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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What does "by an amount" mean here?

In A Very Short Introduction: Black Holes by Katherine Blundell, the author discusses the emptiness pf the space: One of the surprising consequences of this new theory was that there were fleeting ...
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2 votes
2 answers
55 views

What does "energy dumped into waves" mean?

In A Very Short Introduction: Black Holes by Katherine Blundell, the author discusses the merger of two black holes in a binary system: The energy released in the merger of two supermassive black ...
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4 votes
1 answer
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What does "to within less than about thirty Schwarzschild radii" mean?

In A Very Short Introduction: Black Holes by Katherine Blundell, the author discusses the imaging of plasma jets at the center of black holes: At 50 million light-years from Earth an object moving at ...
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1 vote
1 answer
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following several unknown phenomena detected at the edge of the solar system, is there a 5th force which acts at the edge of the solar system?

following several unknown phenomena detected as the acceleration of Oumuamua and electrons and strange data sent by traveler 1 at the edge of the solar system, is there a 5th force which acts at the ...
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3 votes
1 answer
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What is the goal of predicting gravitational microlensing?

I know that gravitational lensing is a geometric effect that occurs when light changes direction because a massive object causes space-time to warp and consequently the radiation rays change the path ...
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Why do most astrophysicists believe the cosmic microwave background (CMB) provides the best evidence for dark matter? What, exactly, IS that evidence?

I frequently read that the cosmic microwave background contains the best overall evidence for the existence of dark matter, and conversely against alternative gravity theories like MOND. However, I ...
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1 vote
1 answer
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The preferred way of binning (classifying) data for galaxy snapshots in Python

Let's say I have a galaxy snapshot that I load with some package (pynbody etc) and I store my spatial coordinates of stars in the galaxy in x, y, z arrays and also velocity in array vz. Now I want to ...
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2 votes
0 answers
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Is there a cosmological model of the evolution of vacuum motion in our universe over time? [closed]

Is there a cosmological model of the evolution of vacuum motion in our universe over time? Does this model starting from a non-vacuum constitute an advantage compared to the cosmological model of ...
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7 votes
3 answers
661 views

How can I calculate an orbital elliptic trajectory from the velocity vector?

I have been struggling for a few days with this. I know just my distance from gravity origin, gravity source mass and my actual velocity vector on the orbit. Can I calculate whole trajectory with this?...
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3 votes
0 answers
32 views

Explanation for Planck 2018 temperature fluctuations strongest peaks

As it can be seen from Plank 2018 Cosmic Microwave Background temperature fluctuations data- There are 3 sharp peaks at multipole expansions $\ell \approx 250, 550, 800 $. Also as multipole expansion ...
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6 votes
1 answer
113 views

Do “neutrino supernovae” exist?

Core collapse supernovae release most of their energy in the form of neutrinos. About 1% of the neutrinos are absorbed by the thick outer envelope which powers a spectacular supernova explosion. Core ...
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1 answer
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SAO Encyclopedia of Astronomy information

I was reading about destructive interference in the SAO Encyclopedia of Astronomy. For some reason it says the first photo is destructive interference, when clearly, the amplitude increases, so it ...
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1 vote
1 answer
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Stars as nozzles; how important is thermodynamics and the de Laval nozzle equation for understanding the speed of the solar wind vs distance?

Seeing What determines the speed of a star's solar wind? I'm having flashbacks from undergraduate days where the professor started their lecture on solar wind by writing something that they called ...
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4 votes
1 answer
377 views

Using Einsteinpy to plot the precession of a star orbiting a black hole?

I am currently trying to code the precession of a star orbiting around a black hole, the issue I am having though is that I have no clue what the values are and what they mean in the code, if anyone ...
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0 votes
1 answer
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When is Betelgeuse (the shoulder star in the constellation of Orion) going to supernova?

My question is: when is Betelgeuse supposed to supernova? I have been waiting for a while now. Some people say it will explode this year, but I'm not sure. It is getting very close to its supernova, ...
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1 vote
1 answer
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What do the letters WHL and LS stand for in the description and name of Earendel star, and other distant objects?

Earendel star's official name includes the abbreviations WHL and LS, as do some other very far-off objects.... What do they stand for?
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1 vote
3 answers
281 views

Using optical fibers in astronomy

Why are optical fibers important in astronomy? I have read on the internet that they find applications in many fields including astronomy and this intrigued me and I would like to know what they are ...
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0 votes
1 answer
55 views

How is CASA different from SAO DS9?

