Skip to main content

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.

Filter by
Sorted by
Tagged with
0 votes
1 answer
12 views

Mathematical modeling of the influence of components of the interstellar medium on the distortion of the wavefront of the observed object

Associated with: Flowchart of the pipeline of key processes for modeling wavefront distortion of astronomical objects: ground-based observation case Let's imagine for a moment that we are outside the ...
ayr's user avatar
  • 795
0 votes
0 answers
6 views

Flowchart of the pipeline of key processes for modeling wavefront distortion of astronomical objects: ground-based observation case

Associated with: Mathematical modeling of the influence of components of the interstellar medium on the distortion of the wavefront of the observed object Being inspired by this article, as well as ...
ayr's user avatar
  • 795
1 vote
0 answers
13 views

cross-matched SDSS-WISE catalog

Please where can I find cross-matched SDSS and WISE dataset for a machine learning project? (Galaxy-star-qso classification task)
Fanoela Rabemanotrona's user avatar
0 votes
2 answers
133 views

Do all photons coming out of the Sun go out radially?

I am trying to understand why we can assume that all light rays from the Sun are in parallel.
Curious Cat's user avatar
2 votes
0 answers
77 views

Would we know if the universe was rotating?

I was wondering what we would observe if the universe had a small rotation. My conclusion was that galaxies on the equatorial plane of the universe would be slightly more redshifted than galaxies than ...
KDP's user avatar
  • 373
2 votes
2 answers
55 views

Computing error bar for vertex of parabola-fit lightcurve

I have a long-term lightcurve for my source, to which I have used orthogonal distance regression to fit a quadratic model [expected flux]=a[year]²+b[year]+c. Part of our data analysis includes finding ...
HobbitJack's user avatar
-2 votes
0 answers
47 views

What is correct frame of reference for centrifugal force on planet?

How to correctly compute centrifugal force on object laying on equator of rotating planet with no axial tilt? I think there are two possible answers. First is that if the planet rotates so that one ...
Martin Stránský's user avatar
8 votes
1 answer
559 views

References about neutrinos getting clumped in "structures" in the future?

I was wondering whether (standard model) neutrinos could form clumped structures (like halos perhaps). The problem with this is that neutrinos have a very light mass, have a great speed and do not ...
vengaq's user avatar
  • 1,017
-1 votes
0 answers
68 views

Spinning black holes and ring singularities

2 days ago, I asked this question on the physics stack exchange: https://physics.stackexchange.com/questions/815217/what-happens-to-the-ring-singularities-when-two-kerr-black-holes-merge?. However, ...
Flamethrower's user avatar
2 votes
2 answers
107 views

python question-discrepancy between number of stars found

Ok, I get that this is a long question but it's ok if you don't know just thought I'd give this a try anyway. I get that it's a long shot. Basically I'm trying to replicate a methodology used in the ...
Rjs2312's user avatar
  • 29
3 votes
0 answers
41 views

Why MIT's Benjamin Rackham says "nearby ultracool dwarf SPECULOOS-3" would look "purplish-red, spotted, and flaring" from an airless orbiting planet?

May 15, 2024 MIT News article Newly discovered Earth-sized planet may lack an atmosphere includes the following: “We can say from our spectra and other observations that the star has a temperature of ...
uhoh's user avatar
  • 30.6k
0 votes
0 answers
34 views

Project Analog Hypothetical Planet

For my story Project Analog, I was wondering if a hypothetical planet (Let's call it Suria). It has the same size and conditions as Earth with the same axis, tilt, and rotation, as well as one moon. ...
Caemaster117 's user avatar
2 votes
0 answers
98 views

What would the Big Crunch theoretically look/feel like?

In the Big Crunch theory, the expansion of the universe reverses, resulting in all matter contracting into a single point. Imagine you are alive at the time of this event. What would the sky look like?...
value1's user avatar
  • 29
2 votes
1 answer
40 views

How to estimate perturbations from other planets in Apsidal Precession

I am developing a fictional system which I want to calculate to as much detail as I can. Thus I have a question about astrophysics and astrophysical formulae. I know that Apsidal Precession is ...
DanceroftheStars's user avatar
5 votes
1 answer
204 views

Relative inclination with respect to line of sight

I'm encountering some difficulty understanding the concept of line of sight inclination. Typically, we assume that the observer is positioned perpendicular to the system being observed. Consequently, ...
RKerr's user avatar
  • 195
4 votes
1 answer
537 views

Can an astronomer fully work remotely? [closed]

My question today is addressed to those astronomers who have quite a lot of experience working remotely. In general terms, the answer to the question includes the following elements: the range of ...
ayr's user avatar
  • 795
0 votes
3 answers
118 views

How long would a day be in an earth like - same size and all - planet but with double earth's orbit in time

I'm a writer, so I apologize in advance. On an earth like planet with and orbit double to ours in days, how long would days be? My planet would take aproximately 672 earth days to orbit around it's ...
shieldedtulip's user avatar
5 votes
3 answers
2k views

Is the gravitational constant really constant over our Universe?

