Questions tagged [interstellar-medium]
Questions about the gas that lays between stars in galaxies.
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How to count observable number of galaxies at a given latitude considering interstellar extinction?
If galaxies are uniformly distributed in space, then in the absence of extinction, the number of galaxies per square degree brighter than magnitude m is given by $$\log_{N_0}(m) = 0.6m + C$$
How will ...
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Electron Temperature of a Gas Cloud
Would a gas cloud made of HII and OIII have a higher electron temperature than a cloud just consisting of HII? I understand that electron temperature is the temperature of the electrons in a plasma, ...
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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 ...
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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_{...
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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-...
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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 ...
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What are the differences between Intergalactic Medium, Interstellar medium and Intracluster medium?
The Intergalactic Medium, Interstellar medium (ISM) and Intracluster medium (ICM) are mediums that fills the space between galaxies/pace between the star systems in a galaxy. What are the differences ...
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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.&...
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Largest projected images (such as shadows) observed
Serpens Nebula around the star HBC 672 (source: heic1819b)
Which are the largest observed images projected onto interstellar bodies (such as nebulae) by means of electromagnetic radiation? By “largest”...
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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 ...
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What does it mean for cold clouds to be in pressure equilibrium with a diffuse hot medium?
I often read about cold objects (namely cold clouds in the Galactic halo or cold filaments accreting into high-redshift galaxies) being in pressure equilibrium with the diffuse hot ambient gas. What ...
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Why space-based VLBI scattering sub-structure is "Hopefully, a new promising tool to reconstruct the true image of observed background target(s)"?
@HDE226868 mentioned in the observatory that the GBT@20 – The Celebration; Twenty Years of Innovation and Discovery was going on. There are plenty of YouTube videos and slide sets available as links. ...
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Why does rotation prevent the further contraction of the cloud?
In the book Horizons: Exploring the Universe (2018) by M.Seeds and D.Backman, chapter 9, page 170-171, it states that:
At least four factors resist the
compression of an interstellar gas cloud, and ...
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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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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 ...
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