I was told that CASA is used extensively in Radio Astronomy. However, softwares like SAO DS9 and also python (Astropy) are also used for radio astronomy data analysis. So, what makes CASA different as ...
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3 votes
1 answer
133 views

How does general relativity explain gravity?

General relativity explains that gravity is the curving of spacetime by massive objects. This makes sense, like when I throw a ball, it follows the curve of spacetime, which is towards the center of ...
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6 votes
1 answer
111 views

Declaring of 3C273 as a quasi-stellar object

I am currently reading A Brief History of Time and chapter 6 about black holes. Now, here it says He found it too large to be caused by a gravitational field: if it had been a gravitational redshift, ...
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2 votes
1 answer
101 views

How is it possible that a Big Bang happened instead of becoming trapped as a Kugelblitz? [duplicate]

I was reading about Kugelblitz on Wikipedia, and it says that if enough energy gets concentrated it leads to a black hole (from where nothing can escape - supposedly). So, if during the Big-Bang, when ...
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2 votes
0 answers
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How can a busy high school student get into learning Astronomy?

I'm a high school student that has loved physics for quite some time, but have only started dabbling with the more complex things. I know a fair bit about quantum mechanics and such as I like it, but ...
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1 vote
2 answers
156 views

Astrophysics Ph.D. thesis on intergalactic rogue planets and their habitability; how active is this field of research?

Is the habitability of intergalactic rogue planets something that has been studied a lot? The reason that I'm asking is that I've just started my PhD program last year and I'm wondering/concerned if ...
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3 votes
0 answers
29 views

What is the main difference between cyclotron, synchrotron, and gyrosynchrotron radiation?

How are these various types of radiation generated? What is the main difference between them? Can someone suggest a book related to these radiations?
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4 votes
3 answers
237 views

Great Attractor's gravity vs Universe Expansion

I would like to know if the trajectory of our galaxy has been calculated because it is usually said that the cosmos is emptying due to the expansion of the universe but at the same time there is a ...
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3 votes
0 answers
52 views

Why don’t black holes have an infinite rotational velocity? [duplicate]

We know that blackholes retain the properties of their progenitor, so if we think of the total angular momentum of a blackhole’s progenitor star now in an infinitesimal point (0 radius), should it’s ...
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3 votes
3 answers
158 views

Why does the gas cloud collapse in regions of high density?

Stars form when gas cloud collapse under gravity, becoming hot and subsequently initiating nuclear fusion. I have read that the collapse is triggered by density fluctuations, where regions of high ...
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  • 463
2 votes
2 answers
135 views

What is the relation between Kelvin-Helmholtz timescale and free-fall timescale?

What is the actual difference between these two timescales? Both of these timescales define the time for collapse when there is only gravity. Also, what does it mean by saying Kelvin-Helmholtz ...
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3 votes
1 answer
304 views

What determines the temperature of a white dwarf?

Can someone please explain what determines the temperature of the white dwarf? Is more massive white dwarf hotter ? Also, is the density of a white dwarf always a constant?
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  • 463
1 vote
1 answer
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What exactly is the estimated distance to a far-off object when they say '50 Mpc/h' or '50 Mpc h^-1'? Is it less than 50 Mpc? Do you ÷ by 67 or 74?

Several recent arxiv.org papers I read mention distances to very distant objects in Mpc (megaparsecs) divided by Hubble's 'constant'.... Does that mean we should divide the Mpc or Gpc (gigaparsecs) by ...
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1 vote
1 answer
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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 \left| \gamma \right| \cos(2\phi), \gamma_2 \equiv \left| \gamma \right|\sin(2\...
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6 votes
0 answers
143 views

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

EDIT: well, now I have more 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,...
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5 votes
2 answers
269 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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3 votes
1 answer
118 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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1 vote
1 answer
100 views

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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  • 109
2 votes
2 answers
171 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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6 votes
1 answer
229 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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2 votes
2 answers
46 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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1 vote
0 answers
28 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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1 vote
0 answers
82 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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2 votes
1 answer
142 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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1 vote
0 answers
36 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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0 votes
1 answer
99 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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  • 109
0 votes
0 answers
35 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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  • 3,375
0 votes
3 answers
86 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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0 votes
1 answer
112 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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2 votes
2 answers
79 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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-1 votes
1 answer
57 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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2 votes
0 answers
132 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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0 votes
2 answers
256 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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