Questions tagged [astrophysics]

Questions involving the physics of the universe, especially the nature of astronomical objects, energy fields, and/or regions, rather than their positions or motions in space.

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26 views

In shear component $\gamma_1, \gamma_2$ of weak lensing, Why does the defining with $2\phi$ reflect "real angle"?

From the review paper Bartelmann and schneider, 1999) [Weak Gravitational Lensing], page 48. Like above, $\gamma_1 \equiv \mid \gamma \mid cos(2\phi), \gamma_2 \equiv \mid \gamma \mid\sin(2\phi)$. we ...
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43 views

How porous can a terrestrial planet get before it turns into a mini-Neptune?

For reference: A terrestrial planet is a planet that is made out of silicates and metals. A Mini-Neptune is, as far as I know, the smallest type of giant planet (arguably, not even giant), and a ...
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2answers
238 views

Do the newly-created deuterons in our Sun release any photons? In addition to a positron and an electron neutrino?

Perhaps this is a nuclear physics question, but.... When two colliding protons deep inside our Sun finally turn into a deuterium nucleus or deutron (after approximately ten octillion chances, on ...
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0answers
6 views

How do satellite motors keep themselves cool and lubricated? [migrated]

I'm a high-schooler and today we were taught about the car engines and we were told that in order to maintain proper lubrication in order to reduce the heating effect of friction in the pistons using ...
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0answers
16 views

What are all the contributions to libration; is there a self-consistent formalism?

If I understand correctly, in a two-body system with at least one of them more-or-less tidally locked (mean rotational period = mean orbital period) if we draw a line between the centers of mass and ...
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0answers
65 views

What will happen because of the energy release and pair production during collapse a Kerr black hole Inside its event horizon to the limit? [closed]

The release of energy inside the event horizon of a black hole during its continued collapse under gravity towards the theoretical singularity could cause significant deviations from the simple "...
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1answer
85 views
+100

Finding the Laplacian of the deflection potential: I obtain 4𝜅(𝜃⃗ ), not 2𝜅(𝜃⃗ ). Why am I wrong?

From the review paper Bartelmann and schneider, 1999) Weak Gravitational Lensing, page 48. Like above, the Laplacian of the deflection function is convergence, $\kappa(\vec{\theta})$. I tried to ...
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2answers
158 views

Incorrect Mars orbital time while calculating using Kepler formula in Java

Question: I am trying to make a simple java program to do planetary orbital calculation like how many days it takes to complete the orbital along with each Earth day data but I end up getting a 4 ...
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1answer
141 views

What's the difference between the Roche lobe and Roche sphere?

I am just beginning to look into this topic, so apologies if there are any striking misconceptions in the following. From Wikipedia, the Roche lobe is "the region around a star in a binary system ...
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2answers
43 views

How can photoionization release photons? As in the coronal emission of a nova star?

The photoionization process absorbs energy (light), it doesn't release it.... So how can some astrophysicists say that photoionization releases the light responsible for the coronal emission of a star ...
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25 views

Is it possible to infer information about the structure of the universe beyond the observable one?

Is it possible to infer information about the structure of the universe beyond the observable one, by observing its effects on the parts we can see? Can for example gravity from sources we cannot see ...
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0answers
81 views

Beta decay in astronomy [closed]

In what astronomical scenario beta decay happen? I suppose that this process can happen in many astrophysical events, but where is more probable? or is it unlikely to manifest?
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1answer
125 views

How to interpret skewness and kurtosis plots of galaxy snapshots?

What I did:- I am analysing some simulation snapshots of the Milky Way and it is modelled as a dark matter halo – bulge – disc system. I produced some skewness (using ...
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0answers
21 views

Find Periodicity in Lightcurve Using Lombscargle Periodogram(Astropy)

How to find the Nyquist factor for unevenly sampled data like here.https://github.com/jakevdp/PracticalLombScargle/blob/master/figures/LINEAR_Example.ipynb ? I have time binned for 5 mins. I mean for ...
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1answer
77 views

What are the minimum variables that determines the orbital velocity of a planet?