For instance, if objects are travelling at relatively high speed around 'c', is G the same value for them as for us on earth? I believe a lot of matter is travelling fast away from other matter, so is ...
Bryan Major's user avatar
2 votes
1 answer
106 views

Earth-Moon receding-approaching cycle?

I made the following question in an another more informal forum of discussion on physics: My question comes after reading this article: https://www.coastreporter.net/in-the-community/the-moon-is-...
vengaq's user avatar
  • 1,017
4 votes
1 answer
81 views

How to speed up REBOUND python simulations on a Jupyter notebook?

I'm running Python based computational astrophysics simulations on a Jupyter notebook, with the help of a library called REBOUND (also using REBOUNDx), to create a simulation containing the solar ...
poseidon24's user avatar
6 votes
1 answer
112 views

Why does a white dwarf sometimes go 'nova' and sometimes supernova (type 1a)?

Obviously, when a white dwarf goes truly supernova, there is nothing left, not even, I have heard, a neutron star or black hole... But when certain white dwarf stars accrete certain amounts or types ...
Kurt Hikes's user avatar
  • 5,177
2 votes
0 answers
34 views

Local anisotropies in the expansion of the universe and tidal forces...?

In the context of the large-scale structure of the universe, there can be local anisotropies (https://www.aanda.org/articles/aa/full_html/2021/05/aa40296-21/aa40296-21.html). I understand from this ...
vengaq's user avatar
  • 1,017
7 votes
2 answers
597 views

Why do red dwarf (M-type) stars give off such violent flares and CMEs, out of proportion to their size and temperature?

Dr. Becky (Smethurst) just posted a new YouTube video mentioning, as I have heard many times, that it might not be possible for life to form on planets around Red Dwarf (M) stars because they would ...
Kurt Hikes's user avatar
  • 5,177
2 votes
1 answer
70 views

Expanding voids ending being collapsed?

According to some papers I've found 1, 2 expanding voids can be foun inside clouds of denser materials that can cause them to eventually collapse. I have two questions about this: Overdensities ...
vengaq's user avatar
  • 1,017
2 votes
1 answer
108 views

Open problems in astronomy that a BSc. could contribute / attempt to solve?

From this related question: Open problems in astronomy that an amateur (with a PhD in some other field) would have a chance of solving? What are some open problems in astronomy that an amateur would ...
nuwe's user avatar
  • 771
9 votes
6 answers
4k views

Why don't we just unshift the IR photos from Webb?

I’ve been going back and forth with peers on why image processing is done the way it is on the Webb Telescope. Based off some article, my understanding is that they have various filters that represent ...
lumenhippo's user avatar
0 votes
0 answers
23 views

Deriving Faber-Jackson Relation from Milgrom's Law

I am reading Famaey & McGaugh 2011, a review paper on Modified Newtonian Dynamics. My question concerns bullet 3 in Sec 5.2, where the authors try to explain how Faber-Jackson Relation can be ...
Ambica Govind's user avatar
1 vote
1 answer
73 views

For detection of distant galaxies by gravitational lensing-induced magnification, roughly what are the distance ratios from the lensing systems?

Discussion in comments under the question Does seeing a gravitationally lensed/magnified galaxy imply that they could also see us as well? have got me wondering about the geometry behind detection of ...
uhoh's user avatar
  • 30.6k
-2 votes
1 answer
163 views

Why is v lowercase and D uppercase in $v=H_0D$?

Why is v almost always written in lowercase and D in uppercase in $v=H_0D$? OK, v is in lowercase, as usual, but then why is D in uppercase? What's so different/special about it? In my physics school ...
Curious Cat's user avatar
4 votes
1 answer
175 views

Mysterious factor of 30 in Coulomb cross section for electron–electron collisions

I’m a bit stuck trying to understand where a numerical constant in an old paper comes from. The number in question is in eq. (A1) in Shull & van Steenberg (1985) (which gives the cross section for ...
Socob's user avatar
  • 273
0 votes
1 answer
90 views

Does a cosmological redshift occur within our local group, of galaxies?

