How Earthlike are Kepler’s Latest Exoplanets?

I am sure everyone is aware of the latest release of exoplanet data from Kepler that has multiplied the number of known exoplanet candidates by a factor of about five. Kepler detects its exoplanets by looking for stellar transits so it is only going to see them in the rare cases where we are in alignment with the plane of the stars planetary system. Luckily it can look at a lot of stars in a patch of the sky all at the same time. In its first few months it has found well over a thousand by this method. Some of these may prove to be glitches and must be verified either by land-based observations of by repeat transits observed from Kepler.

So which is the most Earthlike  planets they have seen? To answer this you need to peruse the full set of data which can be found here. Even then the answer depends on what you consider to be the most important parameters to define an Earthlike planet. After due consideration I am going to go for Keplar-268 which has an estimated radius of 1.75 times the Earth, a year of 110 days and it sits at 0.41 astronomical units from its parent star. This should give it an estimated surface temperature of 295 degree Kelvin or 22 degrees Celcius. Admittedly it is a bit large so its gravity is going to be stronger than  we would probably enjoy.

The estimated temperature that NASA uses is based on the amount of received radiation. I’m not sure if there is any correction for greenhouse effects which depend on the density and content of its unknown atmosphere. In any case it is at least reasonable to assume that its rotation will not be locked to its star so it has a chance of being habitable with liquid water present. On the other had it’s high gravity may mean it retains too much atmosphere and suffers from permanent clouds making its surface very hot and high pressured.

This is just the first big release of data from Kepler and more can be expected, especially since many Earthlike planets will not have done a full revolution of their star in the time it has been l0oking. The results so far suggest that when all data is collected there should be some candidates for really Earthlike planets, at least in terms of size and ambient temperature. Once their location is known it will be the job of other telescopes to look at them in more detail. This will include the best Earth-based telescopes using adaptive optics and interferometry to focus in on the systems. A little later the James Webb Space Telescope should take over, if and when it successfully reaches its position to start observing in space.

8 Responses to How Earthlike are Kepler’s Latest Exoplanets?

  1. Ulla says:

    ExoPlanetNews is an monthly electronic Newsletter listing abstracts of newly accepted papers in the Exoplanet Field including:

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    * Planetary evolution and habitability
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  2. Luboš Motl says:

    This looks like a great planet. And 1.75 times our radius is not too bad – it means gravity of 2g or something like that, doesn’t it?

    If your promised temperature equal to my current room temperature is OK, that would be terrific. It would disprove the statements that there is no Planet B. 😉

  3. Lawrence B. Crowell says:

    If we assume an Earth density the gravity would be g = 2.3g_{earth}. I once read a science fiction story about a prison planet where the gravity was twice that of Earth. It kept the prisoners “down,” and short lived as their hearts gave out sooner.

    Of course these planets are “candidates,” and the proof is in the optical pudding from Keck and others. However, I suspect a good percentage of these will pan out. As for there being biologically active planets, that will require space based optical interferometers able to look much closer. Yet I suspect if we keep looking we may find one.

  4. For TGD inspired comments about the 6-planet system Kepler-11 see this.

  5. the quest of Earthlike planets is not so easy as it seems to be at first sight

    everybody thinks Earth is in the habitable zone of the Sun

    but it is not..

    Earth is not in the habitable zone of the Sun..

    .the planet in the habitable zone of the Sun is…Mars!!!

    the Moon keeps the same distance of the Earth with respect to the Sun and in the bright side the Moon temperature is 300 degrees Celsius

    Earth have a magnetic field…eg Van Allen Belt that deflects incoming particles and microwave radiations from the Sun that otherwise would raise the temperature of Earth to 300 degrees Celsius and cook our planet and vaporize the oceans creating a cloud blanket similar to the one of Venus

    Mars is in the habitable zone of the Sun…but do not have oceans

    • Lawrence B. Crowell says:

      I suppose I had not heard that Earth was not in the habitable zone. Of course this might depend on how that is defined. Without CO_2 in our atmosphere temperatures would be about 20-30C colder. Mars is also pretty cold, but of course its atmosphere is tenuous and thin. The geology and chemistry of a planet are very important in determining the temperature at its surface. It also appears that the range of possible configurations for a planet, both its orbital configuration in a stellar system and its physical characteristic is enormous.

      Cheers LC

  6. Bill K says:

    From a distance, what could be more alike than the four Galilean satellites of Jupiter. And yet, up close, what could possibly be more different. Despite being stuck pretty much in the same place, they’ve apparently undergone a radically different history. So, habitability is not just a matter of location. Luck must play a large part!

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