Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone(www.science.org)
38 pointsby anyonecancode2 hours ago2 comments
  • WillAdamsan hour ago
    Is it wrong that I was hoping for something along the lines of:

    https://www.scientificamerican.com/article/how-would-we-know...

    except where they are noting how helium is being allowed to escape and not being captured as was previously done by the now shut down U.S. National Helium Reserve.

  • ck2an hour ago
    wow 50 light years is indeed "nearby" in relative terms

    nearly 6x the size of earth though, good luck trying to launch a probe off that surface

    NASA has a neat "exoplanet catalog" which is about to leap in size next few years with new telescopes and techniques

    * https://science.nasa.gov/exoplanet-catalog/lhs-1140-b/

    • pixl97an hour ago
      6x time size (diameter?) or 6 times the mass. Evidently the Earth used to be much larger in size but not mass because of large amounts of trapped hydrogen/helium. It's since leaked from the crust and been blown off into space.
      • ck236 minutes ago
        the catalog says 6.38x mass in one place and 5.6x mass in another

        they must be able to calculate mass from orbital physics?

        so you'd need a rocket 6x the size of SaturnV or whatever they are using for Artemis to escape it and most of that rocket is to lift the weight of the fuel for said rocket so it might be physically impossible to build such a creature at current level of tech

        (might be yet another angle to "why no ETs" unless they are WAY more advanced)

        • inigyou21 minutes ago
          √(G × mass÷radius) [escape velocity] = v_e × ln(m_0 ÷ m_f) [Tsiolkovsky]

          Impossible to tell how much extra mass you need but it's exponential. Adding a unit of v_e [effective exhaust velocity] to escape velocity means you need 2.717 times as much fuel in an ideal rocket.

          Earth escape velocity is 11000m/s ignoring atmosphere (which is not ignorable). If the new planet is 6x mass and 2x radius then √3 times escape velocity (about 1.73) would be about 8000m/s extra velocity which is about 3 times a random v_e which means you need about a 25 times bigger rocket. Ignoring the denser atmosphere which makes it even worse.

        • 26 minutes ago
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