Dwarf planets compared

Solar System

Dwarf Planet 2007 OR10: Big, Dark, and Slow

A Kuiper Belt object discovered nearly a decade ago turns out to be much darker — and thus larger — than thought. It's also an especially slow spinner.

artist's impression of a black hole

Black Holes

Astronomers Gauge Spin in Black Hole Duo

Astronomers have measured the spin of one of the universe's most massive black holes — and provided evidence that the behemoth has a companion.

Black Holes

Setting Limits to Black Hole Gluttony

Black holes may have a limit to how much they can eat in the public eye.