I will try and be brief with this. I want to model a star system in a programming language. It has been a very long time since I did physics. This says that planets have a speed given to them by the ...
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29 views

How rapidly does a main-sequence star become a giant star? [duplicate]

I do not mean when in a star's lifetime it starts to develop into a subgiant, then a red giant, then briefly shrinks again, then becomes a giant or supergiant again, or whatever.... I mean how many ...
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3answers
82 views

What would solar calculations look like in another system? [closed]

When you are determining things (area, luminosity, radius etc) in a star, there are certain things that involve our suns characteristics like solar mass and solar radii. Say I were in another system- ...
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1answer
103 views

Can magnetic monopoles only exist in a curved universe? [closed]

I’m trying to figure out rules for my Sci-fi universe and I need to know what type of universe, the universe needs to be for the existence of magnetic monopoles to exist. I read somewhere that the ...
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2answers
78 views

What's the modification of a parabolic trajectory when accounting for variation in gravity? [closed]

Everyone knows that if you fire a cannon, the cannon ball follows a parabolic trajectory. But that's in an unvarying gravitational field. What if the cannon ball flies so high that one must take the ...
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1answer
51 views

What is the 'AT' astronomical catalogue? And the 'TXS' one? As in AT2019dsg and AT2019fdr?

I cannot find a site stating what the AT or TXS star/astronomy catalogues are, even though some AT and TXS 'events' have been in the news lately....
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0answers
87 views

Cosmology context plotting : Covariance matrix - Script to plot Omega_m vs Omega_Lambda diagram in Python

I have covariance matrices and Markov chains coming from the SCP (Supernova Cosmology Project) and I would like to plot all these data in the particular diagram Omega_Lambda vs Omega_m or w vs Omega_m....
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2answers
201 views

Was the Nobel prize for gravitational waves handed out based on a hand-drawn theoretical curve? Has the data been fit more rigorously now?

In Sabine Hossenfelder's November 2019 video "Have we really measured gravitational waves?" (transcript, video), Sabine mentions the now famous image of the generally agreed-upon-to-be-very-...
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1answer
89 views

Is the sound horizon 500 thousand light years or 500 million light years?

At 06:30 in the nice video Sound Waves from the Beginning of Time about the baryon acoustic oscillations (BAO), the speaker says the sound horizon is about $500$ ...
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1answer
261 views

What is the meaning of integrated emission maps for these chemical species?

In the Astrobites article Spectral Line Survey Reveals New Molecules in Two Protoplanetary Disks integrated emission maps depict the spatial distribution of the flux received from each "line.&...
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3answers
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Can earth grazers skip on the atmosphere more than once?

Earth grazing fireballs are asteroids that enter the atmosphere at a low angle, and skip off it, leaving to space again. Would it be possible that they skip more than once and still leave the ...
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0answers
18 views

Curated dataset of labelled images for NEO detection

I am looking for a dataset of images. Some images should contain NEO's (1 or more), others should not. With the dataset, there should also be an accompanying file, of which should contain 'labels'. ...
2
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1answer
74 views

What does lowercase 'beta' mean in this graph of radio-emitting galaxies?

Correlation between the mass of the galaxies (X-axis) and the difference of their radio emissions at different radio frequencies (Y-axis). Each symbol represents an individual galaxy. The image of an ...
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0answers
15 views

Procedure to construct a spectral energy distribution and bolometric light curve of supernovae?

Can anyone check the logic of this proposed workflow and/or point me in the direction of a guide and example to check my work? Proposed procedure to construct a spectral energy distribution and ...
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0answers
48 views

Why does the 'Big Bang Nucleosynthesis' theory require that neutrinos, or at least sterile neutrinos, have a LARGE mass rather than a tiny one?

From Wikipedia, Sterile neutrino Particles that possess the quantum numbers of sterile neutrinos and masses great enough such that they do not interfere with the current theory of Big Bang ...
5
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1answer
76 views

Are there any spectral lines with smaller frequencies than the hydrogen line?

The 21 centimeter hydrogen line originates from the hyperfine transition of neutral hydrogen. Are there any bigger wavelengths that originate from this method? Radio emissions from rotating stellar ...
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1answer
132 views

Binning a Phase Folded Lightcurve

How do I bin a messy phase folded lightcurve? This is one of the phase folded generated plots for a variable star. I plotted the phase using the period extracted by Lomb-Scargle Periodogram algorithm. ...
2
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1answer
35 views

How long does the "eclipse" last on a space station at the L1 point between a moon and a planet last when the moon blocks the sun in front?

