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 Some of us are very much familiar with the basic requirement for an exoplanet to be counted as habitable: it must reside in the habitable zone of its star. The star should favorably be in the same class as our sun in the main sequence although studies show that red dwarfs could host them as well. As such, much focus is given to searching and filing a catalogue for these types of stars. Enter the HabCat, or the Catalog of Nearby Habitable Systems, a list of about 17,129 stars made by astronomers Margaret Turnbull and Jill Tarter in 2002.
This list came from a much longer list of stars generated by the Hipparcos mission from 1989 to 1993 which took astronometric observations from 118,000 stars with the results published in 1997. Turnbill and Tarter studied this long list of stars to come up with the HabCat, a list of stars that are believed to possess characteristics suitable for life to inhabit the “goldilocks zone” of its planetary systems. It was further narrowed down to the nearest 5,000 stars closest to us in about a 100 light year distance. Turnbull moved on further to identify ten stars in 2006 that have a better likelihood of hosting habitable planets.
Tags: habitable, star, exoplanet
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 Almost nine months after Kepler space telescope launched to space, scientists reveal the first five extrasolar planets discoveries that hopes to inspire us that habitable exoplanets are indeed on the way. Although these exoplanets were not really the type that Kepler was created for to detect, the success of finding them proves that scientists are finally on the verge of nailing the first habitable exoplanet.
Kepler, the so called planet-hunter, was launched in March 7, 2009 after several delays due to NASA budget cuts. Its mission is to find any earth-size exoplanet that lie within the habitable zone of stars, the well-known Goldilocks planet. Unlike the Hubble space telescope, Kepler's gears were fine tuned to detect smaller planets and possess a wider field of view for detecting planetary transits, an event where an exoplanet passes in front of its star. Kepler, however, has the opportunity to observe it a couple of times more than Hubble. In this way it observes the the degree of reduction of brightness of the star from whence the diameter of the exoplanet is derived.
Tags: habitable, star, exoplanet
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 News spread recently about a super-earth sized planet that has been recently discovered to contain one of the most essential compounds for life to exist in the universe, water. With a mass of approximately five to ten times that of earth, GJ 1214b is one of the three exoplanets to have been detected and classified as a super earth by MEarth, a group of astronomers searching for earthlike planets. Most extrasolar planets that have been discovered in the past were huge and hot Jupiter-like gas giants while some were seen as frozen inhospitable planets.
GJ1214b, a massive planet that can house about six earths, orbits a red dwarf at a distance of 1/40th the span between Mercury and our sun and is about forty light years away from us. While some would dismiss the findings and wave off GJ1214b because of the abnormally close orbit with its parent star, we see a different picture and we are inclined to agree with what the scientists have to say. First, the star is a red dwarf, and is significantly more than three hundred times less luminous than our own. Second, scientists believe that its thick atmosphere allows liquid water to exist due to the pressure exerted on the planet’s surface. Third, the observations and smart conjectures are convincing enough such that the presence of water itself on the planet immediately opens up a million of possibilities. Wasn’t there a saying back in school that says “water is a universal solvent”? We use water in our everyday lives and of course, our bodies are mostly made up of water. There is apparently no reason why humans cannot survive there. Before you know it there will be casino resort hotels welcoming the first human visitors to the planet! How many people would have believed humans could walk on the moon, before it first happened? The future is the final frontier. Space exploration is always full of surprises and adventures.
Tags: habitable, star, exoplanet
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 The Alpha Centauri system is perhaps the first destination of a human space mission if present technology will accelerate to the point of developing ships capable of going close to the speed of light. In futuristic space science fiction, Alpha Centauri almost always becomes the first "port of call" or the human's "gateway" to the stars. Understandably, the star system is after all the closest to Earth at about 1.34 parsecs (4.37 light years). The Goldilocks Mission may choose Alpha Centauri as its first destination given that scientists in the last decades have come up with convincing calculations that a terrestrial planetary system may exist within the binary star's habitable zone.
That's right, Alpha Centauri is a binary star system consisting of two stars, α Cen A and α Cen B orbiting a common center of gravity. The larger yellowish-white star, α Cen A, is a brighter solar analog with a mass that is 10% greater than the Sun's. Its companion star, the yellow-orange α Cen B, is a smaller solar analog that has a mass 90% that of the sun. The two stars are 23.7 AUs apart (average) but with their elliptical paths, the minimum distance is at 11.4 AU and the farthest at 36 AU, an orbit that is completed every 80 years. Because of this, the brightness of the stars differ with their positions in the sky when viewed from an possible exoplanet within the system. Both the elliptical orbit and the resulting brightness observation does not have significant effects on the habitability of the planet. In fact, when the stars are at their nearest, the distance between them is at least 2 AUs greater than the mean distance of Saturn from the sun. At their farthest, the separation is at 6 AUs greater than the mean orbital distance of Neptune.
Tags: habitable, star, exoplanet
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