By contrast, free-floating planets emit virtually no energy and, by definition, they do not orbit a host star.

These planets would also be subjected to the gravitational disruptions of a passing star that could fling the planet away from its life-sustaining host star.

It detects planets that 'transit' or pass in front of their host star, causing periodic dips in its brightness as measured by the telescope's sensitive light detector.

Of the nine planets, two were close enough to their host star to contain liquid water.

Astronomers have inferred their existence from the way they perturb the motion of the host star.