This made the rounds on most of the major media outlets this week so I thought it was worth a mention.
Astronomers have discovered a planet that was formed outside of our Galaxy, but is now within our galaxy.
io9 explains it pretty well:
Before the discovery of this gas giant, it was incredibly rare to find planets orbiting ancient stars – and even more rare to find them orbiting a star like this one because it lacks the necessary metals to form planets. This planet’s star, amazingly, is both old and metal-poor, and what’s more the star has entered its red giant phase, in which it expands to an incredible size and threatens to engulf its planets. That’s what you can see in the rather mind-blowing, somewhat impressionistic artist’s conception up top. That black dot just to the lower right of center is the planet in question.
So this planet is impossible for three reasons, all to do with the extreme conditions of its star.
Just to add to the strangeness, the star should have swallowed up its planet, based on the planet’s position relative to the star. But that’s nothing compared to the story of its birth. This star is part of a group that was once part of a satellite galaxy apart from the Milky Way, which was gravitationally disrupted and assimilated into our galaxy several billion years ago. In all likelihood, this planet predates that merger, meaning it’s technically the first planet we’ve discovered that’s from another galaxy.