Scientists have discovered a rare planet that's around twice the size of Earth and covered by oceans. Featured Image Credit: Flickr / Panther Media GmbH / Alamy Stock Photo Snappily named TOI-733b, it's just one of more than 5,000 exoplanets that we know about after the first was discovered in the 1990s. TOI-733b was found 245 light-years away by NASA's telescope, TESS.