Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: CliffordK on 29/08/2012 20:50:19
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Would we be able to detect planets the size of Jupiter that were more than one lightyear away from their parent stars? From our own Sun?
I presume Jupiter and Saturn produce quite a bit of their own internal heat so that they would have a weak IR signature. Would that be enough?
Dwarf planets the size of Mercury, or our moon could be close to background temperature. Even larger planets the size of Earth would be mighty chilly.
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I think a Jupiter size "planet" one LY from the nearest star could be considered free roaming I am open to opinions as to whether its self generated heating would render it visible in the IR I am inclined to believe it would not.
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Bring on the James Webb IR space telescope!
Something like the Kepler telescope may be able to put an upper bound on the number of free-roaming planets - they would affect the star's light very differently than a planet in a close orbit.
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The problem is very similar to detecting brown dwarves but would be more difficult as a planet mass object will have run its course in producing heat from gravitational collapse and will only have the heat generated by radioactivity hence a surface temperature only a little above the CMBR.
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I'm not sure a large planet would drop to background temperatures, but perhaps the temperatures would be as low as 20K. The outer planets have a complex atmosphere, but they all seem to be somewhat warmer than their respective moons.
Or, is what we're seeing as "background radiation" actually the temperature signatures of matter?
I suppose fissile material would generally be equally distributed between planets, moons, an asteroids (is that part of what causes the CMBR?) So for a free roaming planet to be distinguishable from the background, it would need an additional heat source other than fission.
Anyway, it would seem as if there could be a great deal of non-luminous matter out there that isn't necessarily WIMPS.
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I'm not sure a large planet would drop to background temperatures, but perhaps the temperatures would be as low as 20K. The outer planets have a complex atmosphere, but they all seem to be somewhat warmer than their respective moons.
Or, is what we're seeing as "background radiation" actually the temperature signatures of matter?
I suppose fissile material would generally be equally distributed between planets, moons, an asteroids (is that part of what causes the CMBR?) So for a free roaming planet to be distinguishable from the background, it would need an additional heat source other than fission.
Anyway, it would seem as if there could be a great deal of non-luminous matter out there that isn't necessarily WIMPS.
"(is that part of what causes the CMBR?)" On this sidenote: No, the CMBR is fossil radiation from 300k years after the big bang. What was ultraviolet radiation being emitted and reabsorbed in an opaque plasma dominated universe was finally emitted and not reabsorbed as the universe cooled, electrons stuck to nuclei, and the universe became mainly transparent. That last batch of radiation from the poetically named surface of last scattering has been travelling and stretching for billions of years - we now observe it massively redshifted as microwave radiation a/o as the background temperature of empty space