NASA’s Kepler Mission And New Habitable Planets


The Kepler mission is to scan a small portion of the Milky Way Galaxy looking for planets to determine the percentage of stars that have habitable planets.  It has the ability to detect Earth size planets or smaller and is also able to determine whether or not the planets are located in the habitable zone.  The Kepler Space Telescope uses the transit method to detect planets, which monitors the drop of brightness of a star as a planet passes in front of it.  This is a newer technique of detection, with the majority of planets being detected through the radial velocity method.   What Kepler is able to do that other telescopes can’t do is sit in space and monitor 150,000 stars continuously for over 3.5 years.  So far, Kepler has 2,326 planet candidates with a confirmed 28 planets discovered.

Most recently, Kepler has confirmed it’s first planet in the habitable zone of a Sun-like star.  At 2.4 times the size of the Earth, no one is quite sure whether it is a rocky, oceanic, or gaseous planet.   With a planet this big, if it has a similar composition to Earth, would have a gravity 2.4 times our own.  However, if it was completely made of water it would only have a gravity of 0.43 of Earth, so it might be possible to find comfortable gravity here if the density of the planet was just right.   It’s thought that the temperature could range from a chilly –11 C to a perfect 72 F depending on the strength of the greenhouse effect.  This planet is known as Kepler-22b and is the first of 48 candidates found in the habitable zone to be confirmed.  At 578 light years from Earth, it’s not likely that we will be visiting it anytime soon but it is a step in the right direction so that we can study planet habitability.  It is significant that Kepler-22b orbits a yellow star similar to our own Sun, unlike most other habitable zone planets which have been found orbiting red-dwarf type stars. 

Kepler is finding more and more Earth sized planets as it progresses into it’s mission, because smaller planets benefit from the additional yearly transits especially if they have long orbital periods.  Three transits in front of it’s star are required to confirm an exoplanet and this may be longer than three Earth years for planets that orbit far from their star.  The Kepler mission is only 3.5 years, which may not be enough time to detect 3 transits of a planet that exists farther beyond the habitable zone.  Let’s hope that they are able to extend their mission for just long enough to confirm any stragglers.    The current list showing the sizes of planets detected by the Kepler telescope: 

*  207 Earth sized
*  680  Super Earth sized
*  1,181  Neptune sized
*  204  Jupiter sized
*  55  Super Jupiter sized

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