Unanswered Questions
162 questions with no upvoted or accepted 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 ...
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7
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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
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7
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1
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What's the safe distance from a hypernova?
Hypernovae are even rarer than supernovae, occuring in stars at more than 30 solar masses, destroying the star that goes hypernova. This post states a hypernova releases several million times more ...
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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?
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5
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When's the most recent time that we could have missed a supernova?
I know that if a supernova were to happen in the galactic Core, the dust there would prevent the visible light from it from reaching us, so if one were to have occurred there in say 1900, we wouldn't ...
- 17.3k
5
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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 ...
- 6,684
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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) ...
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5
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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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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 (...
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4
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If a Milky Way supernova were to happen, how long would it take for astronomers to be notified?
If a Supernova were to happen in the Milky Way, how long would it take for astronomers to be notified?
How long would it take for the people running the gravitational wave and neutrino detectors to ...
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4
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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 ...
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4
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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
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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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How do you know that the remnants of the explosion of a Star are of a Hypernova?
Some Background?
There are many types of Supernovae that can be classified into the following categories :-
(This list is available here.)
Type 1A supernovae
• Their spectra show very little hydrogen ...
4
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How many galaxies have had their distance determined using SNIa?
Supernovae of type Ia can be used as standard candles to determine extra-galactic distances. But these event only occur (roughly) once every 200 years in any given galaxy and rapidly fade away. So to ...
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