Questions tagged [helium]

Second lightest element in the periodic table

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25
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2answers
10k views

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. ...
7
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1answer
578 views

What is the most appropriate way to estimate the helium composition of a star?

Say we have to estimate the helium content in Proxima Centauri. We begin by calculating the content of helium in the Sun (source): $24.85$% of $2.10^{30}$ kg. Mostly all the energy is generated due ...
4
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2answers
187 views

Where can I find Helium 3 in our solar system?

What are the best locations within the solar system to find Helium 3 excluding the Sun? Where is Helium 3 most abundant after the Sun?
4
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1answer
139 views

How much helium has been created since the Big Bang?

When I try to find figures for the amount of helium today and just after the Big Bang, I get similar figures. I was expecting that all of the stars since then would have created more helium. Is the ...
9
votes
1answer
158 views

What percentage of Helium-3 is primordial vs produced in stars

I tried to research but what I found is pretty limited. A very tiny but non zero percentage of primordial matter was Helium-3 or 3He. Stars produce 3He as part of the proton-proton chain but they ...
3
votes
1answer
210 views

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 ...
6
votes
3answers
298 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 ...
5
votes
1answer
136 views

Why Helium could be produced in first minutes of big bang but not heavier elements

At what extent could be sure that no heavier elements than helium could be produced, if we know that matter in universe today is about 25% composed on helium, why could be so sure that the kind of ...
2
votes
1answer
101 views

Ionization Fraction of Helium in alternate, He dominated early universe

I'm asked to verify an expression for the ionization fraction of helium in a universe in which helium dominates baryonic matter. I'm given that the ionization fraction $X = \frac{n_{He^+}}{n_{He^+}+...
1
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2answers
277 views

Fate of helium moving toward a singularity

On the molecular level, if an atom, consider helium, were to fall into a black hole, what would be the ultimate fate of its electrons, protons and neutrons?
4
votes
1answer
373 views

Is there a single, most prominent helium line?

There's a prominent spectral line at ~1420 MHz caused by hydrogen. From what I can tell, this is the most notable electromagnetic emission from hydrogen in radio astronomy. Is there an equivalent ...
1
vote
1answer
176 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.
2
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2answers
1k 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] ...
2
votes
1answer
142 views

What came first: the Sun shining or the existence of helium?

This seems to be a chicken and egg problem, the sun begins shining due to hydrogen becoming helium, but it's odd that there was no helium initially without the stars. Is my logic flawed? (Note: ...
5
votes
3answers
632 views

At what density does helium burning start in a star?

I have seen several references that say that helium burning begins in a star once the core temperature reaches $10^8$K (such as here) but nowhere that says what density that corresponds to. Does ...
2
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1answer
456 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\...