Timeline for What defines the radius of a ball of gas like Jupiter?
Current License: CC BY-SA 3.0
12 events
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| Jul 20, 2022 at 1:14 | comment | added | Oscar Lanzi | The "1-bar" criterion is also sometimes used to define planetary "surface" temperatures. See the discussion surrounding Venus in this answer. The "temperature" on Venus, as measured at the 1-bar level is deemed suitable for retaining water at that level as distinct from the rock "buried" beneath the hot, supercritical $\text {CO}_2$. | |
| Jul 7, 2016 at 15:57 | comment | added | Luaan | @SF. Fairly consistent as far as the planet itself is concerned (the difference between the equator and the pole radius is around half a percent), but not as far as humans are concerned - the difference is significantly larger than the above-sea-height of Mt. Everest added to the deepest depths of the Mariana trench. We're living all over that little "error", so to speak. | |
| Jul 7, 2016 at 14:46 | comment | added | Mark Adler | Earth isn't a decent sphere either. Most planets' radii are given as two numbers: equatorial and polar. For Earth, those are 6378 km and 6357 km respectively. That ellipsoidal description is sufficient for most purposes, but the real equipotential surface is more complicated. Bodies like Phobos require a shape model, but a triaxial ellipsoidal model isn't too far off for Phobos. 13 x 11.4 x 9.1 km. | |
| Jul 7, 2016 at 14:39 | comment | added | Mark Adler | A model I found shows 10 bar at 90 km below 1 bar, and 100 bar at 270 km below 1 bar. | |
| Jul 7, 2016 at 9:35 | comment | added | SF. | @Gusdor: At least Earth has a fairly consistent sea level. What about Phobos, which isn't even a decent sphere? | |
| Jul 7, 2016 at 8:10 | comment | added | Gusdor | I wouldn't worry about surface inconsistencies with any measurement method. Earth has mountains disrupting its radius after all. | |
| Jul 7, 2016 at 7:54 | comment | added | uhoh | I found the equation for scale height, but stopped when I realized I don't know any of the other values besides acceleration. I'm guessing that the atmosphere climbs from 1 bar to say 100 bar for example pretty fast, relative to Jupiter's large size? | |
| Jul 7, 2016 at 4:13 | comment | added | Mark Adler | I have no idea who is responsible for starting that convention. The rationale is that the surface of the Earth is at 1 bar, so we might as well make the surface of the gas giants at the same pressure. Though if we applied that logic to Venus, it would suddenly get bigger. | |
| Jul 7, 2016 at 4:11 | history | edited | Mark Adler | CC BY-SA 3.0 |
add sun
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| Jul 7, 2016 at 3:48 | comment | added | Erik | Not to be a smart ass, but where did this definition come from? Is it the same for the other gas giants? Thanks! | |
| Jul 7, 2016 at 1:48 | history | edited | Mark Adler | CC BY-SA 3.0 |
added 495 characters in body
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| Jul 7, 2016 at 1:37 | history | answered | Mark Adler | CC BY-SA 3.0 |