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Three new possibly habitable ‘super-Earth’ planets discovered

Artist conceptions of the habitable zone planets found so far by Kepler, compared to Earth on the far right. From left to right: Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f and Earth. Credit: NASA Ames / JPL-Caltech

Artist conceptions of the habitable zone planets found so far by Kepler, compared to Earth on the far right. From left to right: Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f and Earth.
Credit: NASA Ames / JPL-Caltech

There is some more exciting news from the Kepler space telescope mission – as announced in a NASA press briefing this morning, three more planets have been detected orbiting in their stars’ habitable zones. Larger planets have been found already in this zone around various stars, but what makes this newest discovery so compelling is that these new planets are the smallest found so far in this zone, so-called “super-Earths.” Two of them may even be covered by oceans!

The planets orbit two different stars, Kepler-62 and Kepler-69, and are known as Kepler-62e, Kepler-62f and Kepler-69c. They are actually three of seven total new planets found orbiting these stars, but the other four planets are not inside the habitable zones of the stars. Kepler-62 has five known planets and Kepler-69 has two. Kepler-62 is a K2 dwarf star, about two-thirds the size and one-fifth the brightness of our sun. Kepler-69 is a G-type star similar to our sun but about 93% the size and 80% as bright. Both stars are older than our sun. The Kepler-62 system is about 1,200 light-years from Earth while the Kepler-69 system is approximately 2,700 light-years away.

Kepler-62e is approximately 60% larger than Earth and Kepler-62f is only about 40% larger. Kepler-62f is most likely a rocky planet like Earth, and so is classified as a “super-Earth” – rocky planets which are a bit larger than Earth but smaller than ice giants like Neptune or Uranus. As explained in the press briefing, studies done so far suggest it may have oceans on its surface, just like Earth. Kepler-62e may also be rocky, and it may be a true waterworld, where all of its surface is covered by water – an endless ocean. Two ocean worlds in one solar system?

As stated by paper co-author Dimitar Sasselov of Harvard, “Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions. Kepler-62f would be cooler, but still potentially life-friendly.”

The third planet, Kepler-69c is about 70% larger than Earth, but its likely composition isn’t known yet. It’s orbital period around its star though, 242 days, is similar to Venus in our solar system.

The discoveries are another big step closer to finding habitable, Earth-sized planets orbiting other stars. They are the closest in size to Earth found so far which orbit in the habitable zone, where temperatures can allow liquid water to exist on their surfaces. Other planets smaller than Earth are also now starting to be found around other stars, but those ones (so far) are not in the habitable zone.

According to John Grunsfeld, associate administrator of the Science Mission Directorate at NASA Headquarters in Washington, “The Kepler spacecraft has certainly turned out to be a rock star of science. The discovery of these rocky planets in the habitable zone brings us a bit closer to finding a place like home. It is only a matter of time before we know if the galaxy is home to a multitude of planets like Earth, or if we are a rarity.”

This article was first published on Examiner.com.

4 Comments

  1. Because the attractive force we call gravity is so essential to us.

    What are the ‘G’ forces of these newly found planets ?

  2. Torbjörn Larsson, OM

    April 24, 2013 at 12:08 pm

    The back-of-the-envelope goes:

    Assume the same density. The mass goes as r^3. The gravity from an idealized point mass goes as r^-2. Then gravity goes as r^3/r^2 ~r.

    Such a gravity estimate for these planets, assuming the same composition (wrong here) and disregarding compressibility (also terribly wrong if water worlds), is 40 – 70 % more.

    It is interesting to note that cellular life doesn’t mind much for terrestrial range gravities. You can still have animals moving about in several g’s with the same type of muscles we have. With tension storage-release mechanisms like some insects and frogs, you can generate forces to move, with pauses and/or using parallel mechanisms, under 10’s, 100’s, if not 1000’s of g. (I’ll need to check that. But some accelerations created by their muscles are on that order.)

    Likewise we can withstand 1000s of g (but not rapid shaking, like explosions) if liquid immersed, which is why a fetus can take a lot of accidental abuse.

    And cells can withstand the pressure equivalent of 1000s of g in the deep ocean & crust.

    It would be interesting to know, if Kepler-62e&f are water worlds, presumably with 100s of km of global oceans, how far down the cellular potential biosphere (habitable zone) goes disregarding pressure ices that will eventually “surface” (appear at depth). I don’t think anyone has touched that question yet.

  3. Torbjörn Larsson, OM

    April 24, 2013 at 12:10 pm

    Oops. I meant that surface gravity goes as ~ r, naturally.

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