In what is being called a "paradigm shift" in the search for extraterristrial life, scientists announced that they have discovered three rocky planets in the so-called "habitable zone" of a nearby red dwarf star.  The orbit of the planets as well as their distance from the star suggests that the newly discovered worlds could harbor life.

AFP:

The three orbit an ultracool dwarf star a mere 39 light years away, and are likely comparable in size and temperature to Earth and Venus, they reported in a study, published in Nature.

"This is the first opportunity to find chemical traces of life outside our solar system," said lead author Michael Gillon, an astrophysicist at the University of Liege in Belgium.

All three planets had the "winning combination" of being similar in size to Earth, "potentially habitable" and close enough so their atmospheres can be analysed with current technology, he told AFP.

The find opens up a whole new "hunting ground" for habitable planets, he added.

Gillon and colleagues calibrated a 60-centimetre (23.5-inch) telescope in Chile, known as TRAPPIST, to track several dozen dwarf stars neither big nor hot enough to be visible with optical telescopes.

They zeroed in on a particularly promising one -- now known as TRAPPIST-1 -- about one eighth the size of the Sun, and significantly cooler.

Observing it for months, the astronomers noticed that its infrared signal faded slightly at regular intervals, evidence of objects in orbit.

Further analysis confirmed they were exoplanets -- planets revolving around stars outside our solar system.

The innermost two circle their dwarf star every 1.5 and 2.4 days, though they are hit with only four and two times the amount of heat-generating radiation that Earth receives from the Sun.

The more distant orbit of the third planet takes between four and 73 days, according to the study.

"So far, the existence of such 'red worlds' orbiting ultra-cool dwarf stars was purely theoretical, but now we have not just one lonely planet but three," said co-author Emmanuel Jehin, also from the University of Liege.

He called the discovery a "paradigm shift" in the search for life elsewhere in the universe.

Given their size and proximity to their low-intensity star, all three planets may have regions at temperatures within a range suitable for sustaining liquid water and life, the study concluded.

Make no mistake: this is a very significant discovery.  The universe is teeming with these red dwarf stars – far and away the most plentiful kind of star in the Milky Way galaxy and probably others.  Given what we know about planet formation, the odds are pretty good that other planets orbit these cool stars, and if so, the search for E.T. just got a lot bigger.

We await an analysis of the atmosphere of these planets – if they have one.  Mars lost its atmosphere billions of years ago, but at one time, liquid water flowed on the red planet.  And just because any of these planets has an atmosphere doesn't mean there is life present, much less intelligent life.

Discoveries like this await NASA's next-generation space telescope.  Already costing nearly five times its projected budget and six years behind schedule, the $8.3-billion James Webb Space Telescope, originally scheduled for a 2011 launch, will now be deployed sometime in 2018.  It will sit 900,000 miles from Earth in orbit around the sun.  It's supposed to be bigger and better than Hubble, and because it will be beyond contaminating earthlight and face away from sun, in theory, it should be able to image objects as small as an Earth-sized planet.

The universe just got a little smaller.