Over the past few years, other astronomy teams have found evidence of other still-forming baby planets, but this object may be the youngest yet. "The other planets are a little older," says Sascha Quanz, an astronomer at ETH Zurich in Switzerland who led the discovery, in a phone interview.

Using the European Southern Observatory's Very Large Telescope in Chile, Quanz directly observed a planet still in the midst of a disk of gas and dust that surrounds its central star, HD 100546, located 335 light-years away from Earth. The planet hasn't had the time to gather enough mass to clear the dust around it. The other probable protoplanets, discovered in 2011 and 2012, are a step ahead. "They have already cleared a big gap in the disk of their host stars," Quanz says.