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Questions tagged [interstellar-medium]

Questions about the gas that lays between stars in galaxies.

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Deep space radiation distribution

What frequency distribution law applies to a random point in deep space that is assumed to be far away from any particular source of radiation. Can it be expressed by some form of Plancks/Bose-...
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2answers
53 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 ...
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1answer
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How dark would the sun become if we traversed a Bok globule?

Bart Bok gave his name to dust clouds of 2-50 solar masses, which by their darkness may be 100 times more frequent than telescopes can detect. If the solar system traversed a Bok Globule, how dark ...
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What are the different values used/found for the slope of the turbulent power spectrum?

I'm a simulator, so forgive me if this question is a bit biased towards theory, I'm also interested in the observational side if anyone can comment. So when we model a turbulent medium (like the ISM) ...
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1answer
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carbonaceous content of galaxies?

There is a phrase in a Science Daily article which appears to be wrong: The Milky Way has a very high content of carbonaceous dust, which has been shown to be very rare in other galaxies. Is there ...
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2answers
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Why is the Warm-Hot Intergalactic Medium (WHIM) so hot, and what is “collisionless shock heating”?

The Phys.org article Researchers find last of universe's missing ordinary matter says: Ordinary matter, or "baryons," make up all physical objects in existence, from stars to the cores of black ...
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1answer
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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 ...
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1answer
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Potential formation mechanisms of the interstellar asteroid 'Oumuamua

NASA recently discovered 'Oumuamua, an interstellar asteroid that appears to have a very elongated shape, unseen in solar system asteroids. What physical mechanisms, in the progenitor stellar system ...
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1answer
56 views

Would Bussard Ramjets work in other places in or near the galaxy? [closed]

Sorry if this this doesn't really fit this forum, but WorldBuilding does not like questions like these. I cannot find the minimum density of hydrogen a Bussard ramjet (an interstellar ship propelled ...
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1answer
84 views

Metals and dust locked into planets

I wonder what is the contribution of metals and dust locked into planets, with respect to the amount in the interstellar medium (ISM). In other words, when we measure the metallicity and the dust mass ...
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1answer
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Does the sun blow a bubble into the interstellar medium?

I once read that the solar wind is more or less blowing a "bubble" into the interstellar medium. However, the numbers I found while trying to verify this don't give me a clear picture yet: The ...
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Can the shape and fluctuations of the heliopause be attributed to specific nearby stars and clusters?

The heliopause is where the Solar wind is counter balanced by the particle winds from other stars. This boundary seems to not be spherical and also to fluctuate in shape. Can the shape of the ...
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Why isn't interstellar medium pulled in towards nearest massive object?

How does the ISM resist gravity? That's the only force acting on it, and all other particles seem to collect together to form stars. What makes the ISM so special among other particles?
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Is the expected time for a star in an elliptical galaxy to collide with another star less than the average age of elliptical galaxies?

According to the Wikipedia article Elliptical galaxy, elliptical galaxies have a much lower concentration of gas between the stars than spiral galaxies. I know that until the gas is below a certain ...
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Free-fall time of circumgalactic gas as function of galactocentric distance

My question applies to gas falling in toward a galaxy from the circumgalactic or intergalactic medium, under the influence of gravity from the central galaxy itself as well as the overall dark matter ...
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For chemical reactions occurring in the interstellar medium, which involve metal-ions, will the metal ions be solvated or not?

Usually, metal-ions in terrestrial chemistry will be solvated - either by gas-phase solvent molecules or by liquid-phase solvent molecules. But the interstellar medium (ISM) is never in local ...
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Do liquids exist in the interstellar medium?

Am not asking about planetary/meteorite surfaces and am restricting myself to the interstellar medium edit: by interstellar medium I mean, the following: "Interstellar medium (ISM) is the matter ...
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131 views

Could there be massive charged “rivers” in interstellar space?

Some suggest that there might be currents of charged particles moving at 0.98c in interstellar space. Since this is tainted by association with the crack “Electric Universe” cosmology, my first ...
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Explanation of the isochoric and isobaric instability conditions of interstellar medium gas clouds [duplicate]

The question Why are there no ISM clouds with temperatures between 100 and 6,000K? has an accepted answer of the form: Let $n$, $T$, and $x_i$ be the number density of hydrogen, the temperature of ...
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Why are there no ISM clouds with temperatures between 100 and 6,000K?

