Questions tagged [hydrogen]
Questions about the simplest and most abundant element in the Universe.
57 questions
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How to use shift of H1 line to determine recessional velocity with 20m telescope?
I'm very new to astronomy, trying to find the recessional velocity of galaxies by finding how shifted the H1 line is. The galaxy I am using currently is NGC 7600, which is about 49 Mpc away and should ...
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How to calculate HI column density based on data cube
I have a data cube which has 3 axes: x(GLAT), y(GLON), v(VELO). Every pixel has value $T(x,y,v)$ in the unit of K.
I want to ...
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How rare are nebulae which emit H-Beta/H-Gamma/H-Delta? (Balmer series) [duplicate]
Most of the visible light emission nebulae have a lot H-alpha emissions, and because of that appear red.
But why are other Balmer emissions much rarer? Do they need a hotter environment which is ...
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Star forming regions
Some star forming regions, like Bok globules (which contain stars that still haven't dispersed their molecular hydrogen and cosmic dust shell) appear dark compared to the rest of the H II in which ...
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Is there any way to detect the three-dimensional distribution of baryonic gas in our Universe?
As the title suggests, can the current observational techniques detect the 3D large-scale distribution of the baryonic gas, rather than just the gas within groups or clusters?
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How are we observing the newly discovered "dark galaxy" J0613+52, if it has no stars and is so far away from other galaxies?
I just came across a New York Times article talking about a newly found Low Surface Brightness (LSB) galaxy (also called “ultra-diffuse galaxies” or “dark galaxies”). The new galaxy, J0613+52, was ...
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Radius of hydrogen cloud
I am using a 1.4 meter parabolic dish with HPBW of 10 degrees and a RTLSDR to study our milky way in hydrogen line. The structure of the galaxy is deduced as shown in the picture by plugging the ...
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How much of the hydrogen in our sun will never participate in fusion? What about larger stars? [duplicate]
From what I gather, only red dwarf stars are fully convective, and will use up pretty much all of their hydrogen....
Is there a chart or list somewhere that shows the percentage of hydrogen that is ...
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Are red giants still primarily made of hydrogen? What is their exact composition?
How much lower is the ratio of hydrogen to helium in a red giant vs a 'normal' main sequence star like our Sun?
Also, how low does the ratio get at the end of a red giant's life? (Just before it ...
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What accounts for a Lyman-break for all wavelengths shorter than 91.2nm if the Lyman limit is the highest energy photon that neutral hydrogen absorbs?
From this description of Lyman-break galaxies, I don't understand how:
...radiation at higher energies than the Lyman limit at 912 Å is almost completely absorbed by neutral gas around star-forming ...
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Does the existence of hydrogen in the universe create an obscuration effect similar to the way air does at great distances?
I've had this question for a while. I understand the universe is full of "dust". I am also aware of the fact that there is an average measure of particle density in the universe.
I am ...
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What is the elemental composition of the Sun overall, rather than at the photosphere?
Many sources claim that the Sun is around $70-74\%$ hydrogen and $25-27\%$ helium by mass, or $91\%$ and $9\%$ by atom count, without any further caveats - e.g. 1, 2, 3. I believe these sources are ...
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The Relationship between Surface Temperature and Mass of MS and Red Giant
The assumptions about the problem situation are as follows :
The red giant is in the HB at HR disgram, and it's a helium fusion situation. And in this situation, the mass of the red giant is the ...
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Using Saha's equation knowing the overall pressure
Knowing the pressure, $P_g$, how can I calculate $\frac{N_{I+1}}{N_I}$ using Saha's equation?
If I assume that $P_g=(n_e+n_{H^+}+n_H)K_B T$ and that $n_e=n_{H^+}$, I can find the electronic pressure, $...
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Is it possible for stars to not begin fusing hydrogen at all?
As far as I know, stars (virtually all stars) begin fusing hydrogen into helium, and the rest happens based on the mass and luminosity and etc.
Out of curiosity, I was wondering: is it even possible ...
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Is it possible to observe Lyman-continuum emission from extragalactic objects?
Lyman-continuum (LyC) emission is everything blueward of 912 Angstroms (so it includes extreme UV photons, X-rays and gamma rays). There are many low-redshift astrophysical plasmas such as the diffuse ...
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What is the significance of the velocity resolution in spectral line observations using radio interferometry?
I've always struggled to conceptualize the term "velocity resolution" in spectral observations. In principle, it is simple to calculate. For example, one can take the spectral width 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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How many generations of stars can be formed in the Stelliferous Era?
As in general case, stars are formed from nebula which in some case itself is the result of a supernova.
Also stars need hydrogen to become a star (to do nuclear fusion), but stars consume hydrogen in ...
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Where did the hydrogen come from in a type II supernova?
Type II supernovae have hydrogen. Where did the hydrogen come from if that is the first element used up in the star's life cycle? Also if our solar system was seeded from an ancient supernova where ...
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How small could an orbital system be in our solar system?
Answers to How does the Sun's gravity have so much force and pull on the solar system? How does it scale? Newton's law of gravity scales on orbits so that we can theorize very small orbits with very ...
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How to convert between spectra given in terms of velocity (km/s) to wavelength spectra?
I have H alpha spectra of H II regions in our galaxy. In the paper, the x-axis is in units of km/s and the corresponding line width as well. From this, how can I get equivalent width of the H alpha ...
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How to isolate H$_\alpha$ from Nitrogen doublet emission lines
I am trying to find out line intensity and FWHM of H$_\alpha$6565 emission line from a quasar spectrum obtained from SDSS DR-14Q. Visual inspection of spectrum shows H$_\alpha$ being contaminated with ...
