Wonky signals from distant stars could be sign of exocomets

Aug 24, 2017

By Jesse Emspak

The Kepler space telescope has seen thousands of exoplanets, and now we can perhaps add exocomets to the list. Potential evidence of comets has been found around two stars known as KIC 3542116 and KIC 11084727, both about 800 light years away.

Kepler finds planets by measuring the intensity of a star’s light over time. When a planet passes in front of its host star, an event called a transit, the light dims slightly. The “light curve” – a graph of the star’s brightness over several days – shows a symmetrical shape, with the light levels dropping and then rising again at equal rates.

This symmetry arises because both planets and stars are spherical, but the transits found by Andrew Vanderburg at Harvard University and his colleagues were asymmetrical, meaning that whatever made them was not a sphere. The team turned to comets as a possible culprit, because they release gas and dust from one side, creating long tails that stretch out into space.

“If you have a bunch of dust that you put in space, it will expand quickly outwards, not necessarily be symmetric,” says Vanderburg. You would see a steep dip in the star’s light, followed by an uneven rise.

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