Astronomers have identified a planet in the making.
The variable brightness of GM Cephei — a 4-million-year-old star 870 parsecs away — has been noted for decades. But whether that variability is caused by bursts of light from the star or by an object in the disk of dust that surrounds it has been a matter of debate.
Wen-Ping Chen at the National Central University in Jhongli, Taiwan, and his team argue for the latter. Using telescopes positioned around the world, the researchers monitored GM Cephei from 2009 to 2011 and found that the brightness of the star dipped each year for about a month. The researchers interpret this variability as evidence of a young planet: a clump of dust, roughly the mass of an asteroid, which is orbiting GM Cephei.