NLTT 43806 is a white dwarf, the dying remnants of a star like our own. But there's a problem. Its composition doesn't make any sense...unless there was a cataclysm just like the one Earth experienced four billion years ago.
Located about fifty light-years away, NLTT 43806 is unlike any other white dwarf we've seen before. Its aluminum content is abnormally high relative to the amount of iron. On all other white dwarfs we've seen, iron generally outnumbers aluminum by a factor of about ten to one, due to the vagaries of the chemical reactions that go on within the star.
Where you can find a lot of aluminum is in the crust of rocky planets like Earth. After oxygen and silicon, aluminum is the most abundant element in Earth's crust. If you want to find iron, you need https://publish.io9.com/ged/new#to go in deeper, as the core is where most of our planet's iron is found.
And it isn't just iron and aluminum - a total of nine elements identified on the white dwarf are found in abundance levels that don't make much sense for a star, but fit neatly with what you'd expect on the top layers of a rocky planet. This suggests that NLTT 43806 has at least one rocky planet...but it probably once had an extra. These two planets collided into each other, ripping off huge portions of the crust and upper mantle of the planets.
That collision probably was a lot like the one between Earth and a Mars-sized object, commonly known as Theia. This ancient impact - which we've been talking about a lot lately - was responsible for creating Earth's Moon. So then, NLTT 43806 might not just have a planet - it might also have a large, newly formed moon in orbit around that planet.