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posted by charon on Thursday May 18, @03:34AM   Printer-friendly
from the just-like-earth dept.

[N]ew models increasingly suggest that the closest Earth-like planet to our solar system could be habitable. Researchers first started playing a bit of "fantasy exoplanet" with the rocky world—dubbed Proxima b—last year after scientists discovered it orbiting our nearest neighbor star, Proxima Centauri. With knowledge only of the luminosity of the star (1/600 that of the sun), the mass of the planet (1.3 times that of Earth), and the length of its orbit (11.2 days), the team was able to predict that, with a variety of possible atmospheres, it would be possible for Proxima b to harbor liquid water on its surface.

Now, another team has upped the level of detail by taking a climate model designed for Earth—the Unified Model developed by the United Kingdom's Met Office—and pasted it onto Proxima b.

[...] As the team reports today in Astronomy & Astrophysics, it found an even wider range of circumstances in which Proxima b could have liquid water than the earlier study. The fact that the two very different models agree so closely is "somewhat remarkable," the team writes.

Source: Daniel Clery at sciencemag.org


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  • (Score: 2) by Bot on Thursday May 18, @06:08AM (1 child)

    by Bot (3902) Subscriber Badge on Thursday May 18, @06:08AM (#511555)

    If the study were good, the researcher would have thrown it out the window and done something else.

    Planet is habitable, meatbags settle in, make it unhabitable, bots settle in.

    Unless the study was by an AI, but then it would have been like a one liner what I just wrote.

    • (Score: 0) by Anonymous Coward on Thursday May 18, @06:32AM

      by Anonymous Coward on Thursday May 18, @06:32AM (#511560)

      Time for the B Ship to leave? After you, Mr Hawking...

  • (Score: 3, Interesting) by Anonymous Coward on Thursday May 18, @10:19AM (2 children)

    by Anonymous Coward on Thursday May 18, @10:19AM (#511621)

    I get this for the pressure-temperature profile of an earth like planet with the same Insolation as proxima B: http://i.imgur.com/FrpIdXr.png [imgur.com]

    Compare to figure 5 of the paper (https://arxiv.org/abs/1702.08463) and you'll see theirs is too hot by 10- 20 K.

    Here is my model in R:

    ## Stefan Boltzmann Law for two planets with different insolation
    # T_s1 = (S_1*(1-a)/(eps*sigma)^0.25
    # T_s2 = (S_2*(1-a)/(eps*sigma)^0.25

    ## Solve for surface temperature of planet 2 as a function of T_s1
    # T_s2 = T_1s*(S_2/S_1)^0.25
    # where:
    # S_2/S_1 = 0.646
    # T_s1    = 288

    # This yields
    T_s1 = 288
    T_s2 = 258.1967

    ## 1976 US standard Atmosphere constants
    p0 = 1013.25
    R  = 0.00831432
    g0 = 9.80665
    m0 = 0.0289644
    Le = -6.5

    # Aggregate Constant
    Ce = (g0*m0)/(R*Le)

    ## Calulate temperature for pressures from 1000 to 200 mbar, which
    #  corresponds to Earth troposphere pressures
    p   = seq(1000, 200, length = 1000)
    t_1 = T_s1/(p/p0)^(1/Ce)
    t_2 = T_s2/(p/p0)^(1/Ce)

    ## Initialize plot and plot Earth Pressure-Temp profile
    plot(t_1, p, type = "l", lwd = 2,
        xlab = "Temperature (K)",  ylab = "Pressure (mBar)",
        xlim = range(c(t_1, t_2)), ylim = rev(range(p)),
        log  = "y",
        panel.first = grid())

    ## Plot Proxima B profile
    lines(t_2, p, col = "Blue", lwd = 2)

    ## Add legend
    legend("topright", legend = c("Earth", "Proxima B"),
        col = c("Black", "Blue"),
        lwd = 3)

    • (Score: 1, Interesting) by Anonymous Coward on Thursday May 18, @10:36AM (1 child)

      by Anonymous Coward on Thursday May 18, @10:36AM (#511626)

      Actually I'm seeing their dayside for the tidally locked model (fig 5 still) matches Earth's mean profile almost exactly. This is kind of a strange coincidence.

      • (Score: 3, Interesting) by Anonymous Coward on Thursday May 18, @10:55AM

        by Anonymous Coward on Thursday May 18, @10:55AM (#511629)

        This is all same AC still. Now that I looked at the earlier paper[1] I see that one must be wrong too. If you check Fig 7 you see their model allows a troposphere above 0.1 bar. This is not seen for any planets/moons in the solar system, so is likely non-physical:[2]

        A minimum atmospheric temperature, or tropopause, occurs at a pressure of around 0.1 bar in the atmospheres of Earth, Titan, Jupiter, Saturn, Uranus and Neptune, despite great differences in atmospheric composition, gravity, internal heat and sunlight. In all these bodies, the tropopause separates a stratosphere with a temperature profile that is controlled by the absorption of shortwave solar radiation, from a region below characterised by convection, weather, and clouds.

        [1] https://www.aanda.org/articles/aa/abs/2016/12/aa29577-16/aa29577-16.html [aanda.org]
        [2] https://arxiv.org/abs/1312.6859 [arxiv.org]

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