Unanswered Questions
1,828 questions with no upvoted or accepted answers
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Angular resolution of naked eye at night; type of vision used
It appears that most sources quote the angular resolution of the eye as 1', regardless of day and night.
For instance,
Naked eye
Seconds of Arc and the Unaided Eye
However, the following websites give ...
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How are the aberrations seen in early JWST images corrected?
I found this image on space.com and it can also be found in NASA's JWST blog. This is one step in the process of aligning the 18 mirrors on JWST. A single relatively-isolated star has been selected. ...
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Convert from Jy/beam km/s to W/m$^2$
I need to compare some ALMA observations of a protoplanetary disk to disk-integrated fluxes obtained from a model.
The ALMA observations are upper limits of non-detected spectral lines, where the RMS ...
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What's the largest angle that light has been "seen to bend" by gravity? (of one object by a separate object)
Gravitational lensing is everywhere! because it falls off so slowly with $r$:
$$\Delta \phi \approx \frac{4GM}{c^2r_0}.$$
That's the first order term. For a nice derivation see Viktor Toth's The ...
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Have auroras on Titan been observed yet?
After reading the very insightful introduction to auroras on other planets I started digging and found various questions and some answers here on the same topic, see below.
What I did not figure out ...
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What effect do aircraft have on night-time visibility?
I have something of an interest in astronomy. I also have a 5" reflector telescope, plus of course binoculars. With the recent coronavirus emergency, a large number of commercial aircraft were ...
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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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How do I calculate the Hill radius of a star in a binary system?
Is there an easy way to calculate the Hill radius of a star in a binary system at different orbital radii where both stars are of the same mass and in circular orbit around one another’s centre of ...
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Detecting a Rogue Planet from Earth
This is for a novel.
A rogue planet, is, by a one-in-a-zillion freak chance, on its way to collide with Earth. It has been drifting in interstellar space since its original formation (billions of ...
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Gravitational eddies across the galaxy?
I read about natural gravitational eddies that travel in a wave that black holes have. They also have a strong magnetic field. Does those eddies follow magnetic field lines of the rotating black hole? ...
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How to calculate the temperature of an exoplanet?
I was given an exoplanet similar in size and distance to host star to our own earth. It's orbiting a star with luminosity six times our sun, the greenhouse coefficient 0.3, bond albedo 0.3.
I would ...
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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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2
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Correct relation between metallicity (z) and iron content ([Fe/H])
The Wikipedia entry on Metallicity states that:
$\log_{10}\left(\frac{Z/X}{Z_\mathrm{sun}/X_\mathrm{sun}}\right) = [\mathrm{M}/\mathrm{H}]$
where $[M/H]$ is the star's total metal abundance (i.e. all ...
CommunityBot
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Radius of hydrogen cloud
I am using a 1.4 meter parabolic dish with HPBW of 10 degrees and a RTLSDR to study our milky way in hydrogen line. The structure of the galaxy is deduced as shown in the picture by plugging the ...
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Hubble tension and Cepheid systematic error
The Hubble tension is the discrepancy between measurements of the local rate of expansion of the universe vs the predicted rate inferred from CMB and the Friedmann equations.
A dizzying array of ...
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