Unanswered Questions
238 questions with no upvoted or accepted answers
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What's the angle between the sun's galactic speed and the ecliptic?
I know the sun wobbles up and down the galactic plane around 35myr. I don't mind about that component.
I'd like the know the angle between the linear speed of sun around the Milky Way (just the ...
- 141
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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'...
- 7,684
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From what distances do the atoms in you come from?
If the atoms of a human come from stars, comets, nebulas and magnetrons, then what is the greatest distance that two atoms of a human can possibly have been away from each other previously? Perhaps ...
- 308
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How significant is the effect of galactic rotation on line broadening of carbon monoxide?
In class the other day, we were discussing observations of rotational transitions of carbon monoxide, namely, the $J=1\to0$ and $J=2\to1$ lines. We originally had assumed that both lines would have ...
- 37.3k
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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 ...
- 17.6k
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Cosmology : Formula for the bias of galaxies
first I have posted originally on the physics stackexchange but I have not had answers about my question, so I try my luck on this specific forum (if forums leaders want to delete the original post on ...
- 5,636
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Introduction to the Magellanic Clouds?
I'm looking for an introductory textbook on the Magellanic Clouds, something suited for a student about to obtain their Physics BS degree (ie: not a professional astronomer).
I'm aware of The ...
- 17.6k
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Why the Hubble constant is so inconsistent?
Having a look on Wikipedia I noticed the following values (of the last 6 years) for the Hubble constant:
67.6±0.7 SDSS-III Baryon Oscillation Spectroscopic Survey
73.00±1.75 Hubble Space ...
- 316
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Spectral analysis of AGN (velocity dispersion of galaxy absorption, doppler shifts)
I was wondering what parameters I need to know/measure to calculate the velocity dispersion of a galaxy, specifically an AGN.
Also, I have spectra where there are blueshifted and redshifted ...
- 5,636
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Why MIT's Benjamin Rackham says "nearby ultracool dwarf SPECULOOS-3" would look "purplish-red, spotted, and flaring" from an airless orbiting planet?
May 15, 2024 MIT News article Newly discovered Earth-sized planet may lack an atmosphere includes the following:
“We can say from our spectra and other observations that the star has a temperature of ...
- 30.7k
3
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SExtractor parameters for identifying Star Forming regions
I am using SExtractor (Source Extractor) to identify Star-Forming regions in a galaxy. The problem is I am unable to choose the parameters required for it. SExtractor is just a tool to identify the ...
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Gravitational recoil with stars/planets...?
When two black holes are merging, the resulting merge can be ejected if one of the black holes had less mass than the other one, so the gravitational waves emitted by both of them is unbalanced, and ...
- 1,017
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How do star orbits, density wave theory and dark matter distribution work together?
I got confused while trying to combine these 3 concepts. Would love to hear some detailed explanation.
Density wave theory states that spiral arms are formed by tilted elliptic orbits. Bertrand's ...
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Potential energy in an expanding universe
A question you wonderful geniuses can hopefully answer. Imagine a piece of string drawn between two galaxies. Space between the galaxies is expanding. What force is being applied to the string? Where ...
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Deviations of conservation laws in the context of cosmological evolution?
If energy is "not conserved" in General Relativity (or at least, it is difficult to define it) in the context of an accelerating expanding spacetime (like it happens in our Universe), are ...
- 1,017