Earth-sized planets: Two super-Earths found orbiting the same star.

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Scanning the heavens, you might very well miss the star Kepler-62. It’s a rather typical star, slightly smaller, cooler, and more orange than the Sun, much like tens of billions of other stars in our galaxy. But it holds a surprise: It’s orbited by at least five planets… and two of them are Earth-sized and orbit the star in its habitable zone!


The two planets, called Kepler-62e and Kepler-62f, are both bigger than Earth, but not by much; they are 1.6 and 1.4 times the Earth’s diameter, respectively. Kepler-62e orbits the star every 122 days, while Kepler-62f, farther out, takes about 267 days.

Given the temperature and size of the parent star, this means that both planets are inside the zone around the star where water on the surface could be a liquid. Now, to be clear, this depends on a lot of factors we don’t know yet: the masses of the planets, their compositions, whether they have atmospheres or not, and what those putative atmospheres are made of. For example, Kepler-62e could have a thick CO2-laden blanket of air, making its surface temperature completely uninhabitable, like Venus.

Or it might not. We just don’t know yet, and won’t for quite some time—both planets are too small to get a measurement of their masses. It’s worth noting, though, that we do have size and mass determinations for a few planets like this around other stars, and they look rocky, like Earth. That makes it likelier these two planets are as well.

Also, the best computer models we have, based on what we know about how planets form and change over time, indicate that these planets could very well have water on them (it is, after all, incredibly common both in our solar system and in the Universe at large). We've already seen at least one planet with indications of the presence of water.

Written By: Phil Plait
continue to source article at slate.com

8 COMMENTS

  1. Now, to be clear, this depends on a lot of factors we don’t know yet: the masses of the planets, their compositions, whether they have atmospheres or not, and what those putative atmospheres are made of.

    These are key questions. To be Earth-like, they need to be rocky (rather than gaseous) and have water and an atmosphere, – without being totally covered in deep water, or having a huge or tiny atmospheric pressure.
    They would also need a limited temperature range and an orbit and axis which maintained a limited temperature range.

    We also have to be careful about the term “rocky planet” (as distinct from gaseous). Water is a rock in the outer Solar System (even over much of Mars)!

    • In reply to #1 by Alan4discussion:

      • without being totally covered in deep water

      I don’t follow. Whales would be happy with a oceanic planet. We are constantly finding extremeophile forms of life on earth. Presumably life itself can go well beyond those limits, just that earth does not push it to (e.g. low air pressure, presence of what we consider toxins)

      • In reply to #3 by Roedy:

        In reply to #1 by Alan4discussion:

        without being totally covered in deep water

        I don’t follow. Whales would be happy with a oceanic planet. We are constantly finding extremeophile forms of life on earth.

        I was thinking in terms of human visits, rather than native life-forms. (Although whales – unlike fish, – required both land and sea for their evolution.)

        Presumably life itself can go well beyond those limits, just that earth does not push it to (e.g. low air pressure, presence of what we consider toxins)

        Past Earth life and present extremophiles have certainly indicated a range, but be cannot make assumptions for or against an extended range, particularly if there are more limited time-scales in which to adapt.

  2. It seems unlikely that life, certainly as we know it, would have evolved here without the protection provided by our Iron core, which generates Earth’s magnetic shield against solar radiation. Should we therefore assume that a similar shield would be needed on any other planet in order to harbour our kind of life.

    Just to be clear, by “our kind of life” I mean at a minimum multi-celled organisms existing in the top layers of bodies of water, right up to things walking around on dry land. I do not mean humans or close analogues.

    If this is a necessity can we (now or in the near future, maybe 50 or so years,) detect such an extra-solar magnetic field?

    • In reply to #6 by SomersetJohn:

      It seems unlikely that life, certainly as we know it, would have evolved here without the protection provided by our Iron core, which generates Earth’s magnetic shield against solar radiation. Should we therefore assume that a similar shield would be needed on any other planet in order to harbour our kind of life.Just to be clear, by “our kind of life” I mean at a minimum multi-celled organisms existing in the top layers of bodies of water, right up to things walking around on dry land. I do not mean humans or close analogues.If this is a necessity can we (now or in the near future, maybe 50 or so years,) detect such an extra-solar magnetic field?

      Mass and size can tell a lot but not if the core of a planet is still liquid or solid, or like Earth both. Size might be just as hard to measure as the magnetic field of a small planet. However, I wouldn’t be surprised when scientists will find a cunning way to detect and measure either. Who would have thought that the doppler shift of star light could tell that a planet is orbiting that star?

      And life as we know it, well, we are a chemical reaction, fueled by the sun. A terribly complicated chemical reaction but none the less that’s what we are. (Why do I feel like a nihilist right now?) Any continued, self-replicating chemical reaction would be interesting, but I bet, ones we have found life elsewhere in the universe it would be different from anything we have fantasized about. I can’t wait.

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