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44 votes

Why is Uranus called a "green planet"?

I think your issue is linguistic not astronomical. The way a language cuts up the space of colours into discrete names is varies strongly from one language to another, and even from one dialect to ...
James K's user avatar
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32 votes
Accepted

Why is it impossible to infer the surface temperature of Venus by spectroscopy observation from earth?

The important difference is that the word "surface" has a different meaning depending on whether we're talking about the Sun or Venus. When we say "the surface of the Sun," we ...
Tanner Swett's user avatar
23 votes
Accepted

Is Earth's Atmospheric Thickness Related to Cosmic Ray Radiation?

It won't be (and isn't) zero. To see that, you want the plot on a logarithmic scale. Thus there isn't really a question to answer. The attenuation of cosmic rays will follow some exponential decay ...
ProfRob's user avatar
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18 votes

Why is Uranus called a "green planet"?

This answer looks into why Uranus is "green" or at least greener compared with Neptune's blue. Both planets have similar atmospheric compositions and would ordinarily be expected to show ...
Oscar Lanzi's user avatar
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18 votes

Why is it impossible to infer the surface temperature of Venus by spectroscopy observation from earth?

I think the problem is that spectroscopy at visible and infrared wavelengths simply can't penetrate the thick atmosphere of Venus. Thus the information comes from much higher in the atmosphere and not ...
ProfRob's user avatar
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11 votes
Accepted

Is there a formula for calculating surface temperature of a rocky world based on atmosphere and solar input?

Guillot et al. 2010 give a comparatively simple solution (their Eqn. 27) for a double-gray purely radiative atmosphere. It reproduces the equilibrium temperature in the optically thin limit. Robinson &...
AtmosphericPrisonEscape's user avatar
9 votes

Acetylene at Uranus? What's JWST's evidence and current thinking of how it's possible?

I think part of the issue here is that you seem surprised to learn that JWST detected acetylene in the atmosphere of Uranus, as though this is both unexpected and merits a certain amount of skepticism ...
Peter Erwin's user avatar
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9 votes

Why is Uranus called a "green planet"?

This is just a mere illusion. In reality, the peak wavelength is actually between green and blue, that is slightly cyanish/turquoise. The reason this happens is because the atmosphere of Uranus ...
Arjun's user avatar
  • 1,474
8 votes
Accepted

What will it take to start measuring the rotation rate and direction of exoplanets? Which instrument(s) current or future are most likely to do it?

The first exoplanet to have its rotation period measured was Beta Pictoris b in 2014. This was done using the Cryogenic highResolution InfraRed Echelle Spectrograph CRIRES located at the Very Large ...
sno's user avatar
  • 1,455
7 votes

Why is Uranus called a "green planet"?

A convenient pattern Uranus’ color is somewhere between green and blue. Since a lot of space trivia is in the purview of elementary education, and since patterns are useful for memorizing, it’s ...
Spencer Joplin's user avatar
6 votes

Acetylene at Uranus? What's JWST's evidence and current thinking of how it's possible?

A compilation of the known compositions of the gas giant planets (by number density), compiled from several sources indicated in the table, is given Lodders 1. References cited in the table [2-6] are ...
Oscar Lanzi's user avatar
  • 1,141
6 votes

Why is Uranus called a "green planet"?

Although both Uranus and Neptune exhibit a color palette ranging from deep blue to pale green, there is a prime difference in the atmospheric composition which determines the color difference. In the ...
Nilay Ghosh's user avatar
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5 votes
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When did Venus reach approximate radiation equilibrium?

If we assume that energy transport in atmospheres happens purely via radiation, then we can estimate a simple adjustment time to an exchange of exterior forcing factors (change in mean solar angle, ...
AtmosphericPrisonEscape's user avatar
5 votes
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Why are heavier hydrocarbons not present in lower part of Uranian atmosphere?

Methane is more abundant in the thermosphere and the stratosphere. On the stratosphere, the Wikipedia article you cite says The most abundant stratospheric hydrocarbons after methane... Also note ...
ProfRob's user avatar
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4 votes
Accepted

What is the concentration of molecular oxygen in the Martian atmosphere?

