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Questions tagged [hydrogen]

Questions about the simplest and most abundant element in the Universe.

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What's wavelength of the hydrogen atom determines the speed of the gas orbiting at the outer edge of the Milky Way?

The 21-cm spectral line emitted by the hydrogen atom is used to study the structure of the Milky Way because the wavelength is too long to be blocked by the dust in interstellar space. What ...
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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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3answers
209 views

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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381 views

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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1answer
144 views

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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1answer
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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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1answer
201 views

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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1answer
143 views

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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1answer
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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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563 views

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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1answer
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Is the sun too small to self-ignite?

I recently heard in a discussion that the sun is not massive enough to self-ignite via core-pressure. It simply has not enough mass to "generate" the gravitational force needed for that. The reason ...
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2answers
671 views

What is the minimum size of a ball of gas to become a star?

I know there are two criteria to meet in order for nuclear fusion to occurs. High temperature (many times temperature at Sun's core) High pressure (protons are very close to each other) [Goal] ...
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1answer
310 views

How are stellar elemental abundances quoted?

Close to the bottom of page 4 of this article (marked as page 164 in the upper left corner) states Values are given in the logarithmic scale usually adopted by astronomers, A$_{e\ell}$ = log N$_{e\...
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Is there enough hydrogen left after a star dies so another star will have enough to light up?

A star consumes quite a lot of hydrogen in its life, and is pretty much "vacuuming" everything in its vicinity. After it dies (eventually by supernova which will spread all its composition over light ...
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1answer
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In the end what is the ultimate matter/element in the universe, due to fusion process in stars?

We know that, in stars, hydrogen is used by the stars and due to the fusion in two hydrogen elements we get helium -> Carbon -> Oxygen ->Other elements -> Iron -> then Super/Hypernova. If everywhere ...
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Density of hydrogen between galaxies

From watching a video on youtube, it states that Dark Matter is 6 times more abundant than known matter. I was wondering if it was possible to have hydrogen clouds between the universes galaxies. The ...
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Could dark matter particles be unstable?

Is it possible that dark matter particles are unstable and the existing dark matter will decay in the long run and turn into hydrogen, for example? What would be possible mechanisms for such a decay? ...