Scientists have described a black hole that's nearly 16 times the mass of the Sun. Dubbed M33 X-7, the enormous object is known as a stellar black hole because it formed after the collapse of the core of a massive star. But scientists say M33 X-7 isn't just interesting because of its size. It's part of a binary system, orbiting a star that's 70 times the mass of the Sun. The two are in a tight orbit: the star eclipses M33 X-7 twice per week. Eventually it will go supernova, exploding outwards and collapsing into a second massive black hole.

M33 X-7 was actually discovered in 1981, but the companion star wasn't spotted until 2004, and even then many questions remained. Some thought a neutron star might have been in the mix.

Now we all just have to wait around to see what happens next with this massive, and only slightly less mysterious pair.—Gregory Mone 

Swift is the first satellite explicitly designed to solve the mystery of gamma-ray bursts, the enigmatic explosions that have puzzled astronomers for decades. Practically every day, another burst randomly appears in the sky, flashing powerful gamma rays for anywhere from a fraction of a second to two minutes. Before the burst fades, Swift quickly locates it, rotates its telescopes and other satellites for observation, and relays the burst's location to ground-based telescopes, which study it in detail.