Questions tagged [gas]
Questions regarding matter in its gaseous state, and how it behaves in astronomy (e.g. forming stars in giant molecular clouds).
31
questions
6
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1answer
50 views
Why is molecular hydrogen (H2) so difficult for astronomers to detect?
I am reading a great deal about the various forms of hydrogen throughout the universe, and I keep reading that 'molecular hydrogen is notoriously difficult to detect', and other sentiments along those ...
0
votes
1answer
66 views
How do they know the newly-spotted gas near the center of our galaxy is molecular without knowing what gas it is?
Phys.org's Mystery gas discovered near center of Milky Way links to Teodoro et al 2020 in Nature Cold gas in the Milky Way’s nuclear wind who's abstract is shown below.
Question: My reading of the ...
3
votes
1answer
81 views
Surface of the Sun, or Jupiter, etc [duplicate]
I keep hearing and reading statements that refer to the "surface of the Sun" (how hot the surface of the sun is) or the "surface of Jupiter" (when the Shoemaker comets hit Jupiter)....
3
votes
1answer
41 views
Galactic winds/outflows: why and how are they detected via blueshifted absorption lines in spectra?
I know that galaxies can eject gas due to supernovae, accreting black holes, etc. These galactic "winds/outflows" are often defined/detected observationally using blueshifted absorption ...
2
votes
2answers
65 views
How does gas in accretion disks of supermassive black holes create orbital torques on smaller black holes within the disks causing them to migrate?
This answer to What enhances the capture and merge rates of pairs of small black holes orbiting around supermassive black holes? links to Migration Traps in Disks Around Supermassive Black Holes which ...
6
votes
1answer
3k views
Starting a fire in a cold planet that was full of flammable gas
What would happen to a cold planet that has a large amount of flammable gas, like Neptune, if we throw some fire into it? Will it burn, or would the flame be extinguished due to the cold?
3
votes
1answer
85 views
Why are Bok globules so cold?
I have recently read a bit a out Bok globules. One thing, that is repeatedly emphasised is that they are among the coldest objects in space, with a temperature of ~3 K.
Why is that so? Naively, I ...
0
votes
1answer
95 views
Can we get the gas compositions from a gas planets? [closed]
Is it possible to get some gases like hydrogen from gas planets (Saturn, Jupiter, Uranus or Neptune)?
1
vote
1answer
84 views
Is there a plausible causal mechanism to explain why the Sun would be heating up faster/ sooner than we thought? Question for a novel [closed]
I am writing a novel about what it will be like on earth 500 or so years before the death of our Sun. The Sun is heating up gradually and one day that will negatively affect life on Earth. I know that ...
3
votes
2answers
212 views
What is the diffuse ionized gas?
I've been trying to find a clean definition what people mean by when they talk about diffuse ionized gas in the interstellar medium, but I couldn't find anything so far.
Apparently it's supposed to be ...
2
votes
1answer
566 views
What are the so called clouds of dust and gas made of?
We constantly read about "clouds of dust and gas" surrounding a (or being the initial state of a) star, but what elements constitute such dust and gas?
2
votes
1answer
57 views
How is interstellar gas density mapped from GAIA data?
I found the image below in Space.com's article This 3D Color Map of 1.7 Billion Stars in the Milky Way Is the Best Ever Made.
The caption for this image reads:
The Gaia spacecraft gathered ...
3
votes
1answer
171 views
What would the pressure and temperature of gas be, right above Jupiter's gas/liquid boundary?
Older pages like this "Exploration of the Solar System" course page describe the transition as being a few hundred kilometers down.
More recent findings seem to put the boundary deeper. See
The ...
2
votes
1answer
509 views
Would a spacecraft just go “through” a gas giant?
From my understanding of the word gas giant, it is a planet composed of entirely a gaseous atmosphere, and so planets Jupiter and onwards fall in this category.
That being said, what would stop a ...
0
votes
1answer
240 views
What is the condition for the number density of a gas to be ultra-relativistic or non-relativistic and degenerate or ideal
What is the condition for the number density ($n$) of a gas to be ultra-relativistic or non-relativistic and degenerate or ideal?
I found problems in this subject when I was reading about White-...
2
votes
2answers
119 views
Is this gas cloud or lens effect?
