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Questions tagged [disk]

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Why is the lunar disk completely black during solar eclipses?

I noticed that during solar eclipses the lunar disk looks completely black, it is impossible to see any relief details on it. At other times, the unlit part of the Moon is quite clearly visible. An ...
Vladimir Orlov's user avatar
4 votes
0 answers

Total scattered flux and polarization for a ring of dust particles close to a star

I have an important problem and maybe some of you can help me with the following question: I have a mathematical expression for the total scattered flux in Jansky and the total linear polarized flux (...
Lyapunov's user avatar
6 votes
1 answer

Why did supernova 1987A's "String of 'Cosmic Pearls'" appear to be so lumpy 20 years later? Is it still?

NASA's A String of 'Cosmic Pearls' surrounds an exploding star is beautiful and the page says: This image shows the entire region around the supernova. The most prominent feature in the image is a ...
uhoh's user avatar
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1 vote
1 answer

How to approximate the distance at which the thin disk peaks along a given LOS from Earth for a given galactic coordinate per 1 sq deg?

The density of stars drops off exponentially from the center of the galaxy and can be approximated as follows using a cylindrical coordinate system: $$ \rho(R, z) = \rho_0 \exp \frac{-R}{h_R} \ \exp \...
Astroturf's user avatar
  • 1,111
5 votes
1 answer

Are warm circumstellar debris disks still able to be detected at sub-millimeter wavelengths?

At these wavelengths a survey is more sensitive to detecting relatively cool disks (T<100k), but would a telescope operating in the sub-millimeter be less sensitive to warm debris disk than say, a ...
Joshua's user avatar
  • 53
6 votes
3 answers

Why isn't the black hole white?

I recently saw the first image of a black hole. As I understood, it is covered with bright, hot matter. In this case, how can we see the black disk (event horizon), instead of a bright disk due to the ...
Cristian M's user avatar
2 votes
0 answers

Need help on Springel model for galaxy simulation

I am working on a code for galactic dynamics simulation. Initial conditions (positions and velocities) are based on a model with a massive dark halo and a thin exponential disk. Now, from the ...
user avatar
3 votes
2 answers

Difference between "planetary ring" and "circumstellar disk"?

Related: Do/Can Ringed Stars Exist? Is there any particular difference, in behavior or properties, between a planetary ring system and a circumstellar disk? Or is the only real difference a matter of ...
Iszi's user avatar
  • 203
2 votes
1 answer

How is the maximum density in a circumstellar disk determined?

I'm working with some equations to model the evolution of a circumstellar disk. One of the equations is $$\rho(r)=Ce^{-\frac{(r-r_{peak})^2}{2 \sigma ^2}}$$ where $\rho$ is density, $r$ is the ...
HDE 226868's user avatar
  • 36.6k
5 votes
1 answer

Number density of stars on the Galactic plane

The number density of stars (e.g. the number of stars per cubic parsec) is given by $$N(z) = N(0) e^{-|z|/h}$$ where $z$ is the height above the Galactic plane, $h$ is the scale height for a specific ...
Dieudonné's user avatar
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