Newspaper article International Herald Tribune

Planet Circling Nearby Star Sets Scientists Abuzz

Newspaper article International Herald Tribune

Planet Circling Nearby Star Sets Scientists Abuzz

Article excerpt

Bringing the search for another Earth as close as it will ever get, astronomers say they have found a planet the same mass as Earth's in Alpha Centauri, a triple-star system only 4.4 light- years away.


Bringing the search for another Earth about as close as it will ever get, a team of European astronomers said that it had found a planet the same mass as Earth's in Alpha Centauri, a triple star system that is the Sun's closest neighbor, 4.4 light-years away.

The planet is the lightest one ever found orbiting another star and -- in the words of its discoverer, Xavier Dumusque, a graduate student at the Geneva Observatory -- "it will surely be the closest one ever."

It is presumably a rocky ball like our own, but it is not habitable. It circles Alpha Centauri B, a reddish orb about half as luminous as the Sun, every three days at a distance of about 4 million miles, or 6.4 million kilometers, resulting in hellish surface temperatures of 650 degrees Celsius (1,200 degrees Fahrenheit).

So this is not "Earth 2.0." Yet.

Astronomers said the discovery raised the possibility that there were habitable Earthlike planets right next door, and that methods and instruments were now precise enough to detect them.

"Very small planets are not rare," said Mr. Dumusque, who is the lead author of a paper, which was published Wednesday in Nature. "When you find one small planet, you find others." He and his colleagues discussed the results Tuesday in a news conference in Garching, Germany, hosted by the European Southern Observatory.

Astronomers were electrified by the news of the planet but also cautioned that it needed confirmation by other astronomers, not an easy task.

Debra Fischer, a Yale astronomer who has been searching for planets in that same system for years, said, "The discovery that our nearest neighbor has rocky planets is the story of the decade. I'd bet $100 that there are other planets that are there as well."

The discovery also underscored the allure of Alpha Centauri as a target of space and scientific exploration.

"This is close enough you can almost spit there," said Geoffrey Marcy, an exoplanet astronomer at the University of California, Berkeley.

Sara Seager, an astronomer at the Massachusetts Institute of Technology, said in an e-mail, "I feel like we should drop everything and send a probe there to study the new planet and others that are likely in the system."

There are three stars in that system. Alpha Centauri A, which is slightly larger and brighter than the Sun, and Alpha Centauri B, slightly smaller, are close companions, circling each other and passing as close as nine billion miles every 80 years. They in turn are being circled at a much greater distance, some one trillion miles, by a dwarf star known as Proxima Centauri, because it is slightly closer to the Earth than the other two. …

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