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Would stars have formed in the Universe if atomic hydrogen couldn't make molecular hydrogen?
I just saw this YouTube video made by PBS Studios. There they explain that $H_2$ can reduce the traslational kinetic energy of regular $H$ atoms when it is formed since the energy can also be stored ...
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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 ...
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Is most hydrogen in the universe in the form of plasma, atomic neutral hydrogen, ionized hydrogen, or molecular?
I have had trouble finding an answer somewhere....
Some places say most hydrogen is plasma, such as the stuff stars are made of (mostly) and the 'warm-hot intergalactic plasma'.
Other places say ...
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Can a high enough density ignite a gas giant into a brown dwarf?
I wonder whether the nuclear fusion of brown dwarfs and more massive stars really depends on their mass only or if it could also start nuclear fusion if it is dense enough but not as massive as brown ...
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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, ...
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Is Jupiter a failed star?
The elemental make-up of Jupiter is about entirely hydrogen and helium, along with a very small fraction of the atmosphere being made up of compounds such as ammonia, sulfur, methane, and water vapor. ...
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Replenishing hydrogen in the core of the sun
How is hydrogen supplied to the core of the sun? Shouldn't the radiative zone prevent this? Shouldn't heavier helium fill the core? How much of the hydrogen can the sun fuse?
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Is there any possibility that a gas planet turns into a star [duplicate]
Since the sun is made of one of elements hydrogen
Why Saturn and jupiter doesnt turn into a star since they have a elements of hydrogen ?
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Tuning radio telescopes
In a paper called Further Observational Evidence for a Critical Ionising Luminosityin Active Galaxies, Section 2.1, the authors talk about using the ICRF2 to find a tuning frequency in search of the ...
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If the Higgs field only formed after the Big Bang, how was hydrogen formed?
These two statements seem to conflict, but since we're here they can't:
Electrically charged particles cannot be massless.
Hydrogen was created at the moment of the Big Bang.
However, the Higgs ...
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Where did the Sun get hydrogen to work with if it is in the 3rd generation of stars?
As I see here, the Sun belongs to the Population I group of stars, which is the 3rd generation of the stars in our universe. 1st generation stars are Population III, 2nd generation are Population II, ...
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Hydrogen Line observation - Interference from trees
I am setting up a 2.4 metre parabola pointing straight up to observe the 21cm hydrogen line at 1420MHz with meridian drift scans.
I'm planning to place the dish on a steel pole embedded in the ...
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What fraction of a star's hydrogen store will be fused over its lifespan?
A main sequence star will fuse some of its hydrogen, but not all. In massive stars ($>1.5M_\odot$) the core is convective but the rest of the atmosphere radiative and hence does not mix much: as it ...
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Helium rain inside metallic hydrogen within Jupiter, conditions and experiments?
In response to today being pi day (also see http://www.piday.org/), NASA has published it's fifth annual pi in the sky day 5 activity set (see also NASA goes the distance and Celebrate Pi Day with ...
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Can I slice off a piece of the Sun?
Bear with me. I want to explain this to my 6 and half year old.
If, all things being equal, we could reach out to the Sun with a suitable implement, a gigantic space knife, could we cut a piece off ...
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Relation between molecular cloud mass and galactic mass
Would it be true to assume that the mass of a galaxy is approximately the mass of all molecular clouds detected within it, let's say, through CO observations and then converted to H$_2$?
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Hydrogen and oxygen in space
chemistry tells us that when mixing hydrogen and oxygen the result is an explosion and water.
my question is: does this happen on astronomical scale? for example, did they ever observe planet-size ...
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What percentage of the hydrogen today has never been in a star
It stands to reason that some of the hydrogen and helium that formed directly as a product of the big bang might never have fallen into a star to re-ejected when that star explodes. My question is, ...
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Are all gas planets guaranteed to produce their own magnetic field?
All gas giants in the solar systems have two things in common: abundant hydrogen gas and a magnetic field.
I'm wondering: could there be a gas planet that somehow can't produce any magnetic field on ...
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Why does lithium fuse at lower temperatures than hydrogen?
This is a basic question, but it's been bugging me. In the Wikipedia article for lithium burning, it states that:
Stars, which by definition must achieve the high temperature (2.5 × 10^6 K) ...
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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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If there are neutron stars, would most stars be considered "proton stars"?
For example, the Sun is a giant sphere of positively charged plasma. About 72% of the elements in it are protium. This means that these protium atoms would have had to lose their electrons, right? If ...
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Why does hydrogen ionization happen in HII regions?
Why does hydrogen ionization happen in HII regions? Why is the hydrogen there ionized?
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Are hot stars like O-type stars entirely composed of helium?
Hot stars like O-type stars show no hydrogen in their spectra. Does this mean they are made entirely of helium?
Any explanation would be really helpful.
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What are the implications if the Sun was formed in a warm nebula?
Molecular oxygen O2 has been found on comet 67P/C-G in a ratio of 3.8% to water, which is much higher than expected. An explanation proposed is that the Solar System formed from a molecular cloud ...
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Could evaporating hot Jupiters have metallic hydrogen on their surfaces?
Jupiter is believed to have metallic hydrogen in its core. And gas giants that migrate to become hot Jupiters are believed to evaporate, have their atmospheres blown away by their nearby star. Can ...
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Why are there no green stars?
There are red stars, and orange stars, and yellow stars, and blue stars, and they are all understandable save the fact that there is a 'gap': There are no green stars.
Is this because of hydrogen's ...
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