Headlines > News > Potentially habitable planet discovered

Potentially habitable planet discovered

Published by Klaus Schmidt on Thu Sep 30, 2010 7:31 am via: Eurekalert
Share
More share options
Tools
Tags

Astronomers have found a new, potentially habitable Earth-sized planet. It is one of two new planets discovered around the star Gliese 581, some 20 light years away.

Artist illustration of a super Earth around Gliese 581. Credit: ESO

Artist illustration of a super Earth around Gliese 581. Credit: ESO

The planet, Gliese 581g, is located in a “habitable zone”—a distance from the star where the planet receives just the right amount of stellar energy to maintain liquid water at or near the planet’s surface. The 11- year study, published in the Astrophysical Journal and posted online at arXiv.org, suggests that the fraction of stars in the Milky Way harboring potentially habitable planets could be greater than previously thought—as much as a few tens of percent.

The new study brings the total number of planets around Gliese 581 to six and, like our own solar system, they orbit their star in nearly circular orbits. The scientists, members of the Lick-Carnegie Exoplanet Survey, collected 11 years of radial velocity data on the star. The radial velocity method looks at a star’s tiny movements in response to the gravitational tug from orbiting bodies. The team tracked the motion of the planets to a precision of about 1.6 meters per second.

The amplitude and phasing of the star’s subtle gravitational reactions allow researchers to determine a planet’s mass and orbital period. The planet’s radius is estimated by making assumptions about its composition, and its surface gravity is calculated from its mass and radius. Astronomers can also determine the planet’s equilibrium and surface temperatures, which help to determine the potential for habitability. Equilibrium temperature reflects the balance between the energy emitted from the planet and the thermal energy received from the star. The surface temperature is estimated by the planet’s distance from the star and a range of guesses about the composition of its atmosphere. To be habitable, the temperatures must not be too hot, which would vaporize water, nor too cold.

The orbits of planets in the Gliese 581 system are compared to those of our own solar system. The Gliese 581 star has about 30% the mass of our sun, and the outermost planet is closer to its star than we are to the sun. The fourth planet, G, is a planet that could sustain life. Credit: National Science Foundation/Zina Deretsky

The orbits of planets in the Gliese 581 system are compared to those of our own solar system. The Gliese 581 star has about 30% the mass of our sun, and the outermost planet is closer to its star than we are to the sun. The fourth planet, G, is a planet that could sustain life. Credit: National Science Foundation/Zina Deretsky

“Our calculations indicate that the planet is between 3.1 and 4.3 Earth masses, has a circular 36.6-day orbit, and a radius estimated between 1.2 and 1.5 Earth radii,” remarked co-author Paul Butler of Carnegie’s Department of Terrestrial Magnetism.

Its semi-major axis—half the length through the long direction of its elliptical orbital path—is 0.146 astronomical units (one AU is the distance between the Earth and the Sun), and its surface gravity is similar to Earth’s at 1.1 to 1.7 g.

Habitability depends on many factors, not just the temperature. The gravity has to be strong enough to hold an atmosphere, for instance, and the temperature must be lower than about 26° F somewhere on the planet. The researchers estimate that the surface temperature of the newly discovered planet is between -24° F and 10° F. The surface would be blazing hot on the side facing the star and freezing cold on the dark side. The planet might be tidally locked to the star—with one side always facing the star, and the other side always dark and cold. This serves to stabilize the planet’s surface climates, according to Steven Vogt, co-author and professor of astronomy and astrophysics at UC Santa Cruz. The most habitable zone on the planet’s surface would be along the line between shadow and light, with surface temperatures decreasing toward the dark side and increasing toward the light side.

Temperatures on Earth vary tremendously, and life can thrive in very extreme environments, ranging from Antarctica, where the temperature can get to -94 ° F, to extremely hot hydrothermal vents, which roil at 235 ° F.

The fact that the researchers were able to detect this planet so quickly and so nearby (in astronomical terms) suggests that habitable planets could be quite common.

9 Comments
Really, this news got me ecstatic yesterday! =D
Indeed, this is big news. I spent the day pondering what life would be like on a tidally locked rocky earthylike planet.

Do the seas boil on the sunward side, then freeze into huge glaciers on the darkward side? Or maybe the seasons are so constant as to have essentially fixed seasons all over the planet.

If the planet had significant atmosphere (as much or more than earth) would that mean that air currents could stabilize the temperature? Constant hurricane-like winds to transport all the heat.

And, if the sun is always on the horizon, then all the plants (were one to hypothetically imagine something plantlike could have arisen there) would face sideways. Seems to me there'd be quite a different set of circumstances for any life there. It's interesting to speculate.

I want to know, what do we need (technologically) to learn more about worlds like this? 30m telescopes? orbital interferometer arrays?

I want a picture of this planet good enough to make out continents. That would be awesome. Probably need an aperture with the surface area of a small city to get something like that I suppose.
I like your question about air currents carrying the heat, and the plants probably on one edge of that habitable vertical band of land. :)
"I want to know, what do we need (technologically) to learn more about worlds like this?"

Build starships and go there?

Telescopes from Earth are never going to resolve the the planet into anything like an "image". The best you will get is isolate the light from it to be able to Anallise its spectra.
That's not necessarily correct. Formalhaut lies ~5 LY further away than Gliese 581 and we already have a picture, even if its only a spot of light, taken by hubble. So with the future upcoming 30 (TMT) and 42 (E-ELT) meter telescopes there will certainly be quite a few more direct images of exoplanets.
I left out part of a sentence: "we already have a picture [of one of its planets],..."
We need to develop a photonic engine which allows us to go faster than light. :)

But a probe with such an engine could give us images, that'd be awesome!
Yes you can take a picture of a planet, but its just going to be a point of light. I don't think we'll have the angular precision to actually build an image of the disk of something so small and far away.

And Formalhaut b is probably a super-Jovian and in the middle of a planetary nebula, so it made an easy target.
Leave a reply
You must be logged in to post a comment.
© 2014 The International Space Fellowship, developed by Gabitasoft Interactive. All Rights Reserved.  Privacy Policy | Terms of Use