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Are There Planets Around Alpha Centauri?

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


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

Comments on this entry are closed.

  • Tobias Holbrok October 31, 2008, 1:41 PM

    Planets aren’t cpnsidered likely so no-ones bothered looking?

    A lot stranger things have happened….

  • psychonaut November 27, 2008, 9:53 PM

    The reason they can’t detect planets around our nearest neighbor is that they can only detect gas giants around stars within a 300 ly or so radius from Earth. They cannot see the planets, they can only see the gravitational effect of a planet as it pulls on a star and causes it to “wobble”. Since Alpha Centauri A & B are so close it is probably the case that gas giants did not have room and/or matter enough to form. After all, if Jupiter had gathered more matter early on, we might be living in a binary system.

  • psychonaut November 27, 2008, 9:58 PM

    Small, rocky worlds like the ones they are talking about do not have enough mass to affect the star in any observable way even if they are orbiting our nearest neighbor.

  • Anthony B Austin March 2, 2009, 1:55 PM

    Re Centaurian planets. In 1989 I authored a book
    with Brian Crowley (1938-2008) called “Return to
    Mars”. In this work we showed
    that the Icelandic Eddas (stories) said there
    were planets orbiting both alpha Centaurus A and
    B, stating that the one inhabitable world of B is
    called Fjalar. The book was republished by Black
    Rabbit Press in 2003. In the time elapsed, 14
    years, we thought that astronomy would confirm
    or deny our findings. Nobody did.
    We assume that the truth is scientifically
    unpalatable and an inhabitable world 4.3 ly away
    is too terrifying to contemplate.
    Anthony B Austin