Questions tagged [interstellar-medium]

Questions about the gas that lays between stars in galaxies.

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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 ...
LocalFluff's user avatar
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Why isn't most hydrogen in the universe molecular (diatomic), instead of atomic (monoatomic)?

Similar questions have been asked before; but, why? Is the monoatomic hydrogen left over from the Big Bang? And hasn't had the opportunity to collide with other hydrogen atoms yet? Or are hydrogen ...
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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?
Max's user avatar
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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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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 ...
SF.'s user avatar
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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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Is oxygen an alpha element?

Type II (core-collapse) supernovae occur shortly after star formation and enrich a galaxy with $\alpha$ elements such as O, C, NE, Mg, Ca and Si. On the other hand, Type Ia supernovae occur on a more ...
quantumflash's user avatar
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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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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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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 ...
Phiteros's user avatar
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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 ...
Sir Cumference's user avatar
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Gravitational waves and gamma ray burst: how were the error bars determined for this speed of gravity calculation? Was $H_0$ used?

This newly updated answer to How precise are the observational measurements for the speed of gravity? and this answer to How is the most accurate value of 𝐺 measured? cites the November 2017 arXiv ...
uhoh's user avatar
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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 ...
Alexey Bobrick's user avatar
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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 ...
uhoh's user avatar
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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 ...
dualredlaugh's user avatar
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Can circumstances exist such that as seen from some solar system all stars are obscured?

I am mostly active on Physics Stack Exchange but a question occurred to me that I think is best submitted here. This question is about a thought experiment: whether the circumstances of the intended ...
Cleonis's user avatar
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Why does dust affect UV light more severe than it affects X-rays?

My supervisor told me that the UV photons emitted from AGN are heavily affected by ISM (dust extinction), but not X-rays, as described in Extinction - a powerful discriminator of dust size. Since X-...
Jack the Ranger's user avatar
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Interstellar Dust properties

While practicing for an upcoming examination, I ran into this problem: Which of the following best describes dust grains in the interstellar medium: They are a few hundred nanometers in size (size ...
Kraftsman's user avatar
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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.
Pulchritude's user avatar
6 votes
1 answer
127 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 ...
user avatar
6 votes
2 answers
621 views

Why is blue light extincted more strongly than red?

We know that blue light suffers extinction more strongly than red (examples include ISM, atmosphere etc.), but why? Is it a property of the shorter wavelength itself? Can someone provide a conceptual ...
Astroturf's user avatar
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Speed of light through the ISM and Wavelength

Articles written about fast radio bursts describe the signal's short-wavelength components arriving before its longer-wavelength components, suggesting energy-dependent time delays in the interstellar ...
Sam's user avatar
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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 ...
DarkDust's user avatar
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How do we estimate the amount and distribution of Helium in interstellar and intergalactic space?

Quoting from wikipedia: Helium ... is the second lightest and second most abundant element in the observable universe (hydrogen is the lightest and most abundant). It is present at about 24% of the ...
steveOw's user avatar
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Do pulsar beams interact with the interstellar medium?

Pulsars are rotating objects that emit a beam in a direction that is not aligned with the axis of rotation. Because of this, we see them as a periodic pulse. If the beam isn't towards us, we don't see ...
usernumber's user avatar
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How much of a molecular cloud can end up as "starstuff"?

Stars form within molecular clouds. These clouds can be up to 6 millions solar masses. When the cloud collapses into stars, is it possible to know a rough figure for how much of this material actually ...
usernumber's user avatar
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Molecule formation when an atomic gas cools down

I have read about the actual formation of interstellar molecules; although interstellar chemistry is very different from solvent-based chemistry on earth, I understand it to be driven by the presence ...
SgtJohn74's user avatar
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Voyager 1 and 2 detected a 20-fold increase in plasma density, significantly different refractive index?

As reported by Nature.com, Voyager 1 and 2 detected a 20-fold increase in plasma density going from the heliosphere out to interstellar space. Does that 20-fold difference in density imply a ...
Gurnt's user avatar
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Cooling timescale for an interstellar dust grain

I would like to estimate the cooling timescale for an interstellar dust grain, starting at 200K, down to 100 K. The equation I have come up with is: $\displaystyle t_{cooling} = \frac{mC\Delta T}{Q_{...
lucas's user avatar
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What is the meaning of integrated emission maps for these chemical species?

In the Astrobites article Spectral Line Survey Reveals New Molecules in Two Protoplanetary Disks integrated emission maps depict the spatial distribution of the flux received from each "line.&...
LÜHECCHEgon's user avatar
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558 views

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 ...
kim holder's user avatar
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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 ...
RaRa's user avatar
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1 answer
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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 ...
revprez's user avatar
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Significantly blueshifted Lyman-$\alpha$

Lyman-$\alpha$ line in galaxies is notably known to show a double peaked profile, mainly due to its scattering in a moving medium, see e.g., the very recent Matthee et al. 2021, The X-SHOOTER Lyman-α ...
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4 votes
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Local Bubble in space

Is the Local Bubble alone in space or is there another bubble similar to the Local Bubble in space, i.e., do we live in a special place or is this a more general phenomenon?
ruan john's user avatar
4 votes
1 answer
194 views

Why do these astronomers say that "Carbon chains with more than nine atoms are unstable"?

The Phys.org article Interstellar iron isn't missing, it's just hiding in plain sight links to the paywalled article On the Structure, Magnetic Properties, and Infrared Spectra of Iron Pseudocarbynes ...
uhoh's user avatar
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4 votes
1 answer
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What is the specific heat capacity of interstellar clouds?

Star forming molecular clouds and especially Bok globules are low temperature $\sim 10 $ K environments with density on the order of $10^{-18}$ kg/m$^3$, mostly hydrogen with about 1% dust. What is ...
Anders Sandberg's user avatar
4 votes
1 answer
439 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
Rian's user avatar
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4 votes
1 answer
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Interaction of stellar winds in binary star systems

Binary star systems are fairly common but I am unable to find any information on how the stars interact with one another on aspects other than gravitational affects. Using Alpha Centauri as the ...
Markitect's user avatar
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4 votes
1 answer
902 views

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 ...
Mathias711's user avatar
4 votes
1 answer
52 views

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 ...
LocalFluff's user avatar
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4 votes
1 answer
187 views

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 ...
christopherlovell's user avatar
4 votes
1 answer
84 views

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 ...
user35915's user avatar
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3 votes
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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 ...
mivkov's user avatar
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1 answer
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What do these statements about interstellar magnetic fields really mean?

Quanta Magazine's The Hidden Magnetic Universe Begins to Come Into View is a fascinating review of a rapidly evolving field in astronomy. It contains some statements that I feel are important to ...
uhoh's user avatar
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3 votes
1 answer
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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 ...
quantumflash's user avatar
3 votes
2 answers
131 views

Are there examples of the effect of shock waves on chemical evolution in of interstellar medium or circumstellar medium?

Are there any examples of calculations or observations of suspected effects of shock waves on chemical evolution in interstellar medium or circumstellar medium?
user-2147482075's user avatar
3 votes
0 answers
149 views

Hydrogen Frost Line? Where, if anywhere, is it cold enough for Oort Cloud objects or rogue planets to have solid hydrogen on their surfaces?

I like the idea of Oort Cloud objects all being crusted with a thin layer of hydrogen snow, though what little information I've managed to find on the topic seems to imply that that is unlikely, ...
Mr. Nichan's user avatar
3 votes
0 answers
102 views

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 ...
RaRa's user avatar
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2 votes
1 answer
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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 ...
bandybabboon's user avatar
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