The Sample Analysis at Mars (SAM) in Curiosity rover measured the air of Gale Crater and analyzed its composition: 95% by volume is carbon dioxide (CO2), 2.6% molecular nitrogen (N2), 1.9% argon (Ar), ...
Nilay Ghosh's user avatar
  • 4,695
4 votes
Accepted

Carbon dioxide on terrestrial planets

It's very stable. Once created, it takes a lot of work to convert it into something else. Most other organic compounds have greater potential energy and are unstable on geologic timescales. The ...
BowlOfRed's user avatar
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4 votes
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When did Venus get as hot as it is now?

According to current models and computer simulations, Venus was a water world many billion years ago but due to the close proximity to it's host star, Sun or Sol, the water was Photocatalytically ...
Arjun's user avatar
  • 1,474
3 votes

Why are heavier hydrocarbons not present in lower part of Uranian atmosphere?

No knowledge on the subject, but I'd venture from looking through that article that it could well be the same reason lighter $O_2$ has peak concentrations in the troposphere on Earth, while heavier $...
JeopardyTempest's user avatar
3 votes
Accepted

Meteor visibility from two locations

In short, it is depended on the height of the meteor and the separation of observers. This is a rough sketch of the situation you are describing. There are 2 observers on Earth with a separation of $\...
Polaris5744's user avatar
3 votes

How does Titan maintain its atmosphere?

Wikipedia has a section addressing this question that hasn't been covered by the other answers. The summary is that the disparity between the atmosphere of Titan and similarly sized objects is not ...
JanKanis's user avatar
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3 votes

Trying to identify what I saw in the sky

Sorry, but my answer may be a little speculative I used Stellarium to find out where and what exactly it was, 12:45 AM on Saturday August 12th in the center of Nantucket Island Massachusetts. There ...
Arjun's user avatar
  • 1,474
3 votes

Meteors arriving to a planet's atmosphere?

The assumption of an atmosphere with nearly no wind is difficult to find or create - but let's assume we find such body. Gravity works on solid particles, and assuming that they are denser than the ...
planetmaker's user avatar
  • 19.9k
3 votes

Meteors arriving to a planet's atmosphere?

Yes, the material (dust and gas) stays in the atmosphere, at least for a while. Larger particles of dust will tend to fall, but are strongly affected by turbulence in the lower atmosphere. Water and ...
James K's user avatar
  • 125k
3 votes

The consequences and the mechanisms of a shift of the Earth away from the sun

Your idea of a planetary-mass black hole is on track. The real challenge here is that the black hole only gets one chance to change the orbit as it passes through the solar system. It would definitely ...
Mark Foskey's user avatar
  • 3,916
2 votes

What is the concentration of molecular oxygen in the Martian atmosphere?

Wikipedia xites Atmospheric Evolution on Inhabited and Lifeless Worlds giving this composition: ...
James K's user avatar
  • 125k
2 votes

Trying to identify what I saw in the sky

Were you looking NE? The Pleiades were just above the horizon at 12:45am. If not that, then unlikely to be any astronomical phenomenon.
ProfRob's user avatar
  • 155k
2 votes

What stops terrestrial planets from becoming watery gas giants with water vapour atmospheres?

The terrestrial planets formed in their final configurations over the course of a hundred million years or so. The collision that formed the Moon probably occurred about 30-50 million years after the ...
ProfRob's user avatar
  • 155k
1 vote

Which of the blocked radiation windows will (mostly) open if one where to observe from the surface of Mars, instead of the Earth?

Question 1: From Tokunaga (2000):The major atmospheric absorbers [in the infrared] are H2O [and OH], CO2, N2O, CH4, and O3. Question 2: X- and gamma rays: These would still be strongly attenuated even ...
giardia's user avatar
  • 2,098
1 vote

Does rotation on their axis cause winds in gaseous planets?

It is not true. What makes wind actually be wind is that it is moving relative to something else. On earth, that something else may be you, but on a gaseous planet the only "something else" ...
Mark Foskey's user avatar
  • 3,916
1 vote

Can IR sensitive cameras read signals from Venus's surface emissions?

@JamesK's answer is excellent. I just want to add another, more recent observation, with photos. In the case of Venus, does any of it's 800 degree surface temperature generated IR make it through it'...
uhoh's user avatar
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