Finding a Habitable Planet

Not Too Far Away

An artist's concept by Lynette Cook of the planet found around Gliese 581.

The news of a new planet only three times the size of Earth and orbiting in its star’s potentially habitable zone spurs on the great speculation that it’s only a matter of time before we find a planet with some sort of life on it.

The star is called Gliese 581, a red dwarf that lies only 20 light-years from Earth. The planet is called Gliese 581g. This discovery was the result of more than a decade of observations using the W. M. Keck Observatory in Hawai’i.

Finding a planet in a potentially habitable zone means that the planet lies in an orbit around the star that is just far enough away (but not too far away) that liquid water could exist on the planet’s surface.  That water hasn’t yet been found on the Gliese 581g, but the fact that it’s in the right place — the so-called “Goldilocks zone” is important.

Water is one of the prime ingredients for life, along with warmth and organic material.  If water is eventually found on the newly discovered planet, that would make it the most Earth-like exoplanet yet discovered and the first strong case for a potentially habitable one.  To astronomers, a “potentially habitable” planet is one that could sustain life, not necessarily one where humans would thrive.  Having habitable status depends  on more than just water and an atmosphere, but those two factors really raise the odds of the planet being hospitable to life.

So, how did astronomers find this planet?  The research is based on 11 years of observations of Gliese 581 using the HIRES spectrometer on the Keck I Telescope. That instrument lets astronomers make precise measurements of a star’s radial velocity (its motion along the line of sight from Earth). Changes in that radial velocity might indicate that something is tugging on the star, inducing slight changes in its motion in space.  The gravitational influence of an orbiting planet is one reason why we might see periodic changes in the radial velocity of a host star. Multiple planets induce complex wobbles in the star’s motion, and astronomers use sophisticated analyses to detect planets and determine their orbits and masses.

NO Intelligent Life.. or Any Life… Yet

As you might expect, some commentators and reporters in the media and Web-based React-O-Sphere are already breathlessly reporting the discovery of life on that planet.   It isn’t so.  Hasn’t been found. Yet.  The discovery is of a “potentially habitable planet” not an inhabited one. There’s a distinct difference when you stop to think about it.

But, that hasn’t stopped the React-O-Sphere from saying it.  It tells me that those commentators either didn’t read the press releases carefully or didn’t understand them.  This story is a great case for the value of reading comprehension on the part of the media and Web commentators.

For the straight scoop on what HAS been found, check out the link at the top, or go here or here.  That way you can get more of the story — straight from the sources who made the discovery.


  1. I reckon myself a teeming-worlder — someone who believes in the Saganesque vision of a galaxy teeming with planets, some generous fraction of which are habitable by “life as we know it.”

    So this discovery of Gliese 581G is very good news. Of course it doesn’t prove that Earthlike worlds are out there in profusion. But, more and more, it looks to me like that’s the way to bet.

    And thanks for putting this blog together. I’ll be spending some time on it.

  2. Pingback: Carnival of Space 172 « Lights in the Dark

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