Two Stars Orbiting Each Other So Closely They Could Fit Inside the Sun
Astronomers have discovered a brown dwarf orbiting a low-mass star so closely that you could fit both stars and their entire orbit inside the Sun. The brown dwarf takes only 1.9 hours to orbit the star, dimming its light each time. It's believed that the two stars were once much farther apart and have shrunk their orbit by a factor of 5 since their formation.
http://arxiv.org/abs/2307.15729
@shnuboops One is already a red dwarf.