Questions tagged [astronomy]
The science dealing with objects and phenomena located beyond Earth. In particular, this applies to observations and data. At its core, astronomy is the physically informed cataloging and classifying of the contents of the universe in order to better understand what is out there.
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Derivation of the coherence length of the light coming from a star
Consider a star perceived under an angle $\alpha$ from the earth. In the Hanbury Brown Twiss experiment, they say that the coherence length $L_{coh}$ of this light is given by
$$
L_{coh}= \frac{\...
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What is the reason for slanting of (Solar) analemma?
Why is a (solar) analemma, photographed (Multiple exposure imagery)in the morning or afternoon at latitudes other than geographical poles or the equator, slanted?
(For further examples of slanting ...
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How do you find the extinction coefficient for Gaia photometry?
I have Gaia photometry g, bp, and rp. My final goal is to find the photometric temperature but first I need to account for reddening by finding the extinction coefficient. I’m really stumped on how to ...
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Is the speed of Earth's spinning constant over a given 24 hours?
Is the speed that the Earth spins on its axis constant over the course of 24 hours?
As opposed to does it turn faster and slower during different hours over any given day even by a very small ...
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Does the Earth's magnetic field lag behind the Earth as Earth orbits the sun?
I imagine that when the earth orbits the sun, the earth's magnetic field is also subject to the sun's gravity, since photons and light are subject to gravity. As a result, the magnetic field does not ...
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Measured Value of Hubble's Constant [duplicate]
As we know, Hubble's Constant is not exactly a constant, but its value varies with time. However, we also speak of measuring its present-day value. The measurements by cosmic distance ladder would ...
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How fast do I have to fly vertically up to pause sunset?
I'm standing on the famous Laguna Beach in southern Los Angeles to watch the sunset on December 18th (33.541679°N 117.777214°W, 0m elevation, 16:44 PST). Now, from my perspective at the shore, the sun'...
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What math predicted the eclipse of Betelgeuse?
It's amazing that scientists can predict something as small as last weeks eclipse of Betelgeuse. The general relativity aspects are quite specialized. Can someone point me to the math involved in ...
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Advantage of a single large telescope over many small ones for optical/infrared spectroscopy?
In a thought experiment where we would like to do optical/infrared spectroscopy on distant galaxies, and in which we would like to increase as much as possible the resolution of the spectroscopy (...
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Does average length of sidereal day change if earths axis is tilted in different way
Can precession of axis of rotation of earth cause change in average sidereal day length?
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Is differential number density the same as flux density?
I'm trying to convert the differential number density of photons to luminosity (using slide 17 of https://www.astro.rug.nl/~sctrager/teaching/OA/Photons.pdf) and ...
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How do I approximately calculate the sidereal time at an specific location in a specific time and month (no year)?
How do I approximately calculate the sidereal time at an specific location in a specific time and month ? Most formulas required to input a year too, and then they want you to deal with Julian day, ...
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Why is the time from vernal and autumnal equinox different than from the autumnal to the vernal one?
In my lecture the professor stated that the time from vernal to autumnal equinox is about 186 days , while that from autumnal to vernal equinox is about 179 days.
I was wondering why are these time ...
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How to measure the ratio of a planet's radius to a star?
I was reading a physics problem related to astronomy, and upon re-reading it, I realized that it could be really indicated to extrapolate some really interesting physics-related information.
One of ...
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Paradox about white dwarfs and ionization
I am facing a dilemma. The fact that matter is ionized allows ions and electrons to be much closer together than they are in atoms (Bohr radius $a = 0.5 \cdot 10^{− 10} \mathrm{m}$), and the result is ...
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