Distant Cousin



Source: NASA/Ames/JPL-Caltech (

We often look at the night sky and wonder if there’s anybody out there, are we alone in the universe, how far is the planet, or planets that could host life similar to life on Earth, how would they look, the questions just keep piling up, which goes to show that the idea of life on other planets never stops fascinating us. With the discovery of exoplanets that could possibly host life, that idea might just become reality. Exoplanets, or extrasolar planets, are planets outside or Solar System. Around a thousand such planets has been discovered, or to be more exact, 981 planets in 750 planetary systems including 163 multiple planetary systems as of 21 September 2013. The Kepler mission space telescope has detected thousands more candidate planets, including 262 that may be habitable planets. One of those planets that has created quite a buzz since its discovery is a planet called Kepler 22-b. What do we know about it?

For starters, Kepler 22-b is an exoplanet that is roughly the same size as our Earth, with an orbit inside the inhabitable zone, which could be a step in the direction regarding the discovery of life on other planets. Discovered by the Kepler satellite, Kepler 22-b orbits around a star that is similar to our Sun, only a bit smaller, fainter and older. It is located in galaxy that is about 600 light years away from Earth. As far its physical properties are concerned, there’s very little scientists can tell us for now. What they can do is make an educated guess based on a number of factors. For example, if we were to make a rough categorization of the planets, we would divide them into two groups: those made of rock, and those made gas.

Gaseous planets, like Jupiter and Saturn, are usually larger and lots of planets with similar characteristics have been found because they are easier to locate then the ones that have a solid surface. This is due to the fact that the rocky planets are smaller, so they block less light when they transit, making them harder to locate. If we take into account the size of Kepler 22-b, which about 2.4 times the size of Earth, we can determine its volume. It would be great if we could also determine its mass, then we could work out the density. If the density is smaller that 1000 kilograms per cubic meter, it possibly made out of water, or, if its density is over 5000 kilograms per cubic, it is probably made out of rock.

The Kepler team has also worked out that the planet is likely to have temperature of about 22 degrees Celsius, which is perfect for liquid water. However, this estimate is based on the assumption that Kepler 22-b has the same kind of atmosphere as our Earth. Also, one needs to take into account the possibility of tidal locking, which decreases Kepler 22-b’s chances of being inhabitable. Tidal locking is when a body rotates “in step” with another body that it’s orbiting, so that it rotates once on its axis for every orbit, similar to relationship between our Moon and Earth.

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