Newest Questions
15,667 questions
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How would one take a simulated Gaussian function absorption line and match it to a given spectrograph resolution?
I have a gaussian function to simulate an absorption line, of arbitrary spacing in wavelength (e.g., 1000 - 2000 Angstrom, with Δλ = 0.01 Angstrom).
I would like to 'simulate' what a given ...
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32
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Light Curve to SED - ZTF
I have the light curves of a source from the Zwicky Transient Facility (ZTF) which is magnitude vs time (MJD) plot using g, r and i filters of the ZTF. Now, I have selected a time interval for further ...
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26
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Anisotropic to isotropic term ratio of the radiation field in the LTE plane parallel atmosphere approximation - Choudhuri's textbook
I am reading Choudhuri's book on general astrophysics and in the section on plane parallel atmosphere approximation he writes this
Shouldn't the flux depend on optical depth and therefore only be ...
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2
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81
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When we look towards the galactic centre is the plane of the sky perpendicular to galactic plane? [closed]
I believe Google / Gemini is wrong
No, the "plane of the sky" is not perpendicular to the galactic plane
when looking towards the galactic center. The plane of the sky is the
imaginary, ...
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2
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173
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What is the cutoff between a rocky planet and a gas giant/ ice giant [duplicate]
If I were to take a rocky planet and keep adding gas to it, at what point would it stop being a rocky planet?
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Why aren't Turnbull's 5 Terrestrial Planet Finder stars in the HabCat?
In 2002, Margaret Turnbull and Jill Tartar created the Catalog of Nearby Habitable Systems (also called HabCat), a list of 17,129 solar systems that where we are more likely to find habitable worlds. ...
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Why are aurora viewed from latitudes closer to the equator redder compared to aurorae viewed from more polar latitudes, which are usually green?
Recently there was a CME and I noticed that a lot of the recent images posted from e.g. Florida are like a red or pink glow on the horizon, while photos posted during normal times by people living in ...
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How do neutron/white dwarf stars get close enough to merge?
For a pair of white dwarf/neutron stars of 1 solar mass separated by 2.5 million kilometers, the time it would take their orbit to decay via gravitational waves and the components to merge is roughly ...
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98
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Why don't black holes have 3-sphere surfaces? [closed]
If a black hole is a ball of 4-dimensional spacetime we might expect it to have a 3-sphere surface, but this doesn't seem to be the case. Why not?
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Require sine waves of lunar motion from 1851 to 2025 fitting to earth phenomena for modeling purposes
The following graph is from this post by user PM2Ring:
I am doing a little modeling in Fourier series style fitting the apsidal and nodal cycles. Then Gemini turned up this post, and there are 2 more ...
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Why is Venus almost tidally locked [duplicate]
Venus barely rotates at all. Why is this, it should be just the sun alone. The tidal strength of the sun of Venus is roughly the same as the tidal strength of the moon on the Earth.
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Flat curvature and decelerated expansion in wCDM models
Strong progenitor age bias in supernova cosmology – II. Alignment with DESI BAO and signs of a non-accelerating universe
6 November 2025
Previous paper: Strong progenitor age bias in supernova ...
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6
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4
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2k
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Would it be possible for a moon to be impacted, making it spiral into the planet? [duplicate]
I have read that objects impacting a planet could eventually cause its moon to spiral inwards and crash into it. One such way is if the impact reverses the rotation of the planet, because then any ...
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71
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What is this time dilation adjustment that has to be done for high-z objects? [duplicate]
In knocking down someone's personal Astrophysics theory, @profrob said, "How does it explain the $(1+z)^{−1}$ time-dilation observed for Type Ia supernova curves and gamma ray bursts?"
Does ...
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Where are the foci of Earth's orbit?
The following is a figure from a textbook, it depicts the Earth's orbit in space.
I added the red annotations for the sake of this question.
I know that according Kepler/Newton the orbit is an ellipse ...
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110
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What is meant by the 'King core radius'?
