An extreme pair of superdense stars orbiting each other has put Einstein's general theory of relativity to its toughest test yet, and the crazy-haired physicist still comes out on top.
About 7,000 light-years from Earth, an exceptionally massive neutron star that spins around 25 times a second is orbited by a compact, white dwarf star. The gravity of this system is so intense that it offers an unprecedented testing ground for theories of gravity.
Scientists know general relativity, proposed by Albert Einstein in 1915, isn't the complete story. While it does very well describing large, massive systems, it's incompatible with quantum mechanics, which governs the physics of the very small. For something extremely small, yet extremely massive -- such as a black hole -- the two theories contradict each other, and scientists are left without a physical description.