The situation I am asking about is as depicted in the picture. Supposing I have a space station staying perpetually at the L1 point, the moon will completely block the space station from all sunlight ...
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1answer
44 views

Where do Astronomers usually get their wavelengths? Where do they turn to look up standard, accepted values for spectral features?

When identifying isolated observed spectral features or fitting complex observed spectra or even running complex numerical simulations, one needs a reliable, standard table of known wavelengths and ...
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0answers
57 views

Do all C-O white dwarfs have more-or-less the same proportions of carbon and oxygen?

Type 1a supernovae are known for having very consistent energy yields, and they are caused when a carbon-oxygen white dwarf reaches the Chandrasekhar limit of about 1.4 solar masses. Since type 1a ...
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3answers
120 views

How is space a vacuum when there are planets, gases, etc?

Space has a lot of stuff so how can it be a vacuum?
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1answer
107 views

Why do some call the no-hair conjecture the no-hair theorem?

This excellent answer to Why would a black hole's magnetic hair being short-lived not violate the no-hair conjecture, but long-lived hair would? How long is “long-lived”? has got me thinking because ...
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1answer
52 views

Why would a black hole's magnetic hair being short-lived not violate the no-hair conjecture, but long-lived hair would? How long is "long-lived"?

Phys.org's Magnetic 'balding' of black holes saves general relativity prediction says: There is a potentially hairy threat to the conjecture, though. Black holes can be born with a strong magnetic ...
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72 views

Is there a formula for a planet's orbit in a 3D space?

I'm trying to model the orbits of Earth and Mars and their positions at a given point in time. But I can only find 2D equations of elliptic orbits, which only contain the x and y variables. I have to ...
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98 views

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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2answers
185 views

Is a Hertz ratio to 65M ☉ proof that Betelgeuse had a core collapse in 1491 from a gravitational wave on January 14, 2020? [closed]

By analysis of gravity waves GW150914 to S200114f when compared to a ratio from the Black Hole merger of 65 M ☉ at 260 Hz with Betelgeuse frequency of 64.698303 Hz the gravitational release on January ...
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4answers
2k views

How can a black hole have a charge, or be charged?

So-called 'hairless' black holes (no-hair theory, or theorem?) , which is what real black holes are, can be described by just three characteristics: Mass, spin, and charge. It is easy enough to ...
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2answers
439 views

What exactly is the orbital period value of Sirius binary star system?

My Textbook An Introduction to Modern Astrophysics 2nd edition (2017), page 557 mentions that the modern value is 49.9 years. But Wikipedia mentions 50.1284±0.0043 years. Which is correct? Or, has the ...
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3answers
156 views

Learning astrophysics from zero

I'm a liberal arts student, an undergraduate English student who out of the blue, started getting interested in astronomy and physics, searching for facts all the time, googling about some theories, ...
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0answers
26 views

Error of bisector method

How to determine the error of bisector velocity span? I have found the article below, but I do not know what all quantities mean. What is the number of lines in the mask? How to find out x? How to ...
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1answer
332 views

Degrees of freedom in restricted circular coplanar three body problem

How many degrees of freedom does a mechanical system consisting of three bodies, the Sun, Jupiter and an asteroid, have in the restricted circular coplanar problem of the three bodies? I know that if ...
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0answers
46 views

What is the sun's maximum influence on a magnetic object?

How much magnetic repulsion could the sun's magnetic field produce on an magnetic object? Consider the object is ideal: It could be flat, to create more resistance, balanced, to stay on the opposing ...
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3answers
286 views

Role of power laws in astronomy?

I often see astronomers fitting data to power laws. What about power laws makes them so useful in astronomy? Why are so many astronomical observations well-fit by power laws? I know it's a relation ...
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0answers
30 views

Looking for analytical expression of Cosmic Variance - Poisson distribution?

I have an expression of Matter Angular power spectrum which can be computed numerically by a simple rectangular integration method (see below). I make appear in this expression the spectroscopic ...
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2answers
112 views

Is the dark matter just regular matter out of the observable universe?

Could it be that darkmatter is actually the gravitational influence of regular matter that is situated out of the observable universe?
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2answers
85 views

Does black hole singularity really exists with respective to relative frame of reference? [duplicate]

How can one describe this phenomena? What are the factors that we should consider for solving such a problem?

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