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76 votes
Accepted

Is it dark inside the Sun?

No, it's not. The radiation field in the interior of the Sun is very close to a blackbody spectrum. If you look in any particular direction the brightness (power per unit area) you see is $\sigma T^4$,...
ProfRob's user avatar
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51 votes
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Is the Solar core hard?

The solar core can be considered soft in a relative sense (compared to other materials at the same density), but hard and incompressible in an absolute sense. The material behaves almost exactly like ...
ProfRob's user avatar
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18 votes

Is it dark inside the Sun?

Coming from a different direction as @Rob's, Opacity and Thermal Radiation are orthogonal properties of a material. The photon flux at the interior of the sun is very high, so it is definitely not ...
MooseBoys's user avatar
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15 votes

Is the Solar core hard?

If one thinks about "hard" as solid, having stiffness/rigidity, an ability to retain a certain shape when subjected to anisotropic stress, then the answer is NO, it is not hard. The solid ...
fraxinus's user avatar
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12 votes
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Blue color of ion (plasma) comet tails

Close, but not quite right - the blue light is indeed emission from CO$^+$, but it's from the CO$^+$ ions themselves, with no need for recombination to CO; that (ionized) molecule has a strong set of ...
Eric Jensen's user avatar
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10 votes
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What is the temperature of the solar atmosphere (the corona) and how is it measured?

This is a rather broad question and this will not be a fully comprehensive answer. There is no single temperature to the solar corona. The coronal temperature varies by an order of magnitude from ...
ProfRob's user avatar
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10 votes

Is the Solar core hard?

It is not solid. But it is hard. Its Young's modulus is about $10^{16.5}\text{ Pa}$. It is thousands or millions of times more than the Young's modulus of any ordinary solid matter. For comparison, ...
Imyaf's user avatar
  • 301
7 votes

Density of Plasma in Solar Corona

It depends on which region you consider. The lower corona has a plasma number density of the order of $10^9 cm^{-3}$, the upper corona about $10^5 cm^{-3}$. This is all quite variable though, ...
Thomas's user avatar
  • 3,504
6 votes

Do free protons and neutrons absorb much radiation? To affect astronomers' observations? If so, at what wavelength(s)?

You cannot have free protons without electrons. Plasmas, in general, are electrically neutral. It is usually electrons that dominate the scattering (note that a point-like charge cannot absorb a ...
ProfRob's user avatar
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5 votes

Do the newly-created deuterons in our Sun release any photons? In addition to a positron and an electron neutrino?

Does the newly-formed deuteron then automatically release a photon? Not directly. The initial step of the p-p chain is a weak interaction rather than an electromagnetic interaction. This initial step ...
David Hammen's user avatar
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4 votes
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Just after the Big Bang, was the space, in its entirety, filled with Hot gas?

I'm not sure what you mean by "nebulae". You could mean "matter in a gaseous or plasma state" or "cloud of low density gas and dust in space" (which is what astronomers mean by nebulae.) The former ...
Mark Olson's user avatar
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4 votes
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How far can you see in solar plasma at just under 1 solar radius?

If you have a look at the top-left panel of Fig.11 in these lecture notes by Rob Rutten, you will see that the continuum opacity at optical wavelengths at the photosphere is about $10^{-6.7}$ cm$^{-1}$...
ProfRob's user avatar
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4 votes
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Will the Sun's solar wind push a permanent magnet out of our solar system?

No. The magnetic field has two poles, the force on the two pole of the magnet is equal and opposite. This is why a compass needle will align in the North South direction, but is not pulled towards the ...
James K's user avatar
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4 votes
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Are sunspots vertically displaced from the surrounding photospheric plasma?

Yes. The idea that sunspots are depressed slightly came as a possible explanation for the Wilson effect. The Wilson effect was discovered as the shape of sunspots as viewed from Earth changed as the ...
HDE 226868's user avatar
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4 votes
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Would impacting plasma clouds destroy electronics on Earth or make them only temporarily inactive?

tl;dr: The electronics that depends on the power grid, or GPS or communications satellites signals will be indirectly affected, and older electronics plugged into the power grid might be overloaded/...
uhoh's user avatar
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3 votes

Do the newly-created deuterons in our Sun release any photons? In addition to a positron and an electron neutrino?