While looking for a parameter that represents the extent of a star cluster, I came across the King core radius ($r_c$). However, even after reading papers, I still don’t understand it. What does the ...
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61
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Could cometary non-gravitational acceleration be linked to surface cohesion transitions?
In several comets, including the interstellar comet 3I/ATLAS, a non-gravitational acceleration is observed, i.e., a net thrust not fully accounted for by gravity. While outgassing is known to produce ...
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74
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Maximum stellar flux for a volcanically active CO₂-dominated planet to retain water
This question is based on the assumption that, during the first several hundred million years, a sufficiently massive planet undergoes vigorous volcanic activity that produces a predominantly carbon ...
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140
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how much does escape velocity vary with location and time?
Launching a rocket to 'space' from Cape Canaveral (at sea level) requires a certain effort, based on gravitational force, and distance from the centre of the earth.
Move the launch up to an Andean ...
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Does an entire flux of neutrinos eventually get absorbed?
Take for example the normal solar flux of neutrinos which is roughly 1010 neutrinos/cm2/s. This would produce 1038+ neutrinos each second.
Neutrinos are iconic for their extremely weak interaction ...
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190
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Could an exoplanet's atmosphere have significant quantities of heavy noble gases?
Earth's atmosphere is approximately 1% argon, which is actually surprisingly small amount, and only trace quantities of krypton and xenon. Argon isn't that rare in the universe, apparently its ...
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72
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Methods for determining the extent of an open cluster
I derived an H–R diagram for M45 using Gaia data by applying a parallax window and an angular radius around the cluster center. However, I chose the parallax window ad hoc around the literature ...
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Converting spectral luminosity density to absolute AB magnitude
I have a spectral luminosity density in ergs/s/Angstrom of a galaxy at a given wavelength 1500 angstrom. How can I get the absolute AB magnitude this corresponds to assuming some sort of cosmology (i....
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130
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S2 orbit - orientation relative to our line of sight
S2 is probably the most observed among the S-stars that orbit around the black hole at the centre of our galaxy.
I'm trying to understand S2 orbit orientation but I'm having hard time with (I suspect) ...
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3
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1k
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Why aren't there green stars? [duplicate]
Stars come in red, yellow, and blue hues.
Yet green stars don't exist.
However, according to Wien's law, the maximum radiation between the red and blue wavelengths passes through the green wavelength, ...
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183
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What are the black regions in this image?
What are the black squares in this region?
It's the Sequoia cluster.
From here
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4
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1
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127
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Separating stellar rotation from stellar activity in spectral analysis
I think I need an Astronomy 101 lesson. I was under the impression that rotation (vsini) is determined by line widths in spectra. It seems that this could also be affected by stellar magnetic activity....
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7
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3
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3k
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Don't all roads lead to heat death?
There have been a number of proposed theories about the fate of the universe. And while the heat death theory is now favored, isn't it simply inevitable? Here's what I mean.
Let's assume a big crunch ...
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181
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What's the difference between Adaptive Optics and Active Optics?
Wikipedia says:
Adaptive optics should not be confused with active optics, which work on a longer timescale to correct the primary mirror geometry.
What's the difference, and which one is higher rez?...
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How do we keep track of the positions of stars that are light years away?
We are moving constantly through space. The universe itself is expanding and therefor moving things around. Now, I always wondered how we keep track of those unbelievably far objects that are on a ...
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203
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Corona of the Sun vs Sun vs Betelgeuse [closed]
Why is the Sun's corona so dim compared to the Sun itself, yet Betelgeuse is much more luminous than the Sun? I've read that Betelgeuse's surface area increases its luminosity, but it doesn't really ...
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1
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Red Shift Puzzle
I understand redshift and how it relates to relative motion, but my question is:
It takes millions or billions of years for light from the most distant objects to reach us here on earth. The most ...
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207
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What will become of Betelgeuse?
