Hundreds of Earth-sized planet candidates discovered

By Zaina Adamu, CNN

Could there be extraterrestrial life in our own Milky Way galaxy?

NASA’s Kepler mission, using an orbiting telescope equipped with a 95-megapixel camera and 42 charge-coupled devices, discovered that worlds, one-half to twice the size of Earth, exist in our galaxy.

Kepler is the first mission with the potential to identify Earth-sized planets that exist near the habitable zones of their stars, a landmark in astronomy because the finding could lead scientists to discover that, indeed, life exists in other places besides Earth.

The way Kepler detects planets is similar to how we detect Venus and Mercury from Earth. Every so often, there are events where Venus and Mercury pass the sun, briefly blocking a bit of the sunlight coming to Earth. From our perspective, each of these events, called a transit, is seen as a slow-moving black speck traveling across the sun.

The Kepler telescope searches for changes in the brightness of stars, which could provide evidence that planets are orbiting them.

Once a planet is found, its size can be measured using Kepler’s Third Law of planetary motion, a calculation based on the amount of light lost from a star and the star’s size. Additionally, the star’s temperature can help determine if the planet might be habitable.

Since its launch in March 2009, the Kepler telescope has found more than 2,300 planet candidates.

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