I was going through the zoomable image of Milky way and after zooming to this particular location, we can see a reddish area on the left side of a probably large star. Here is a screenshot I took ...
4
votes
1answer
272 views
Are gas giants supported by thermal pressure?
I've heard gas giants are supported because there is an equilibrium between thermal pressure and gravity. That is, if Jupiter were to suddenly begin compressing, temperatures would increase to the ...
3
votes
1answer
142 views
Why is the “green” comet C/2014 Q2 (Lovejoy) red in this picture?
In this nice NYTimes 'survey article' "Our Vast Solar System
and Its Many Explorers" there is a NEOWISE image of Comet C/2014 Q2 (Lovejoy). See here also.
The NASA description of the image says:
...
1
vote
1answer
873 views
How to show that the Jeans Criterion for Mass, Radius and Density are equivalent?
The gravitational collapse of a gas cloud can be described by the Jeans Criterion for mass, radius and density of the gas cloud, which is (c stands for cloud):
$$M_J = (\frac{5kT}{G \mu m_H})^{3/2} (...
1
vote
1answer
196 views
How do astronomers detect gases that are in the atmosphere of exoplanets?
Exoplanets are planets that are located outside our solar system - whether that be orbiting a star or drifting past one. Now, the closest star to us is Alpha Centauri which is just over four light-...
1
vote
1answer
858 views
What is the equation of state for a relativistic fluid/gas?
Say we have a relativistic fluid/gas, as we have in some astrophyical systems.
Now let us write:
$e$ - energy density in the fluid's rest frame.
$P$ - pressure in the fluid's rest frame.
$n$ - ...
3
votes
0answers
73 views
How do people derive ionized gas mass from optical emission lines in a galaxy spectrum?
Suppose you had an optical spectrum of a galaxy, and you unambiguously detected emission lines from cooling ionized gas -- both forbidden lines like [O II] 3727AA and [O III] 4959,5007AA, as well as ...
12
votes
2answers
4k views
Why argon instead of another noble gas?
I noticed that the atmospheres of Earth and Mars have a little bit of argon in them (1% to 2%). I checked Venus, too, which has 0.007% argon, but that's still more than any other noble gas in the ...
2
votes
1answer
360 views
When is it a good aproximation to consider a star to be an ideal gas?
I am currently taking a first course on stellar astrophysics, and I noticed that in some cases we use the ideal gas equation of state for stars, so we also use $\gamma =5/3$. Of course it can only be ...
5
votes
1answer
76 views
Gas halo of our Milky Way Galaxy
This question relates to a diffuse hot gas halo of our Milky Galaxy. I've read that there is a hot diffuse halo of gas surrounding our Galaxy (NED, Caltech)
I was wondering why such a halo can exist? ...
2
votes
1answer
70 views
What is a typical value for core-to-star efficiency?
I was reading Unfolding the Laws of Star Formation: The Density Distribution of Molecular Clouds by Kainulainen et al., which discusses star formation rates and efficiencies.
One variable used is $\...
2
votes
1answer
3k views
Can asteroids contain atmosphere?
Gas is abundance in the universe, can a massive asteroid draws in these gas forming a thin atmosphere?
9
votes
1answer
20k views
What will happen when landing on Jupiter?
Jupiter is a gas giant, so landing on it will not be like landing on Earth, our Moon or Mars etc., as it does not have a solid surface like these.
If we have a hypothetical spaceship or probe landing ...
2
votes
1answer
224 views
Beta profile fit of Virgo cluster gas?
I'm looking for the parameters $r_c$, $\rho_0$ and $\beta$ in a $\beta$-profile fit of the Virgo cluster's ICM density. I just can't find a reference for it. Unlike for Coma (Abell 1656) where it's in ...
4
votes
1answer
173 views
What is the physics of a gas mass subject to gravity in space?
There are many formulas for atmospheric pressure on earth, but how does gas behave in free space?
I am thinking about why stars form. I am guessing that the gas density will influence pressure, as ...
16
votes
3answers
3k views
What is the difference between gas and dust in astronomy?
Is there a strict difference between gas and dust?
In Earthly environment most things become gaseous if heated enough. The temperature of interstellar medium seems to range mostly between 10 and 10 ...
