Unanswered Questions
206 questions with no upvoted or accepted answers
10
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0
answers
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How well conserved is etendue in extreme gravitational lensing scenarios?
This excellent answer to Could dark matter exist in the Universe in the form of sufficiently dense objects? includes the following image and description:
Light from the background galaxy circles a ...
- 30.7k
8
votes
1
answer
622
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Why do the Sun and gas planets rotate faster at equator than at poles?
From this site, it states that:
The Sun spins faster at its equator than at its poles.
I have also read somewhere that the gas giants (gaseous planets like Jupiter, Saturn, Uranus, and Neptune) also ...
7
votes
0
answers
256
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Get the expression of probed volume between 2 redshifts
1) I can't manage to find/justify the relation (1) below, from the common relation (2) of a volume.
2) It seems the variable r is actually the comoving distance and not comoving coordinates (with ...
CommunityBot
- 1
6
votes
0
answers
482
views
Linear limb darkening coefficient, u
I was wondering if anyone knew of any resources to understand the linear limb darkening coefficient, $u$. That is to say, how the $\theta$-dependent coefficient $u$ (or sometimes $b_{\nu}$) varies ...
- 1,374
5
votes
0
answers
70
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Do all the accretion disks around a compact object (black hole or neutron star) emit astrophysical jet outflow?
Do all the accretion disks around a compact object (black hole or neutron star) emit astrophysical jet outflow? I mean is it mandatory for a jet to be emitted from an accretion disk?
If so, then why?
...
- 2,169
5
votes
0
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128
views
Explain as simply as possible how the Sunyaev-Zeldovich (SZ) effect is used to estimate the Hubble constant
The Sunyaev–Zeldovich effect (SZ effect) is useful in determining the Hubble constant because it is independent of the cosmic distance ladder. This effect occurs when CMB (cosmic microwave background) ...
- 30.7k
5
votes
0
answers
37
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Help understanding ring diagram analysis used in helioseismology
I need help understanding something. In global helioseismology we study the modes directly (stationary waves characterized by 3 integers numbers: $n$, $l$ and $m$). As the angular degree $l$ becomes ...
- 30.7k
5
votes
0
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186
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What are some good books/online resources for astronomy problem sets?
I am currently studying for the international olympiad for astronomy and astrophysics (the syllabus can be found here: https://www.ioaastrophysics.org/syllabus/). I am currently using Carroll Ostlie's ...
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5
votes
0
answers
100
views
Simulate earth, moon, sun constellation with dates
I would like to simulate the three object distance, specifically the distance of the moon to both, sun and earth for further investigation into tide prediction.
What would be a good starting point ...
- 151
5
votes
0
answers
62
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Strength of core-envelope coupling in stars
For a star with a given Zero-Age Main Sequence (ZAMS) mass, as a function of metallicity how strongly is the star's core coupled to its envelope?
I understand that the core-envelope boundary is only (...
- 4,533
4
votes
0
answers
124
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CMBR: Is the cold spot a hint at the edge of the universe?
Could the big cold spot in the CMBR map be a sign that almost all radiation from that direction has already passed us, and that be a sign that the end of the universe is closest to earth in that ...
- 30.7k
4
votes
0
answers
60
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Explanation for Planck 2018 temperature fluctuations strongest peaks
As it can be seen from Plank 2018 Cosmic Microwave Background temperature fluctuations data-
There are 3 sharp peaks at multipole expansions $\ell \approx 250, 550, 800 $. Also as multipole expansion ...
4
votes
0
answers
60
views
How are plage regions related to the density of medium and velocity FeII ions?
During a literature review (abstract), I found that the intensity of FeII (298.5 nm) ions in the last solar minimum was higher than the two previous solar minima 21 & 22. The velocity of FeII ions ...
- 30.7k
4
votes
0
answers
72
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Did astronomers "track back" solar wind switchbacks to the surface of the Sun to individual convection cells?
The new NASA Goddard video NASA's Parker Solar Probe Touches The Sun For The First Time explains that the spacecraft passed many times through "switchbacks" or kinks in the solar wind, where ...
- 30.7k
4
votes
0
answers
113
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How much more mass would Mars need to currently have enough pressure for liquid water and oxygen?
My question is whether Mars just about failed to meet the threshold or missed it by a lot. It's been dry for 3 billion years. How much bigger would it have needed to be to buy it that extra time? Let'...
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