Is Betelgeuse massive enough to become a black hole after it goes supernova or will it just become a neutron star? Also has it been proven to be a binary star?
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Standing alone, does the sun itself rotate [duplicate]
Based on earth taking 24hrs to complete 1 full rotation, how long does the sun itself take to complete 1 rotation.
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Help on calculating the sun's horizontal coordinates
For a couple of weeks, I have been trying to write a program that takes your
latitude and longitude and outputs the current horizontal coordinates of the sun.
The end goal is that I want to code a sun ...
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46
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OPALE API request structure to get moon position
I am a non-astronomer computer scientist. I am trying to make a web app that tracks the "position of the Moon vs the Earth". What I mean by this position = trying to determine the location ...
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2
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What is the composition of 3I/ATLAS?
An interstellar object known as 3I/ATLAS is visiting our Solar System.
What is known about its composition? How does this compare to similarly sized (km-scale) cometary objects in the Solar System?
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What is the farthest distance from which auroras on Earth have been observed by humans?
We've seen many photos of auroras on Earth (aurora borealis and australis) taken from the International Space Station, which orbits around 400 km above Earth.
This made me wonder — what is the ...
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1
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Orbital planes of stars in the S-cluster; is any edge-on (or close)?
The S-cluster of stars that move around the Milky Way’s supermassive black hole SgrA*.
S4716 is an interesting one, suggested in the second answer to related S2 "has an orbital period of just 4....
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What do lithium abundance numbers mean in catalogs like Hypatia?
I totally understand the meaning of the chemical abundances given for most elements (e.g., [Fe/H], [C/H], [O/H], [C/Fe], [O/Fe], etc.), but values given for lithium don't make sense to me. For ...
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2
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179
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How to tell if two locations have the same longtitude with naked human eyes
As a follow-up to this question, I was wondering about another scenario. Suppose there is a person who has been living for a few years in Mexico at -103 longitude. Then he migrated to Canada and has ...
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Are objects really attracted towards centres of gravity?
Take three identical objects in space, A, B and C. A and B are separated and C is travelling towards them. If they have negligible mass, C will collide with A or B or pass between them, depending on ...
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How to walk on earth along a line of constant longitude without any technology aid
Assume that we have chosen some particular meridian to traverse on foot in the northern hemisphere. If one could only refer to the night sky, stars, and the sun, how would one be able to move along a ...
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Why are my calculations for the Moonrise time always incorrect?
This question is considered a continuation of the my previous question.
I am following the article stjarnhimlen's Computing the Moon's rise/set times tutorial to calculate the moonrise and moonset ...
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In professional practice, how are unresolved binaries statistically accounted for when deriving stellar mass functions?
Many surveys note that unresolved binary stars can bias stellar mass function estimates. I understand that they can make single stars appear more massive, but I’m curious about the methodological ...
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Astrometry.net plate solving with fish eye lens
I have some images taken with an Oculus all-sky camera that has a fish-eye lens with a 150-degree field of view. I have tried to perform plate solving using astrometry.net; however, it fails to plate-...
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102
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What would the shadow path of a geostationary object be?
If we managed to put an object into geostationary orbit over the Earth that was large enough to cast a noticeable shadow on the ground, what path would that shadow take? I’m wondering both about the ...
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Detecting the Extended Nature of objects via Orbital Dynamics?
Background
So Kepler's second law of equal areas is a consequence of the conservation of angular momentum:
$$L = I \omega$$
where $L$ is the angular momentum, $I$ is the momentum of inertia and $\...
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Alternative explanation of red shift of distant stars? [closed]
I was thinking about an alternate explanation of the red shift of distant stars: An Infinite universe would have 0 average gravity by symmetry.
We only see the near side of distant galaxy clusters ...
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Rotation of a planet orbiting in a polar orbit w.r.t a binary system
I was quite surprised to hear the news of the discovery of 2M1510, a system with a central binary formed by dwarfs on highly elliptical orbits with a planet revolving at almost 90 degrees wrt the ...
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