6 ms·

Plus at 5.8 times (+-1.9) Earth's mass it's only low mass compared to most extrasolar planets. Still, there may be life that's happy with slow and heavy.

by hazeii 7y ago

arethuza 7y ago
That massive a planet might have a thick enough atmosphere to compensate for its distance from the star? e.g. Wasn't Mars 'warm' for quite a long time and only became really cold once it lost most of its atmosphere due to its small mass?
- PopeDotNinja 7y ago
  Titan has a darn thick atmosphere, and it's a moon of Saturn. I don't see any reason the planet from the article couldn't have an atmosphere.
  - saiya-jin 7y ago
    Isn't some of the atmosphere being replenished from its inner geology? Also IIRC Mars lost its atmosphere due to solar winds and lack of good protective magnetic field, unlike earth with its radioactivity-fed one. I would expect Titan has it neither, but is much farther from Sun so solar winds must be a tiny fraction of intensity out there.
    - ourlordcaffeine 7y ago
      >IIRC Mars lost its atmosphere due to solar winds and lack of good protective magnetic field Someone in the know correct me if I'm wrong, but I believe this is no longer the main theory, as solar wind ablation is too slow to make such a huge impact. I believe the popular explanation now is that geological reactions, i.e. gas reacting with rocks and being sequestered, played a larger part.
      - zipwitch 7y ago
        Solar wind as the culprit was still being tossed around in 2017. https://www.nasa.gov/press-release/nasas-maven-reveals-most-of-mars-atmosphere-was-lost-to-space https://www.nasa.gov/press-release/nasas-maven-reveals-most-... "The new result reveals that solar wind and radiation were responsible for most of the atmospheric loss on Mars, and the depletion was enough to transform the Martian climate."
        ourlordcaffeine 7y ago
        Ah, maybe I read that geological processes were ruled out rather than being the main driver
    - ryanmercer 7y ago
      Titan keeps its atmosphere, in part, because of Saturn's magnetosphere. It is inside it something like 95% of the time.
    - eloff 7y ago
      Radioactivity fed? Indirectly by producing heat and motion in the core?
- nkrisc 7y ago
  As I understand it didn't become cold because it lost its atmosphere, it lost its atmosphere because it became cold (core solidified weakening the magnetic field). It's core solidified much sooner than Earth's will because it has much less mass so it cooled quicker.
jbotz 7y ago
Keep in mind that surface gravity depends very much on density. The earth is pretty dense, having a core of mostly iron. Even a rocky planet can be a lot less dense if it's iron-poor, and so could have a reasonable surface gravity (by our standards) even if several times the earth's mass.
- bmgxyz 7y ago
  Indeed. I learned this the hard way when I made some claim to a political science roommate about the local acceleration due to gravity near one of the outer planets and was corrected and embarrassed. It's easy to forget that gravitation is the result of many tiny things all pulling on each other, not just a few big and small things. I looked through the paper and didn't see anything about the radius of the planet candidate. I suppose it's quite difficult to determine it from so far away. Is a value known? If so, that would obviously give a good idea about the local g.
  - Robotbeat 7y ago
    The radius is often not known. Radius is found most easily with transiting exoplanets, which are easy to detect but also only visible if you're lined up along the plane of the exoplanet's orbit. You can also possibly find it via imaging, but even then, since you can't directly resolve it better than a point light source, you're making assumptions about albedo that lead to a wide dispersion in possible radii. High resolution optical imaging would require a telescope roughly 1-2km in diameter. Pretty tough... and because of the glare of the star, would be nearly impossible to image with an interferometric (i.e. non-filled-aperture) telescope since the light gather power would be so low. However, astronomers are incredibly clever at pulling data out of tiny points of light, so there may be some way.
    - bmgxyz 7y ago
      Thanks for this, it's quite interesting. I have a friend who used to work in a lab doing super-resolution microscopy (i.e. beating the diffraction limit by various means) for use with bio/medical applications. Some of the techniques he told me about have to do with more or less taking lots of data from many images and assembling it all into something meaningful. I suppose what you're describing as "pulling data out of tiny points of light" is kind of the same thing. It's just that the scale is different.
matt123456789 7y ago
Most extrasolar planets that we have detected. It’s harder to detect the smaller ones, so we haven’t. Future space telescopes will have the equipment to help with this problem.
skykooler 7y ago
Note that this is the second planet found around Proxima Centauri. The first one is only 1.3 Earth masses and sits 0.05 AU away from the sun, which puts it in the potential habitable zone.
- exdsq 7y ago
  0.05 AU seems dangerously close to the sun?
  - ceejayoz 7y ago
    Not for a tiny, weak star like Proxima Centauri. https://en.wikipedia.org/wiki/Proxima_Centauri_b https://en.wikipedia.org/wiki/Proxima_Centauri_b > The host star, with about an eighth of the mass of the Sun, has a habitable zone between ∼0.0423–0.0816 AU.
    - exdsq 7y ago
      I didn’t know that! Thanks :)

Plus at 5.8 times (+-1.9) Earth's mass it's only low mass compared to most extrasolar planets. Still, there may be life that's happy with slow and heavy.

by hazeii 7y ago

Plus at 5.8 times (+-1.9) Earth's mass it's only low mass compared to most extrasolar planets. Still, there may be life that's happy with slow and heavy.

arethuza 7y ago

That massive a planet might have a thick enough atmosphere to compensate for its distance from the star? e.g. Wasn't Mars 'warm' for quite a long time and only became really cold once it lost most of its atmosphere due to its small mass?

