# Tag Info

86

Yes. It does not rotate uniformly though, different portions have a different angular velocity (as a body made of plasma, it can get away with this). Measuring this in theory is pretty easy, we just need to track the motion of the sunspots. This isn't as simple as calculating the changes in relative positions of the sunspots, though, as the Earth is ...

63

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 $\sigma T^4$, where $\sigma$ is Stefan's constant. Even at any particular wavelength it is always the case that a blackbody of higher temperature is brighter than a ...

34

Yes, the Sun rotates. This can be observed by tracking a variety of features on the Sun, such as sunspots, X-ray brightpoints, coronal holes, filaments, and small magnetic flux elements. Another way to determine the rotational speed of the Sun is to measure spectral lines at the edge of the Sun's disk and determine their redshift. It is thought that the ...

15

Although its too late to reply to this interesting question but trying to add few more points. Yes the sun rotates. Now the question arises as to how we can check that? We can observe this by observing sunspots. All sunspots move across the face of the Sun. This motion is part of the general rotation of the Sun on its axis. Observations also indicate that ...

15

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 dark. However, it is opaque to virtually all light outside the sun. To provide an analogy, if you are in a sealed room with no windows, you cannot see anything ...

11

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 energy transitions around 425 nm (4250 Angstroms), which is in the blue part of the visible spectrum: Spectrum of Comet C/2016 R2 (Pan-STARRS), Figure 2 from ...

9

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 place-to-place. It is hottest ($\sim 10^{7}$ K) in magneticloops undergoing flares, which tend to be anchored in low latitude regions. It is coolest (a bit less ...

7

Yes, Sun has differential rotation. Movement of Sun spots is one of the proofs that Sun rotates. The differential rotation causes the weird twisted magnetic fields which shows in the Sun's prominence.

7

I can tell you just from this page alone that it's a bunch of pseudoscience and quackery. These folks are conspiracy theorists and catastrophists. Please correct me if there is, but I cannot find a single article on this that is published in a reputable, peer-reviewed journal.

5

Silicates are rather stable, and there are only small amounts of protons in the interplanetary space near a comet, hence only tiny amounts of hydroxyl or water can form within a short period of time by photochemical processes. Thus the hypotheses of the Thunderbolt Project can easily be discarded. The surface of comets and asteroids will be charged by ...

5

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 photon and conserve energy and momentum) in a plasma at low photon energies. That is basically due to their much lower masses (classically you can think of the ...

4

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$^{-1}$. The inverse of this is the optical depth. You can see stuff through about 2-3 optical depths, so your "horizon", looking horizontally in the solar ...

4

I have not the qualification to answer the question in its whole but the question is interesting (I worked on Be Stars which are episodically surrounded by an decretion disk and which rotates at nearly critical velocities. The phenomenon in Be stars is different from accreting stars. The only consequences of subcritical velocity is a flattened envelope and ...

4

Yes the sun rotates and it takes about 26.24 days.They are many methods to determine the rotation periods but most common one is by observing sunspots. Here's a link with a detailed explanation https://en.wikipedia.org/wiki/Solar_rotation.

4

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 Sun rotates, in a way consistent with the change in perspective looking onto a slightly depressed region. While this isn't the only explanation for the effect, ...

3

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 case is believed to be correct, and it pretty well described in Wikipedia. I'll summarize. Immediately after the Big Bang (10-20 seconds or so) the universe was ...

2

The analogy is rather weak and not really useful. So-called collisionless stellar systems (those for which relaxation by stellar encounters has no appreciable effect over their lifetime), such as galaxies, can be described by the collisionless Boltzman equation, but never settle into thermodynamic equilibrium (only into some dynamical or virial equilibrium)....

2

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 travelling at these speeds you don't have a river, more a beam, or a jet or particles. These are produced by active accretion disks around black holes. In ...

2

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 describe waves in the frequency band ~3 Hz to ~3 kHz. Very low frequency (VLF) is used to describe waves in the frequency band ~3 kHz to ~30 kHz. Generally the ...

2

Magnetic fields are generated by currents - i.e. by the motion of charged particles. As you say, the Sun is full of freely moving charged particles, and these generate currents which in turn generate magnetic fields. No metals required. Most of the magnetic field generation is thought to occur at the interface between the radiative interior of the Sun and ...

2

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 North or the South. Two magnets will attract or each other because the North pole of one is nearer the South pole of the other. You can get a net force on a ...

1

The index of refraction of a plasma is the square root of the permittivity: $$n=\sqrt{\epsilon}=\sqrt{1-\frac{\omega_p^2}{\omega^2}},\quad \omega_p\equiv\left(\frac{n_ee^2}{\epsilon_0 m_e}\right)^{\frac{1}{2}}$$ where $n_e$ is the electron number density and $e$ is the elementary charge. Note that $n$ is frequency-dependent, and so the difference in ...

1

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 akin to dust particles leaving a comet-- their path is more affected by light pressure than magnetic pressure, but for a large object, neither of those could ...

1

If you were place a strong permanent magnet into the solar wind, like a 1 inch cube neodymium magnet, would the charged particles of the solar wind colliding with the magnet's magnetic field push the magnet out of our solar system ... Technically speaking, yes. Practically speaking, it would take an extremely long time. The solar wind consists of 5 atoms ...

1

There just aren't any other mechanisms to keep the population excited in a Stromgren sphere. In principle collisions can also lead to excitations, but if you do an order of magnitude calculation you'll find that the time between collisions is much longer than the time to receive an ionizing photon. In a laboratory setting you might be able to coerce some ...

1

There is an interesting paper by Jes Madsen, which has some success modelling globular clusters as isothermal spheres.

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