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It's posited that this planet kept its atmosphere despite intense solar radiation pressure because it either moved into this orbit recently from a safer place,
by eloff 7y ago
It's posited that this planet kept its atmosphere despite intense solar radiation pressure because it either moved into this orbit recently from a safer place, or it had much more atmosphere to begin with. I wonder if maybe it just has a very powerful magnetic field that protects it, just like Earth's does.
That's the reason Earth has kept its atmosphere while Mars did not, despite the fact that Mars is twice as far from the sun.
- txtsd 7y ago> solar radiation Stellar radiation. Solar implies our own local star, Sol.
- thaumasiotes 7y agoMore intuitively, solar radiation would be radiation from the planet's local star, its sun. Radiation from our star would be stellar radiation. We're here; it isn't.
- deleted 7y ago[deleted]
- dragonwriter 7y ago“Sol” is the name of our star, not whatever star happens to be closest to a given planet.
- thaumasiotes 7y agoSo what? The name of those little points of light in the night sky isn't "stella", but they give off stellar radiation. It's solar radiation by reference to the concept of the sun, not by reference to an entry in an astronomical catalog somewhere.
- dragonwriter 7y ago> The name of those little points of light in the night sky isn't "stella" Well, yeah, the generic name for them is exactly that (well, in Latin, but that's also where Sol as the particular name for ours comes from.)
- thaumasiotes 7y agoIn terms of Latin, sol is just as generic as stella is. (Modulo the fact that there is only one sun.) If you want to object that "Sol" is the name of an individual star, and that "solar radiation" is named after that name, in spite of the capitalization, rather than deriving from the Latin word, then you can't really make your arguments based on what the words mean in Latin.
- dragonwriter 7y ago> In terms of Latin, sol is just as generic as stella is. (With the caveat that there is only one sun.) We can argue over whether the idea of a generic label for a class that by definition has exactly one member is coherent, but I don't think that's necessary: stars that aren't the sun are stella and aren't sol, whether you take the latter to mean “Aren't the single particular entity named ‘Sol'” or “Aren’t one of the members (of which there are exactly one) of the class whose members are designated ‘sol’”. There's a reason they are “extra-solar planets” and not “other-solar planets”.
- thaumasiotes 7y agoIt was a class with one member at the time Latin was spoken. It's the same class now, but with many members. Once you admit that the sun is an example of a star, "sun" becomes a deictic reference. Note that "Sol" is not the English name of our sun. We call it "the Sun", at the same time that we're happy to say that planets in other stellar systems have suns of their own. "Sol" is a name internal to academic astronomy, much like the name "bufo bufo" for what are actually called "toads".
- 7y ago
- duxup 7y agoEarth's magnetic field comes from a molten core / currents from it right? (someone correct me if I'm wrong, this isn't my area of expertise) Is an exoplanet that far out likely to have a molten core / maintain a magnetic field in some other way?
- eloff 7y agoIt's very close to its star, the comparison to Neptune is based on size, not its orbit.
- duxup 7y agoDOH my misunderstanding.
- samstave 7y agoThat leads me to the following question: is earth the onnly planet in our system which has a molten core or do they all have molten cores?
- jessriedel 7y agoI think all the rocky planets (Mercury, Mars, Venus) probably have molten cores, though it's pretty uncertain. The best evidence is for Mars. https://newatlas.com/mars-gravity-map/42430/ https://newatlas.com/mars-gravity-map/42430/
- logfromblammo 7y agoMercury probably has one from insolation and tidal forces from the sun. Venus might still have one thanks to its thermal insulation blanket. Earth and Moon flex each other with tidal forces, and Earth also has a much thinner insulation blanket. Mars might still have one, but its moons don't have much tidal influence, and its blanket is even thinner than Earth's. So if Mars still has one, chances are good that all the inner planets also have one. They would all be warmed some by radioactive decay, too. Io (vulcanism) and Ganymede (magnetic field) probably have layers of molten rock/metal in their cores, from tidal forces with Jupiter. Icy moons Europa and Callisto probably have a liquid water layer for the same reason.