PopeDotNinja 7y ago
Titan has a darn thick atmosphere, and it's a moon of Saturn. I don't see any reason the planet from the article couldn't have an atmosphere.
- saiya-jin 7y ago
  Isn't some of the atmosphere being replenished from its inner geology? Also IIRC Mars lost its atmosphere due to solar winds and lack of good protective magnetic field, unlike earth with its radioactivity-fed one. I would expect Titan has it neither, but is much farther from Sun so solar winds must be a tiny fraction of intensity out there.
  - ourlordcaffeine 7y ago
    >IIRC Mars lost its atmosphere due to solar winds and lack of good protective magnetic field Someone in the know correct me if I'm wrong, but I believe this is no longer the main theory, as solar wind ablation is too slow to make such a huge impact. I believe the popular explanation now is that geological reactions, i.e. gas reacting with rocks and being sequestered, played a larger part.
    - zipwitch 7y ago
      Solar wind as the culprit was still being tossed around in 2017. https://www.nasa.gov/press-release/nasas-maven-reveals-most-of-mars-atmosphere-was-lost-to-space https://www.nasa.gov/press-release/nasas-maven-reveals-most-... "The new result reveals that solar wind and radiation were responsible for most of the atmospheric loss on Mars, and the depletion was enough to transform the Martian climate."
      - ourlordcaffeine 7y ago
        Ah, maybe I read that geological processes were ruled out rather than being the main driver
  - ryanmercer 7y ago
    Titan keeps its atmosphere, in part, because of Saturn's magnetosphere. It is inside it something like 95% of the time.
  - eloff 7y ago
    Radioactivity fed? Indirectly by producing heat and motion in the core?
nkrisc 7y ago
As I understand it didn't become cold because it lost its atmosphere, it lost its atmosphere because it became cold (core solidified weakening the magnetic field). It's core solidified much sooner than Earth's will because it has much less mass so it cooled quicker.

jbotz 7y ago

Keep in mind that surface gravity depends very much on density. The earth is pretty dense, having a core of mostly iron. Even a rocky planet can be a lot less dense if it's iron-poor, and so could have a reasonable surface gravity (by our standards) even if several times the earth's mass.

bmgxyz 7y ago
Indeed. I learned this the hard way when I made some claim to a political science roommate about the local acceleration due to gravity near one of the outer planets and was corrected and embarrassed. It's easy to forget that gravitation is the result of many tiny things all pulling on each other, not just a few big and small things. I looked through the paper and didn't see anything about the radius of the planet candidate. I suppose it's quite difficult to determine it from so far away. Is a value known? If so, that would obviously give a good idea about the local g.
- Robotbeat 7y ago
  The radius is often not known. Radius is found most easily with transiting exoplanets, which are easy to detect but also only visible if you're lined up along the plane of the exoplanet's orbit. You can also possibly find it via imaging, but even then, since you can't directly resolve it better than a point light source, you're making assumptions about albedo that lead to a wide dispersion in possible radii. High resolution optical imaging would require a telescope roughly 1-2km in diameter. Pretty tough... and because of the glare of the star, would be nearly impossible to image with an interferometric (i.e. non-filled-aperture) telescope since the light gather power would be so low. However, astronomers are incredibly clever at pulling data out of tiny points of light, so there may be some way.
  - bmgxyz 7y ago
    Thanks for this, it's quite interesting. I have a friend who used to work in a lab doing super-resolution microscopy (i.e. beating the diffraction limit by various means) for use with bio/medical applications. Some of the techniques he told me about have to do with more or less taking lots of data from many images and assembling it all into something meaningful. I suppose what you're describing as "pulling data out of tiny points of light" is kind of the same thing. It's just that the scale is different.

matt123456789 7y ago

Most extrasolar planets that we have detected. It’s harder to detect the smaller ones, so we haven’t. Future space telescopes will have the equipment to help with this problem.

skykooler 7y ago

Note that this is the second planet found around Proxima Centauri. The first one is only 1.3 Earth masses and sits 0.05 AU away from the sun, which puts it in the potential habitable zone.

exdsq 7y ago
0.05 AU seems dangerously close to the sun?
- ceejayoz 7y ago
  Not for a tiny, weak star like Proxima Centauri. https://en.wikipedia.org/wiki/Proxima_Centauri_b https://en.wikipedia.org/wiki/Proxima_Centauri_b > The host star, with about an eighth of the mass of the Sun, has a habitable zone between ∼0.0423–0.0816 AU.
  - exdsq 7y ago
    I didn’t know that! Thanks :)