No, deuteron production doesn't directly release a photon. Of course, when the positron annihilates with a nearby electron, that creates some gamma photons. As David Hammen mentions, the proton-...
PM 2Ring's user avatar
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3 votes
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Numerical Programming using ODEINT takes more than 17 minutes

My first recommendation is to drastically increase the step size. Both odeint and solve_ivp use adaptive integrators. Keep in ...
David Hammen's user avatar
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3 votes

Is the Solar core hard?

The Sun's core is mind-bogglingly dense, about 150,000 kg/m3 (about 15x denser than lead, 7x denser than uranium, 6x denser than osmium). Such a high pressure would compress matter into a wigner ...
Kevin Kostlan's user avatar
2 votes

Do some ELF (Extremely low frequency) radio waves pass the atmosphere

Do some ELF (Extremely low frequency) radio waves pass the atmosphere reach Earth surface and then are reflected passing the atmosphere again to reach outer space? In space plasmas, ELF is used to ...
honeste_vivere's user avatar
2 votes

How to determine arrival time delay given dispersion measure?

As is the case with light traveling through any medium, radio waves traveling through space experience refraction, which reduces their speed. A wave of infinite frequency will experience no refraction,...
HDE 226868's user avatar
  • 37.2k
2 votes

If interstellar medium was dense plasma and light slowed down, would things appear to move slower far away?

If light moved slower in this dense plasma, would it appear like events in other solar systems played out slower than they actually do? First, the interstellar medium is not a "dense" ...
honeste_vivere's user avatar
2 votes

Could there be massive charged “rivers” in interstellar space?

Define "current". If one particle makes a current, there are lots of particles that hit the Earth at energies much more than 0.98c, most famously the "Oh my god particle" If you have many particles ...
James K's user avatar
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2 votes

Is the Solar core hard?

Solid is one of the four states of matter which is uncompressible with atoms that are bound together. The sun's core is compressible and its atoms are completely unbound. Apply a bit of extra force or ...
bandybabboon's user avatar
  • 4,268
2 votes
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Is it possible to observe Lyman-continuum emission from extragalactic objects?

I think the short answer is "You can't observe $z=0$ LyC leakers, but you can observe $z\sim0$ LyC leakers." No z = 0 leakers… Measuring the Lyman continuum (LyC) — i.e. photons capable of ...
pela's user avatar
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1 vote

How is the H II 'region' directly detectable? By Compton or Thomson free-particle scattering? At what wavelengths?

HII regions or emission nebulae are associated with the presence of massive stars that ionize the gas. The strongest emission line from an HII region comes from H-alpha. What happens in this case is ...
Astroturf's user avatar
  • 1,111
1 vote

Is **Voyager I’s** reduced data transmission rate as described in [this article][1] because of the distance or because its transmitter getting slower?

Transmitters don't slow down as they age. Red shift isn't involved, at all. As a transmitter gets further away the signal at the receiver gets weaker, so it's deliberately slowed down. Data channel ...
stretch's user avatar
  • 1,797
1 vote

Voyager 1 and 2 detected a 20-fold increase in plasma density, significantly different refractive index?

The index of refraction of a plasma is the square root of the permittivity: $$n=\sqrt{\epsilon}=\sqrt{1-\frac{\omega_p^2}{\omega^2}},\quad \omega_p\equiv\left(\frac{n_ee^2}{\epsilon_0 m_e}\right)^{\...
HDE 226868's user avatar
  • 37.2k
1 vote

Will the Sun's solar wind push a permanent magnet out of our solar system?

The Sun's gravity would pull in any large object not already in orbit, that would be dominant over magnetic forces from the very weak wind. If the object was already in orbit, the situation would be ...
Ken G's user avatar
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