Home > Uncategorized > First Earth-like exoplanets discovered, NASA says

First Earth-like exoplanets discovered, NASA says

Two planets outside of our solar system that are approximately the size of Earth have been discovered by researchers using the Kepler space telescope, NASA announced last week.

The exoplanets are too close to their star to allow liquid water to exist on their surfaces and are therefore unlikely to be habitable.

“This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them,” Francois Fressin, a researcher at the Harvard-Smithsonian Center for Astrophysics and the lead author of the study that documents Kepler’s new discovery, said.

The two exoplanets are the smallest found by the Kepler space telescope thus far.

They are about 950 light years from Earth and are part of a solar system called Kepler-20, which is located in the constellation Lyra.

Kepler 20e, the second planet in the system, is about 87 percent as big as Earth, with a diameter of 6,900 miles. It has a period of revolution of 6.1 days and the temperature on its surface is about 1,400 degrees Fahrenheit.

Kepler 20f, the fourth planet in the compact system, is slightly larger than Earth, with a radius three percent larger than Earth’s. Its diameter is 8,200 miles.

The average surface temperature on Kepler 20f is about 800 degrees Fahrenheit, which is slightly cooler than the surface temperatures on Mercury and Venus.

Kepler 20f’s year lasts 19.6 days.

Three other planets also populate the Kepler-20 system. All five of the planets orbit the star at a distance that is less than that of Mercury to our Sun.

The planet farthest from Kepler-20, Kepler 20d, completes a revolution of the star in less than 80 days.

The Kepler-20 system is unusual in another way as well. Its planets alternate in size from relatively large to relatively small.

In our solar system the smaller planets are closer to the Sun, with the outer planets significantly larger in size.

Scientists use a planet’s transit of a star, which is observed in the form of diminished brightness in the star’s light, to search for exoplanets.

If a transit of a distant star is detected, scientists proceed to calculate the exoplanet candidate’s orbital size from the time it takes for the transit to be repeated and the mass of the star it orbits.

Scientists then determine the size of the exoplanet by measuring the decline in the star’s brightness and the size of the star. They can then calculate the exoplanet’s average surface temperature from the orbital size and the temperature of the star.

If a transit is seen at least three times then scientists use Earth-based telescopes and the Spitzer Space Telescope to verify possible exoplanet candidates.

Kepler will observe more than 150,000 stars during its three and one-half year-long mission.

Boulder-based Ball Aerospace and Technologies Corp. supports mission operations for the Kepler space telescope along with the University of Colorado at Boulder’s Laboratory for Atmospheric and Space Physics.

The study documenting the discovery of Kepler 20e and Kepler 20f appears in the Dec. 20 edition of Nature.

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