Questions tagged [disk]

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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
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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
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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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