Earth-Like Planet Found in Nearest Star System

Astronomers discovered a planet right next door, cosmically speaking, but it's still out of reach.

This artist’s impression made available by the European Southern Observatory on Tuesday, Oct. 16, 2012 shows a planet, right, orbiting the star Alpha Centauri B, center, a member of the triple star system that is the closest to Earth. Alpha Centauri A is at left. The Earth's Sun is visible at upper right.
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Scientists have discovered an Earth-like planet orbiting a Sun-like star in the solar system nearest to Earth. But don't expect to buy a ticket there anytime soon since the planet is about 25 trillion miles away—meaning it would take 40,000 years for a probe launched using current technology to reach it.

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The planet, dubbed Alpha Centauri Bb, orbits a star in the Alpha Centauri system, a clump of three stars that are closer to us than any others in the night sky. It's called Alpha Centauri Bb because the planet orbits the clump's second-closest star, Alpha Centauri B.

Unfortunately, not only is Alpha Centauri Bb well beyond current spacefaring technology, it also wouldn't be much of a pleasant vacation spot—especially if you sun burn easily. The Earth-sized planet orbits its sun much closer than Mercury does to ours. As a result, Alpha Centauri Bb's "year" lasts only 3.2 days and its molten-lava surface temperature is about 2,240 degrees, according to Space.com.

Despite its unreachable distance and unbearable heat, the planet's discovery is an exciting moment in the search for Earth-like planets that could harbour life, says Xavier Dumusque, a scientist at Geneva Observatory and lead author of the paper that published the discovery.

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"Our observations extended over more than four years... and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days," said Dumusque. "It's an extraordinary discovery and it has pushed our technique to the limit!"

Using a special instrument that detects signal variations from distant stars attached to the European Southern Observatory's telescope in La Silla, Chile. Dumusque and his colleague noticed a slight wobble in Alpha Centauri B's gravity, which they deduced to be a planet. Even this neighbor planet is too far away to see. For perspective, a ray of light takes about seven minutes to reach Earth from the Sun. It would take only about 16 hours to reach the furthest man-made object from Earth, the Voyager 1 probe, which launched in 1977 and is near the edge of the solar system. It would take about 4.3 years to reach Alpha Centauri Bb.

Still, Alpha Centauri Bb is the first of more than 800 discovered exoplanets, or planets outside our solar system, that are around the same size as Earth.

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"This result represents a major step towards the detection of a twin Earth in the immediate vicinity of the Sun. We live in exciting times!" Dumusque said.

Seth Cline is a reporter for U.S. News and World Report. You can follow him on Twitter or reach him at scline@usnews.com.