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Earth-like planets pile up

phot-39a-09-fullres.jpgA ground-based survey has turned up still more Earth-like exoplanets, including one on the inner edge of the so-called “habitable zone”, where conditions might be right for life. Maybe.

The High Accuracy Radial velocity Planet Searcher (HARPS) is a high-quality spectrograph attached to a 3.6 meter telescope in La Silla on the edge of Chile’s high-altitude Atacama desert. The instrument is designed to look for tiny wobbles in a star’s light created by planets as they orbit it.

The system is among the most sensitive available and has already spotted over 100 new worlds in the eight years it’s been running. Most of those have been objects with roughly the mass of Neptune, but HARPS also revealed Gliese 581, which is home to a planet just under twice the mass of Earth and inside the habitable zone.

The real prize in the planet-hunting business is discovering ‘Earth 2.0’ — an Earth-sized planet orbiting a star at a distance similar to our own. The best shot at such a discovery may go to Kepler, a NASA mission which is currently surveying around 150,000 stars for tiny planetary eclipses. The Kepler telescope is in the coldest reaches of space, which gives it a serious edge over those stuck on the ground.

But the HARPS team thinks it might have a chance of beating Kepler to the punch. Based on the frequency with which the team spotted planets previously, they decided to look at ten stars that were near enough to allow them to see smaller planets closer to their stars. Three out of the ten do indeed appear to have low mass planets orbiting them. One system has two Neptune-sized objects (yawn); one has three super-Earths outside the habitable range (sigh). But one, known by the catchy name HD 85512, has a 3.6 Earth-mass planet “just inside” the habitable zone.

Just because its habitable doesn’t mean that you’d want to habit it though. The planet is warmer than the Earth, and the authors don’t rule out a cloud-covered hell-hole (think Venus). For true Earthiness, we may have to await further results from Kepler.

Image: The Gliese 667 system, ESO/L. Calçada


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    James T. Dwyer said:

    Is there any capability to determine whether any of these ‘Earth-like’ planets might include a single, relatively large, stabilizing moon like Earth’s?

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    dr hagus said:

    At 36 light years from Earth, it is not clear how HD 85512 will ever be amenable to exploration other than by these kinds of indirect measurements, which by themselves will never be able to prove or disprove the presence of extraterrestrial life. However, based on the frequency of exoplanet discovery even within our neighboring stars, it is simply inevitable now that there is abundant life throughout the universe.

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