NGC 6811 In the star cluster NGC 6811, astronomers have found two planets smaller than Neptune orbiting Sun-like stars.
NGC 6811 In the star cluster NGC 6811, astronomers have found two planets smaller than Neptune orbiting Sun-like stars.
Credit: Michael Bachofner

In May, NASA scientists announced that the space-based Kepler telescope that has been scouring the sky for habitable worlds was in trouble. Part of the mechanism used to position the telescope had failed. Scientists were quick to praise the mission and note that even if it were over, they had more than enough data to analyze. The latest discovery from the data beamed back by Kepler came Wednesday, with the detection of two planets smaller than Neptune orbiting stars in a cluster about 3,000 light-years away.

The find, made by a team led by a scientist from the Harvard-Smithsonian Center for Astrophysics, was remarkable because star clusters can be inhospitable places for planets to form, and few planets had been found in clusters—of 850 known, only four are in clusters. Most surround stars like our sun that are not bunched together with other stars. In an essay accompanying the paper, published in the journal Nature, astronomer William F. Welsh, who was not involved in the study, painted a vivid portrait of the harsh conditions the planets would have had to withstand.

“The stars in a cluster are all kin, born from the same parent molecular cloud—a huge mass of cold gas and microscopic grains teetering on the brink of instability,” Welsh wrote. “A cluster can be far from a placid environment for planet formation.”

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The planets were detected as they crossed between Kepler and their suns, causing a slight dimming of the star’s light.