Billion planets

That planets can be found at the centre of the galaxy, as well as near our solar system, has given NASA researchers confidence that they are likely to be everywhere. And if that8217;s the case, then the likelihood of other Earth-like planets becomes greater. 8220;We all are dreamers, and part of that dream is to find life somewhere,8221; said Mario Livio, head of the science programme at the Space Telescope Science Institute in Baltimore, which oversees Hubble operations. 8220;We8217;re finding that the galaxy is full of planets and the chances are, somewhere out there, we will find one with the conditions necessary to be habitable.8221;

The new planets were introduced on Wednesday as mostly 8220;candidates8221;, since only two could be definitively described as planets. But Livio and team leader Kailash Sahu said the chances were high that some, or even all, of the 16 will ultimately meet all the criteria to be called planets.

Based on the number of planets identified and the number of stars in the Milky Way, the scientists estimated that as many as 6 billion Jupiter-size planets exist in the galaxy. 8220;Our discovery 8230; gives very strong evidence that planets are as abundant in other parts of the galaxy as they are in our solar neighborhood,8221; Sahu said.

One of the biggest surprises of their work, Sahu said, was that five of the likely planets orbit so close to their suns that they make it around in less than one Earth day. These close-in, Jupiter-sized planets are not necessarily the most prevalent, they said, but rather are the ones most easily identified using the techniques available now for peering deep into the galaxy. The planet closest to its star has an inhospitable estimated surface temperature of 3,000 degrees Fahrenheit.

The search for what are called 8220;extrasolar8217;8217; planets is done through indirection, since they cannot actually be seen by even the strongest telescopes. Instead, astronomers identify them by the way they briefly block some of the light from distant stars, an event called a 8220;transit8217;8217;. The planet would have to be about the size of Jupiter to block enough starlight to be detected by Hubble.

The Sagittarius Window Eclipsing Extrasolar Planet Search SWEEPS used the Hubble8217;s deep-field telescope for seven days in early 2004. The telescope monitored 180,000 stars in the crowed central bulge of the Milky Way for the periodic dimming caused by planet transits. The area examined by the orbiting telescope is some 26,000 light-years away.

While astronomers detect faraway planets by finding solar transits, they measure and confirm the planet8217;s status by analyzing the slight wobble in a star8217;s motion that occurs when a planet orbits. The 16 planet 8220;candidates8221; introduced on Wednesday were generally too far away and too faint to detect solar wobble, which is why they remained planetary candidates rather than confirmed planets.

NASA8217;s James Webb Space Telescope, which is scheduled to be launched into orbit in 2013, is expected to have the power to make the confirmations.

The SWEEPS results were published in Thursday8217;s issue of the journal Nature.

The Hubble telescope, a joint project of NASA and the European Space Agency, has revolutionised astronomy but is now in dire need of a servicing mission to install two new instruments as well as fresh batteries and gyroscopes.

NASA initially proposed a robotic repair, but the National Academy of Sciences recommended in 2004 that a manned shuttle mission be sent to do the work. NASA Administrator Michael Griffin has said that he will formally review the options later this month, and that he hopes to make a decision soon.

8212;The Washington Post / Marc Kaufman