Unanswered Questions
246 questions with no upvoted or accepted answers
10
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0
answers
214
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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 ...
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 ...
6
votes
0
answers
105
views
What's the number density of `Oumuamua like objects?
Recently, the fly-through the Solar system of the inter-stellar object (ISO) `Oumuamua caused quite a stir in the astronomy community. I wonder whether there are reliable estimates for the (local) ...
6
votes
0
answers
69
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What is the reason for the dispute over the variation of core mass with heavy metal abundance?
In Metal-Poor Stars IV: The Evolution of Red Giants, Rood writes
The differences in the results of these papers are large enough to introduce appreciable uncertainties into the study of the ...
6
votes
1
answer
189
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Do narrow lines in the spectra of O- and B- type stars always indicate magnetic fields?
I was reading a paper on the differential emission measures of a set of hot O- and B- type stars. As the authors discuss in Section 3 (page 959), two stars, $\tau$ Sco and $\theta^1$ Ori C, have ...
6
votes
1
answer
510
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Could non-supernova carbon, oxygen, or silicon flashes be observed?
I was reading about the helium flash, the short but sudden onset of helium fusion in certain red giant stars. As I understand, the upper (nondegenerate) layers of the star absorb the energy as they ...
5
votes
0
answers
70
views
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?
...
5
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0
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100
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How do the giant planets excite the orbits of asteroids?
The giant planets, particularly Jupiter, are notorious for bringing about changes in eccentricities and inclinations of smaller bodies(asteroids and KBOs). Jupiter, in fact, throws almost all the ...
5
votes
0
answers
69
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Type Ia supernova by fallback?
Is it possible for a massive star of more than 1.4 solar masses (probably around 3 or more but below the threshold for type II) to collapse into a white dwarf and a planetary nebula, then go supernova ...
5
votes
0
answers
79
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Obtaining the derived period of $\omega$ Canis Majoris
I have read these two papers:
On the nature of the Be phenomenon I. The case of ω Canis Majoris
Stellar and circumstellar activity of the Be star ω CMa
II. Periodic line-profile variability
In the ...
5
votes
0
answers
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 ...
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 (...
5
votes
0
answers
110
views
How often do comet occultations of stars happen?
By travelling to specific places, astronomers can see three thousand star comet transition events every year at m15 for the major (50km+) comets and asteroids averaging about 20 seconds, perhaps that'...
5
votes
0
answers
123
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How is the age of a star on the Henyey track calculated?
I was reading Stellar Evolution in Early Phases of Gravitational Contraction, by Chushiro Henyey, where he writes,
If $L \propto R^{-\alpha}$ along the path, the age of a star from the time when $R=...
4
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0
answers
194
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'Star' appeared dimmer and dimmer over multiple days before disappearing. What could this have been?
This happened a little while ago but I've just been thinking about it!
I was in Wales for a holiday, and over the period of 7 days, a particularly bright 'star'(or at least a bright dot that looked ...