ScienceShot: Some Young Planets May Be Mirages

Planets emit no light of their own, so observers hunting for worlds orbiting other stars usually detect them indirectly. Now, one such technique has come under fire. The gravity of a planet circling a star in a dusty disk can carve gaps in the disk. But as researchers report online today in Nature, if the disk harbors as much gas as dust, the gas can cause the dust to clump into rings with sharp edges—even in the absence of planets

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