It’s kind of amazing that with nearly 500 planets discovered orbiting other stars, we’re still finding ones that are really weird. Massive planets orbiting so close to their stars they are practically plowing through the stellar atmosphere; hot spots on the planet not aligned with their stars; planets orbiting so far out it’s a struggle to understand how they got there.
And now we can add the planets NN Serpentis c and d to that list.
Lying about 1500 light years from Earth, NN Ser is a binary star — most stars in the sky are part of multiple systems, so that in itself isn’t all that odd. But NN Ser is weird: it’s a very dinky red dwarf orbiting very close to a white dwarf. And by very close, I mean really close: they’re separated by only 600,000 km (360,000 miles), which isn’t much farther apart than the Earth and the Moon!
I’ll get back to the stars in a sec. The planets found (named c and d because the two stars are a and b, according to the naming conventions) are Jupiter-scale beasts, with masses of about 6 and 2 times Jupiter’s, orbiting the binary stars at a distance of roughly 825 and 450 million km (500 million and 270 million miles).
Those numbers don’t seem too odd; lots of planets have been found with similar characteristics. But when you take a closer look at the system…