Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Pseudoscience-is-malarkey on 17/03/2016 08:05:35
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We see and read about it a lot in fiction: an Earth like moon orbiting a gas giant. Would the radiation of the gas giant make habitability impossible? Gas giants, because of their immense gravity, undoubtedly would produce radiation, just like the four giant planets here in Sol.
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Why not? The Earth orbits an - albeit gigantic - gas giant!
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Gas giants undoubtedly would produce radiation
Any object above absolute zero undoubtedly produces electromagnetic radiation. It's not inherently dangerous.
Earth's orbit around the Sun has a "black body" temperature of about -15C; the greenhouse gases in our atmosphere bring this up to a more habitable positive temperature.
So an Earth-sized moon orbiting a gas giant could be at a comfortable temperature provided it's temperature is in this "goldilocks zone" with liquid water.
Probably this moon would be tidally locked to the gas giant - so one side would get a normal day/night cycle without ever seeing the gas giant, while the other side would have the gas giant fixed in the sky, with the star just appearing in the morning and evening (the noon would be dark, but perhaps heated by infra-red radiation from the gas giant).
Gas giants, because of their immense gravity, undoubtedly would produce radiation
This does not necessarily follow. Static gravity by itself does not produce radiation.
One way this may occur is that gas giants may have a core of compressed metallic hydrogen, which could produce a strong magnetic field. Such a magnetic field could capture energetic particles from the solar wind, which may be nasty if the moon orbited within the radiation belts, and did not have its own protective magnetic field.
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Why not? The Earth orbits an - albeit gigantic - gas giant!
This is true, but we orbit our "gas giant" at a relatively far distance. Orbiting a gas giant would obviously put the world in extremely close proximity, within the radiation zone of which no natural ozone layer would be able to propel, I think. For this, I cannot see life naturally evolving there. But I am an historian, not a scientist.
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There is much talk of the "goldilocks zone" but the Earth with a black body temperature of -28 degree C must be outside it then not capable of supporting life.
Is our definition of the goldilocks zone wrong not taking in the insulating effect of the atmosphere
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Is our definition of the goldilocks zone wrong not taking in the insulating effect of the atmosphere?
It is already defined fairly broadly. Around a Sun-like star, astronomers define this zone as around 0.5 to 3 Astronomical Units (AU).
This takes in Venus and Mars. If Mars had a thicker atmosphere, it might be habitable by humans in shirt-sleeves; if Venus had a thinner atmosphere, it too might be habitable.
See: http://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates
This article suggests that habitable moons of gas giants may outnumber habitable planets, given the statistics of planets we have been able to detect so far. But maybe that reflects the limited sensitivity of our current techniques; gas giants are easier to spot than small rocky planets...