If approved, MIT's TESS satellite would spend two years searching the sky for planets orbiting roughly 2.5 million nearby stars. Image: Teague Soderman (Source: MIT website)

Are we alone in this Immense Universe?  Is Earth The only planet which supports life in this Universe- whose dimensions are beyond comprehension - if not infinite? These are the questions which were haunting the human brain from the time immemorial when he started counting stars. It’s the inner human desire to know are there any of our twins in another part of Universe- are they more advanced than what we are? With advancement of technology the task which once thought impossible and confined to speculation , has got new turns.  Scientists at various institutes like MIT and NASA are coming with new ways to find habitable planets.

The race to find exoplanets( planets beyond our solar system ) continues to quicken. Last week NASA researchers announced that the agency's new space telescope, Kepler, has discovered five new exoplanets , expanding the number of known exoplanets to 422, an increase of about 25 percent in the past year alone.

Kepler will continue science operations until at least November 2012. It will search for planets as small as Earth, including those that orbit stars in a warm habitable zone where liquid water could exist on the surface of the planet. Since transits of planets in the habitable zone of solar-like stars occur about once a year and require three transits for verification, it is expected to take at least three years to locate and verify an Earth-size planet.Launched on March 6, 2009, from Cape Canaveral Air Force Station in Florida, the Kepler mission continuously and simultaneously observes more than 150,000 stars. Kepler's science instrument, or photometer, already has measured hundreds of possible planet signatures that are being analyzed.

Most of the 422 exoplanets discovered to date are hot Jupiters, giant planets that are likely inhospitable to biological activity.If a planet with the right mass is found at the right distance from a star—in the so-called Goldilocks zone, where it is neither too hot nor too cold—most of the work is done. The raw materials for life are common.Water is probably the most common molecule in the universe.The research is based on surveys of stars with gas giant planets—similar to Jupiter and Saturn—that orbit far from their stars.

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As in our solar system, vast distances stretch between these stars and their gas giants. This creates ample room for rocky planets to thrive in the stars' habitable zones, the regions where liquid water can exist.And that boosts the likelihood that other Earths, and maybe even other forms of life, abound in the Milky Way.

But in some star systems it's thought that gas giants migrate inward, knocking any smaller planets out of their orbits or destroying the rocky worlds outright.Meanwhile, star systems like ours have gas giants in stable outer orbits.

"In these systems there is room for terrestrial planets to prosper and not get knocked out of their orbits," said Andy Gould, an astronomer at Ohio State University. What's more, studies of Jupiter suggest that outer gas giants can act as gravitational shields, protecting inner rocky worlds—and any life-forms on them—from frequent asteroid impacts.

To find such star systems, nearly a hundred scientists joined forces as part of the Microlensing Follow-Up Network, or MicroFUN, to scour the galaxy using a technique called gravitational microlensing.

The point that is being researched is stars that are some thousands/hundreds of light years away. It's ofcourse impossible to see them. But how scientists analyse the palnets of these stars which are so far away that even light takes time to travel. This is by a technique called gravitational microlensing (Based on Einstein's "Theory of Relavitiy" that light can be bent from it's path by a massive objesc like star ) . The detail is explained below.

Cosmic Magnifying Glass

In this method, when one star passes in front of another, as seen from Earth, the nearer star's gravity acts like a lens, bending and magnifying the more distant star's light. If the nearer star has orbiting planets, keen-eyed observers can spot the subtle clues of their presence in the magnified light.If all the stars in the Milky Way hosted solar system twins, astronomers should have found at least six such systems them by now, according to a statistical analysis of four years' worth of microlensing data.

"For the first ten years of planet hunting, results are reassuring us that there are solar systems akin to our own. This is real data that strengthens the hypothesis that there are many habitable worlds like our Earth." noted Debra Fischer, an astronomer at San Francisco State University who was not involved in the research.

Scientists also advanced the possibility that our solar system contains hundreds or even thousands more dwarf planets like Pluto, hidden from view in the distant region known as the Kuiper belt. There is a growing body of evidence that the poorly understood region contains several Earth- or Mars-size planets and many tinier bodies, said NASA planetary scientist Alan Stern, adding that this could very well be a "new Copernican revolution" in our understanding of planets.

Based on stasistical data and finding of one star with it's own version of Jupiter and saturn means just 15 percent of the galaxy's stars must have solar systems like ours, Gould(an astronomer at Ohio State University) and colleagues announced this week at the 215th meeting of the American Astronomical Society in Washington, D.C.

MIT Suggests TESS

In addition a satellite is being proposed by MIT researchers that could accelerate these discoveries and even detect hundreds of Earth-sized planets — a few of which could be natural candidates for life.The MIT team, led by Senior Research Scientist George Ricker of the Kavli Institute for Astrophysics and Space Research, is awaiting NASA approval for the Transiting Exoplanet Survey Satellite (TESS), which would conduct the first-ever spaceborne survey of transiting planets, or planets that pass in front of their host stars as seen from Earth. By searching a region of the sky 400 times larger than revealed by Kepler's scope, TESS would observe 2.5 million of the closest and brightest stars when it is launched. Ricker's team predicts it would detect between 1,600 and 2,700 planets within two years, including between 100 and 300 small planets.

"Although TESS should find hundreds of small planets, only a handful would be in the 'habitable zone' and would be natural candidates for life," said MIT assistant professor of physics Joshua Winn, who is part of Ricker's team.

TESS would focus on finding smaller planets similar in size to Earth. Using six wide-angled, high-precision cameras to scan the sky for temporary drops in brightness caused when a planet passes in front of its star, TESS would measure the light obscured by a planet as it transits. TESS would then catalog the light curves caused by these transits so that follow-up work through ground observations and high-resolution spectroscopy can determine the planet's mass, radius and density. Spectroscopic studies with the upcoming James Webb Space Telescope of bright exoplanets found by TESS could reveal details about a planet's atmosphere, such as whether water or carbon dioxide exist.

So this says in brief about the man's inquisitve nature to find aliens. I really wish we find our brothers of distant worlds and pray that our other evil angle of Humans won't make us to go and attack them for resources (ya, I am talking of Avatar Movie ) .........

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