Earth has a cousin

On Friday July 24, NASA announced the discovery of Kepler 452b, a planet with characteristics similar to earth. Kepler 452b currently takes 385 days (slightly longer than our year) to orbit a sun-like star that is 1.5 billion years older than the sun and 20 percent brighter. There’s a possibility this planet could sustain some form of life. In order to determine whether Kepler 452b is actually potentially inhabitable, scientists would have to measure Kepler 452b’s mass directly, which at this point is impossible because the planet is 1,400 light years away.¬†Kepler 452b is one of 4,096 possible planets already discovered by the Kepler spacecraft since its launch in 2009¬†(see my prior musings about the Kepler spacecraft here).

What’s really fascinating is how planets are discovered. In order to find new planets, astronomers must rely on observing small irregularities in the parent star. For example, a star with a planet will have very slight variations in ‘wobble’ as a result of the gravitational pull of the planet.

Another way to determine the presence of a planet even when the planet cannot be seen directly is by observing minuscule changes in brightness of the parent star. As a planet passes in front of the host star, the star will appear slightly darker. Even though we cannot see the planet itself, by observing these slight variations in brightness or speed we can deduce that something (such as a planet) is causing the change.

The NY times states that:

“Astronomers say they now know from Kepler that about 10 percent of the 200 billion stars in the Milky Way have potentially habitable Earth-size planets.”

Stated another way, in our galaxy alone, it’s likely that there are 20 billion potentially habitable planets.

Amazing stuff.

Sources: Methods of detecting exoplanets (Wikipedia); NASA data reveals an earth-like planet, Kepler 452b (New York Times)


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