- dwaltrip 7y ago> I wonder if maybe it just has a very powerful magnetic field that protects it, just like Earth's does. With an orbit of 1.3 days, I would guess that it is tidally locked, which I think would make it unlikely to have a strong magnetic field.
- cevn 7y agoWhy? Is it because the sun batters the same side of the field with radiation as opposed to distributing it evenly?
- genocidicbunny 7y agoBecause its far less likely that it has a rotating core due to being tidally locked. You need something like that to generate a planetary magnetic field.
- mgsouth 7y agoA tidally locked core would rotate once every 1.3 days, would it not? [edit: Never mind. I think. Apparently it's rotation of two layers of core relative to each other that generates the field. However... since the plant is so close to its star, what would the effects be of a core rotating in a strong stellar field?]
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- mgsouth 7y agoDelayed edit: Yes, apparently tidally-locked planets can have a surprisingly large magnetic field. Evidently the major reason for planetary fields is convection, not rotation. ([0] cites [1]) However, I believe there are also homopolar [2] generation effects due to the star and the planet's (tidally locked) rotation. [3] looked at fields caused by convection due to tidal flexing. [4] talks about magnetic interactions between stars and close planets. [0] https://www.quora.com/How-does-the-magnetic-field-of-a-star-.. https://www.quora.com/How-does-the-magnetic-field-of-a-star-.... [1] “Energy flux determines magnetic field strength of planets and stars”, U. R. Christensen et al, Nature vol 457, pages 167–169 [2] https://en.wikipedia.org/wiki/Homopolar_generator#Astrophysi.. https://en.wikipedia.org/wiki/Homopolar_generator#Astrophysi.... [3] https://exoplanets.nasa.gov/news/217/earth-like-exoplanets-m.. https://exoplanets.nasa.gov/news/217/earth-like-exoplanets-m.... [4] https://www.youtube.com/watch?v=HjfOdjpNZHo https://www.youtube.com/watch?v=HjfOdjpNZHo (Talk by Evgenya Shkolnik, part of Short Course on Magnetic Fields: A Window to a Planet's Interior and Habitability at the Keck Institute for Space Studies at Caltech on August 12, 2013)
- chunger 7y ago>That's the reason Earth has kept its atmosphere while Mars did not How would you explain Venus having an atmosphere while not generating a magnetic field?
- mbell 7y agoVenus has a very thick, hot and high pressure atmosphere. This both makes it hard to blow off and gives it a strong ionosphere which acts as a stand in for a magnetosphere.
- logfromblammo 7y agoMars is also much lighter than Earth. Venus is less massive than Earth, but not by much. Even so, Venus has had most of its hydrogen stripped away over time. Thanks to its high temperature, that also includes hydrogens formerly bound in heavier molecules, like water. The process continues, very slowly. Venus is still losing its hydrogen and helium, more quickly than Earth. One terraforming plan for Venus involves shipping magnesium hydride there, decomposing it, and using both the H2 and the Mg to react with all the CO2 in the atmosphere to make soot, chalk, and water, reducing the surface pressure to about 3 atm of mostly N2. Nothing works without shipping hydrogen to Venus. But once it's there, it will take many millions of years to get stripped away again, because that happens so slowly, over geologic time scales.
- whatshisface 7y agoHow long could a constant supply from the asteroid belt be kept up?
- jandrese 7y agoI guess it depends how much magnesium hydride you find or can make there. It's a very long trip from the belt to Venus though. And honestly, if you have the resources to mine global amounts of magnesium hydride from the belt and ship them all the way to Venus you have the technology to build a nearly unlimited number of space colonies that would be much much nicer to live on than even a terraformed Venus.
- PorterDuff 7y agoI'd have to look it up, but perhaps getting smacked by an outer planet (to make the moon) delivered a lot of the atmosphere's contents.