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22h
comment How do star densities work?
@userLTK: Yes, the Sun's radius and with it the luminosity increase over time. Wikipedia reference: arxiv.org/abs/0911.4872
Feb
2
comment Good textbooks for a descriptive astronomy course
I can concur, the newer edition covers now also Exoplanets and Protoplanetary discs. I saw it somewhere at my department, seems pretty good as intro on pretty much everything in astronomy & astrophysics. The math is pretty basic, so I guess the lecturer would be free to include some analytical mechanics. I don't see however where thermodynamics would play in, except for atmospheres and newer developments in cosmology.
Feb
1
comment Which planets have abundant amounts of photoluminiscent matter?
You can do transits in different bands and compare depths and widths. This is called transit spectroscopy. A reference is eso.org/sci/meetings/2014/exoelt2014/presentations/…, this team publishes nice papers about that. Emission spectro exists as well, but I agree with you that probably we wouldn't see anything from terrestrial bodies yet. Maybe even not with JWST.
Jan
31
comment Which planets have abundant amounts of photoluminiscent matter?
"so there is no information about exoplanets." Spectra?
Jan
30
comment Terminology: Is there a name for the points on the surfaces of tidally locked parent/satellite bodies that always face each other?
@Bironius Yes this makes perfect sense. I was just unsure whether you were aware of this. I don't know the answer however.
Jan
30
comment Terminology: Is there a name for the points on the surfaces of tidally locked parent/satellite bodies that always face each other?
Both bodies don't have to be facing each other. It is the less massive body, the moon or Hot Jupiter that is facing always with one side towards the more massive body, while this one keeps turning happily ever after at its own rate.
Jan
29
comment Why does the planet Saturn have numerous (62) moons compared to the rest of the planets in the Solar System?
Considering your last statement, it's actually the other way round. Saturns rings evolve dynamically over time and must spread out beyond the Roche limit. They thus would deliver material to the outer region where it can coalesce into moons or at least accrete onto them.
Jan
26
comment Hypothetical beyond Neptune far away planets orbiting the Sun
@MBR: Wise couldn't detect everything. It had a mass-semimajor axis window of undetectability exactly there where the ninth planet was calculated to be.
Jan
20
awarded  Tumbleweed
Jan
14
comment Method to determine the amount of reflected starlight necessary for an exoplanet to be visible from a given distance/angle?
Part of what you want to hear is the theory of radiative transfer (see wikipedia). It centers around a photon-counting equation to determine how much light of which wavelength an object emits. Solutions to this equation however cannot be written down in a straightforward way, they must be computed self-consistently using other equations and inputs (gases, light absorption & scattering properties). The other questions you had concern instrument effects here on Earth. You could split your question accordingly.
Jan
14
comment How unusual is the solar system?
@ConradTurner: Well if you want to go there: With the specifics given, even your number of $10^-{6}$ might be a very high estimate. In particular the quote "and there are few habitable planets that have anything more than pebbles orbiting them." that might another very high factor to this number, is simply unknown at this moment. The probability of all combinations together might be $10^{-12}$ (making it unique in the galaxy) or $10^{-4}$ (making it normal), we just don't know, and thus can't refute the hypothesis. It's a numbers game with unknown numbers.
Jan
14
revised How unusual is the solar system?
typos
Jan
13
revised Is atmospheric turbulence irrelevant for ExoPlanetary transits and radial velocity measurments?
added note that i googled
Jan
13
asked Is atmospheric turbulence irrelevant for ExoPlanetary transits and radial velocity measurments?
Jan
11
answered Why is it that we can"t feel how fast the Earth is moving?
Jan
11
answered How unusual is the solar system?
Jan
8
comment Do great spot like features favour appear in south hemisphere?
There's no physical reason to expect those storms preferably to appear on either of a planet's hemisphere. However there's the caveat that there is still no sufficient consensus on how to explain the longevity of Jupiter's Great Red Spot. That doesn't mean we can't explain it, it only means there are too many possibilites, and we don't know which one is true.
Jan
8
comment Where does Jupiter's gravitational force come from? Why don't Jupiters gasses fly away?
Jupiter has 320 Earth masses in Mass, this makes it harder for anything to escape his gravity well. It makes no difference if the mass is solid, fluid, gaseous, ...
Dec
19
comment If the Sun were bigger but colder, Earth would be hotter or colder?
@Carlos: As HDE said it depends on the precise values. Without pluggin in numbers you cannot know, as expansion and cooling have two competing effects on the luminosity.
Dec
19
comment Why can't gravity repel things?
@Jamie: Ah ok. However, are you interested in more detailed math-stuff? The "picture-math" can be found on wikipedia. The "math-math" I could provide.. somewhere between the upcoming holidays