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     Volume 8 Issue 63 | March 27, 2009 |

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In Search of Celestial Neighbours

Obaidur Rahman
The Kepler Space Craftin space.

Remember that famous “I Want to Believe” poster of an Alien Spacecraft on Fox Mulder's office in the famed T.V series “The X-Files”? The classic question of “Are we alone in this universe” has fascinated us for generations and all the mystery that shrouds in the possibility of life on other planets has simply fueled our curiosity in extra-terrestrial existence. As an effort to find definitive answers to this question which is old as time itself that whether Earth is unique or there are others like it out there, NASA, on March 6 2009, has launched the Kepler Spacecraft from the Cape Canaveral Air Force Station, Florida; the mission objective is to discover Earth like planets orbiting other stars. This 600 million dollar project is not just a scientific mission but a historic one as well because for the next 3.5 years Kepler will observe over 100,000 stars around Cygnus and Lyra constellations of the Milky Way and identify the true Earth analogs that is Earth-sized planets orbiting stars like that of our good old Sun at distances where surface water and hence life could certainly exist. This mission is of great significance for the human race because according to William Borucki's words, the mission's principle science investigator, “Even if we find no planet like Earth that by itself would be profound. It would indicate that we are probably alone in the galaxy.”

The size of the known universe is spectacularly and inconceivably vast.

In fact, there are more planets out there than all the sand grains combined in all the beaches of Earth! That is indeed quite a number and the universe that houses them is “mindbogglingly big” as the movie “The hitchhikers guide to the Galaxy” neatly puts it. It was the ancient belief that Earth was the centre of the universe but it is now scientifically acknowledged that Earth isn't even at the centre of the solar system. In fact the solar system is not even at the centre of our galaxy and our galaxy is no way in any special position in contrast to the rest of the known universe. So, from an astronomical viewpoint, Earth is not enjoying any privileged position in space. So the idea that life would only thrive on Earth and nowhere else doesn't sound very convincing. If there are other beings, whether their civilization is advanced as ours or more so is a matter of superior research which Kepler Mission is aiming to perform.

Armed with the largest camera ever launched into space, a 95 megapixel array of charge-coupled devices (or CCD's, like the ones in ordinary digital cameras) with a 12 degree diameter Field Of View, Kepler is the world's first mission with the ability to find true “habitable zones” in the space as it is specially designed to survey the extended solar neighbourhood to detect and characterise hundreds of terrestrials and larger planets in or near the habbitable zone which will broaden the understanding of planetary formation, the frequency of formation, the structure of individual planetary systems and the generic characteristics of stars with terrestrial planets. The first planets that are expected to be exposed to Kepler's “radar” are portly “hot Jupiters” which are basically gas giants (a large, massive, low-density planet composed primarily of hydrogen, helium, methane, and ammonia in either gaseous or liquid state), that circle close and fast around their stars followed by Neptune size planets and then rocky ones like that of Earth. As the mission progresses Kepler will drift farther and farther behind Earth in its orbit around the sun in search for true Earth analogs, planets with surface water and possibly life!

The scientific objective of the Kepler Mission is to explore the structure and diversity of the extrasolar planetary systems. This is going to be achieved by surveying a large sample of stars to:
* Determine the frequency of terrestrial and larger planets in or near the habitable zone of a wide variety of spectral types of stars.
* Determine the distributions of sizes and orbital semi-major axes of these planets
* Estimate the frequency of planets and orbital distribution of planets in multiple-stellar systems.
* Determine the distributions of semi-major axis, albedo, size, mass and density of short-period giant planets.
* Identify additional members of each photo-metrically discovered planetary system using complementary techniques.
* Determine the properties of those stars that harbor planetary systems.
Source: http://kepler.nasa.gov

The chance of the Kepler Mission to detect Earth-like planets is much higher than the Hubble Space Telescope because in contrast to the latter one, Kepler has the ability to observe over 100,000 stars simuntaneously while measuring variations in their brightness every thirty minutes. Besides, there is a strong astronomical probability that if 100% of stars studied by Kepler out there had the exact same diameter as the Sun and each had one Earth-like terrestrial planet in an orbit identical to that of the Earth, then Kepler would find about 465 of them. Scientists also expect that since Kepler, which is an Earth-trailing solar orbit, is pointing in the direction of the Solar System's motion around the centre of the galaxy, the stars that are going to be observed by Kepler are roughly the same distance from the galaxy centre as the solar system. This fact is very crucial because it will usher the better understanding on whether the position in the galaxy is related to habitability which is suggested by the Rare Earth Hypothesis, which states that Earth-like life is rare in the Universe while microbial life is common. Here it is important to mention that on August 7 1996, NASA scientists profoundly announced to the world that within a Martian meteorite, they had found evidence of a microscopic life form that may have existed on Mars more than three billion years ago. However in the global astronomical community this claim is still a matter of debate.

Astro-biologically speaking, there are many arguments on what extraterrestrail life would be like. There are some who believe that all life is like life on Earth that is carbon-based lifeforms while there are others who believe silicon and even ammonia-based lifeforms could exist in other planets. There are two accepted hypothesis regarding the origin of extraterrestrial life one of which proposes that it may have emerged independently from different places in the universe while the alternative one, the panspermia hypothesis, says that life emerges from one specific location and then spreads between habitable planets. According to Hubble Space Telescope's observations, there are at least 125 billion galaxies in the universe, at least 10% of all sun-like stars have a system of planets and there are billions of stars with planets orbiting them in the universe. And even a billionth of these stars have planets that support life then there are around 6.25 billion life-supporting solar systems in the universe. So far scientists strongly believe that the following planets have once developed or presently continue to host life and these include Venus, Mars, Mercury, moons of Jupiter and Saturn (e.g. Europa, Enceladus and Titan), Gliese 581 c and d. Kepler's finding will eventually strengthen more of these scientific assumptions.

Somebody once said the story of the universe is the story of each of us and Kepler's active effort to determine if any other planet harbours life, perhaps with civilizations more advanced than ours, will only help us understanding ourselves better. Whatever the findings may be of Kepler it will definitely make way for future journeys that will usher betterment for mankind and aid us in realising how insignificant yet terrifically crucial our existence is in the whole wide universe. Believe or reject, scrutinise or criticise but as the saying goes, there is more than what meets the eye, surely “Truth is out there”.


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