Extrasolar planets discovered

New planets have been discovered in our galaxy by Nasa's Hubble telescope.

The 16 extrasolar planets are orbiting a variety of distant stars in the central region of the Milky Way and were discovered as part of Hubble's deepest search into the galaxy.

Published in today's edition of the Nature journal, the study analysed the crowded central bulge at the centre of the galaxy, which measures one-quarter the diameter of the Milky Way's spiral disc.

As Hubble's view was limited to a size no bigger than two per cent of the area of the whole moon, the scientists estimated that there could be approximately six billion Jupiter-sized planets in the entire Milky Way.

Five of the newly-discovered planets are unlike any others found in nearby searches. Known as ultra-short-period planets (USPPs), they orbit their stars in less than one Earth day.

The USPP with the shortest orbit, Sweeps-10, whirls around its star in just ten hours and is among the hottest planets ever discovered.

"Discovering the very short-period planets was a big surprise. Our discovery also gives very strong evidence that planets are as abundant in other parts of the galaxy as they are in our solar neighbourhood," said the project's leader Kailash Sahu of the Space Telescope Science Institute, Baltimore.

The findings provide a sounds basis for a study that it is to be carried out from 2008 by Nasa's Kepler mission, which will monitor a region of the Milky Way to detect planets around distant stars.