Are There Planets Around Alpha Centauri?

by Fraser Cain on March 10, 2008

Artist illustration of planets around Alpha Centauri. Image credit: UC Santa Cruz
We’re holding out hope for the next generation of planet-finding observatories to locate Earth-sized planets orbiting other stars. But hold on, maybe we don’t need a super space observatory like ESA’s Darwin just yet. In fact, if our nearest neighbour Alpha Centauri has Earth-sized planets, we should be able to detect them with established techniques… right now, with the observatories we have today.

University of California researcher Javiera Guedes has developed a computer simulation that shows that Alpha Centauri B – the largest star in the nearby triple-star system – should have terrestrial planets orbiting within its habitable zone, where liquid water can exist.

They ran several simulations of the system’s first 200 million years. In each instance, despite different parameters, multiple terrestrial planets formed around the star. In every case, at least one planet turned up similar in size to the Earth, and in many cases this planet fell within the star’s habitable zone.

Guedes and co-author Gregory Laughlin think there are several reasons why Alpha Centauri B makes an excellent candidate for finding terrestrial planets. Perhaps the best reason is that Alpha Centauri is just so close, located a mere 4.3 light years away. But it’s also positioned well in the sky, giving it a long period of observability from the Southern Hemisphere.

Most of the 228 extrasolar planets discovered to date have been with the Doppler technique. This is where a planet pulls its parent star back and forth with its gravity. The star’s relative velocity in space changes the wavelength of light coming from it which astronomers can detect. Until now, only the largest planets, orbiting at extremely close distances from their parent stars have been discovered.

But with a nearby star like Alpha Centauri B, much smaller planets could be detected.

The researchers are proposing that astronomers dedicate a single 1.5-metre telescope to intensively monitor Alpha Centauri over a period of 5 years. In that time, any change in the star’s light should be detectable by this telescope.

“If they exist, we can observe them,” said Guedes.

Original Source: UCSC News Release

About 

Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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