In the interstellar medium, there are several different diffuse phases of gas, distinguished by their density and temperature. Specifically, the cold neutral medium has temperatures from ~50-100 K and ...
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1answer
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Examples of astrophysical objects NOT in virial equilibrium?

Astronomers always talk about astrophysical objects being in virial equilibrium (e.g., a stellar system, or a disk of gas within a galaxy, etc.). But I never hear about thermodynamical equilibrium. ...
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2answers
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Would a spaceship have to evade interstellar clouds?

Apparently, there are clouds of "dust" between the stars. Would a starship have to fly around those clouds, trying to find "tunnels" between clouds, or are the interstellar clouds harmless for a ...
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What is the word for space that is in the solar system, but outside the heliopause?

Wikipedia says the definition of interplanetary space is the region dominated by the interplanetary medium, which extends out to the heliopause where the influence of the galactic environment ...
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Virial coefficient when computing dynamical mass enclosed by a rotating galactic disk of gas

Suppose I have a large thin disk of rotating gas in a galaxy -- the disk has a maximum inclination-corrected $V_{max}$ and a maximum radial extent of $R_{max}$ corresponding to that $V_{max}$ ...
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5answers
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How cold is interstellar space?

The vastness of space brings me a sense of chilliness even though I have never experienced it, although I wish to. Just how cold is interstellar space (on average)? How is this even measured? I mean ...
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1answer
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Population of excited H levels in a Strömgren Sphere

In chapter 2.2 of Astrophysics of Gaseous Nebulae and AGN Ostriker and Ferland claim that, as far as ionization is concerned, one can assume all atoms to be in the ground state in a Strömgren Sphere ...
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What would the night sky look like if the interstellar medium didn't exist to absorb or block light?

I was curious about how much brighter it would be and how much further we could see.
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Does a self-gravitating gas necessarily develop turbulence?

Though we may still doubt the exact driving mechanism of turbulence in each particular case (ISM, MC, circum-BH/-stellar discs, atmospheres...), can I say that in a sphere of dark matter particles no ...
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1answer
188 views

Why dust is optically thin in Far Infrared wavelengths?

What is the actual meaning of the statement 'Dust is optically thin in the Far Infrared (FIR) over most of the Galaxy'? Kindly Help
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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 ...
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1answer
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What is the distribution of organic compounds in the Milky Way Galaxy?

I imagine the answer is unknown for the entire galaxy, but I would appreciate a notion of the scales and locations of regions where astronomers have ventured at least a guess to the distribution of ...
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2answers
883 views

Lack of objects between heliopause and Oort cloud?

If we take a look at a logarithmic scale of the Solar System, there appears to be a large gap between the heliopause and the Oort cloud: Why is that? There are some objects in the gap, but why are ...
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2answers
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Dust mass-loss rate from a massive star given a set of parameters?

I've been looking for examples at how mass-loss rates are determined. I'm studying a circumstellar dust shell ejected from a Wolf-Rayet star. I have some parameters like, expansion velocity of the ...
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Can dark matter decrease the Jeans length?

I am wondering if there are any models of interstellar cloud collapse out there which take dark matter into account. If dark matter has local perturbations or density fluctuations, then that may be ...
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1answer
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Why is [O III] a good density probe in interstellar medium?

According to Draine in his book "Physics of the interstellar and intergalactic medium" (page 210/211) and Caltech [O III] line ratio's (amongst others) are a good density probe, but I cannot really ...
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How would vehicles travel through the interstellar medium with its such low density?

I've heard from a number of different places that the density in the interstellar medium can have an average of 1 atom per centimeter cubed. Perhaps I have a wrong understanding of what 'nothing' is (...
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3answers
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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 ...
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Why is the interstellar medium so hot?

On this link, it states the following: "large assemblies of galaxies that are permeated by even larger amounts of diffuse gas. With temperatures of 10 million degrees or more". How are these ...
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Do we live in a galactic bubble?

I have heard a certain statement, which can be summarized succinctly into "we live in a local bubble", implying that solar system is located in an intestrellar dust underdensity region. This region ...
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1answer
420 views

Sources of Turbulence in the ISM

What sources of turbulence exist within the Interstellar medium (ISM)? Which ones are physically the most important for newly forming stellar systems?
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How does interstellar matter density vary?

Answer to my question partially answers this one, about density of intergalactic matter and matter within galaxy: But it is mostly a hot, ionized void. How void? The density of the intergalactic ...