently. First, the supermassive black hole at the center of the Milky Way lit up for some unknown reason, and now NASA says they've detected mysterious green and blue blobs of light that appeared near the center of the "Fireworks galaxy" and disappeared just as quickly. If aliens are having space-raves and I wasn't invited, I'm going to be upset.
According to a new study published in the Astrophysical Journal, NASA's NuSTAR X-ray Observatory was observing a supernova in the Fireworks galaxy when the green blob showed up. The mysterious blob is known as a ultraluminous X-ray source (ULX) and wasn't there the first time astronomers looked at the galaxy, but showed up on their second observation 10 days later. Another NASA telescope, the Chandra X-ray Observatory, then tried to catch a glimpse of the object—now referred to as ULX-4—but found that it had already disappeared. Which is weird.
Hannah Earnshaw, a postdoctoral researcher at Caltech and lead author on the study, explains:
"Ten days is a really short amount of time for such a bright object to appear. Usually with NuSTAR, we observe more gradual changes over time, and we don't often observe a source multiple times in quick succession. In this instance, we were fortunate to catch a source changing extremely quickly, which is very exciting."
There are a few possible explanations for ULX-4, but no one knows for sure. It's possible that astronomers witnessed the very quick annihilation of a star by a black hole. That's also one of the explanations for why our own galactic center lit up recently. As objects are devoured by black holes, their matter gets churned up and spun into the surrounding accretion disks. As the objects are chewed up they get super-heated and radiate X-rays, which then show up to us as undignified green and blue blobs. Usually, though, they last a lot longer.
Another explanation is the always weird neutron star. Neutron stars, perhaps the least understood celestial object, are created when a star isn't quite big enough to make a black hole. Instead it compresses into a very strange ball of neutrons roughly the size of a large city with incredible gravity and a strong magnetic field. The magnetic field of neutron stars form two columns at either pole of the star which blast streams of X-rays out into space. It's possible that what NuSTAR saw was one of the poles of a neutron star briefly pointing at Earth.
It seems like whatever caused these strange space lights is probably one of the weirdest objects we know of. It's pretty cool that a chance observation resulted in some (hopefully) useful data on these strange beasts. Hannah Earnshaw says:
"This result is a step towards understanding some of the rarer and more extreme cases in which matter accretes onto black holes or neutron stars."
It could also be space-raves, which are themselves rare and extreme events.