I know that it is not supposed to be expanding but space is space and it is expanding everywhere else outside it so why not inside it too, and gravity just holds everything back. I suppose if it is, ...
Curious Cat's user avatar
1 vote
2 answers
1k views

How can Hubble's original data show that the universe is expanding?

The diagram from Hubble's original data only goes from 0 to 2 Mpc (see here), and yet our Local Group is not supposed to be expanding and it is 1.5 Mpc in radius. How can the data show that the ...
Curious Cat's user avatar
2 votes
2 answers
253 views

Fractal structure of the universe

I decided to return to the question first written here after some time, since a short and succinct phrase had formed in my head that described the phenomenon that I was trying to understand. What are ...
ayr's user avatar
  • 795
2 votes
1 answer
133 views

Why are distant type Ia supernovae dimmer than expected?

Why are the (extremely) distant type Ia supernovae dimmer than expected? Relative to what? Their cosmological red shift? Well, what else. Please don't just say "Because the expansion is ...
Curious Cat's user avatar
1 vote
0 answers
119 views

Determining Time Based on Arc Seconds

So our arc day starts at 20°41'32 which is midnight (0:00) and ends 24 hours later at 21°42'42. According to my calculations it traveled 0 degrees, 59 minutes, and 30 seconds or 3570 arc seconds in 24 ...
dimitri33's user avatar
  • 167
4 votes
1 answer
386 views

How to calculate the number density of electrons?

I am trying to calculate the number density of electrons (number of electrons/m^3) for a white dwarf, knowing these parameters : the mass and radius of the white dwarf (therefore its density (kg/m^3))...
Jean Pégoud's user avatar
0 votes
0 answers
66 views

Flux from the Sun on the Earth using the Stefan-Boltzmann law

What is wrong with this computation, plase? I am getting the result of 4291.65 W m^{-2} instead of 1361 W m^{-2}. Thank you very much ...
Anna-Kat's user avatar
  • 505
0 votes
0 answers
46 views

Consistent values for density of galaxies between degree squared and steradian

I have a table of densities of galaxies : Expected number density of galaxies for photometric survey per unit area and redshift intervals, $\mathrm{d} N / \mathrm{d} \Omega \mathrm{d} z\left[\mathrm{...
guizmo133's user avatar
2 votes
1 answer
123 views

Hierarchy of gravitational interactions of astronomical objects: from single to large-scale structures

Hierarchical structure is clearly visible in the Universe. The "observable universe" includes almost empty voids, between which lie large cosmic filaments. The filaments consist of galactic ...
ayr's user avatar
  • 795
2 votes
1 answer
280 views

The Poynting Robertson Effect

In the Poynting Robertson effect, it says in general, the Poynting Robertson effect is caused by the fact that objects like dust re-emit the light they absorb. Is that correct? Is this effect weak? ...
A Curious Mind 's user avatar
1 vote
0 answers
24 views

What would be the new Equation of motion if the magnetic field's origin is shifted from the origin of a co-rotating spherical polar coordinates?

The equation of motions due to the dipole magnetic force of a planet in a frame corotating with the planet and origin at the centre of planet assumed to be sphere components wise are given as below: \...
Lunthang Peter's user avatar
0 votes
2 answers
183 views

What happens to a binary star system when one of the stars explodes and loses a lot of mass

If one star of a binary system explodes and leaves a remnant. The remnant would still have the velocity but lack the mass of the original star.
Michael Mcgarry's user avatar
0 votes
0 answers
33 views

How to plot different curves in the same polar cordinates in matplotlib?

I tried to plot the paths of particle of different sizes in the same polar coordinate using the code given below using matplotlib. somewhat like this: Instead I got this plot: while the path for ...
Lunthang Peter's user avatar
4 votes
1 answer
112 views

How do various astrophysical models deal with so many orders of magnitude in scale? Are there completely different models for different scales?

If we just model our solar system's dynamics, one could use a straightforward numerical integrator with all n(n-1)/2 gravitational interactions along with some torques and non-gravitational forces. ...
uhoh's user avatar
  • 30.6k
2 votes
0 answers
70 views

How is an index of n=0 possible for the Lane-Emden equation?

I was recently showing that an index of $n=0$ for the Lane-Emden equation results in constant density throughout the star. However, in my calculations I had to use the constant $\alpha$ which can be ...
Kian31's user avatar
  • 21
1 vote
1 answer
365 views

Would water freeze on Neptune?

Someone told me that water would boil on Neptune because of the pressure. But this seems suspect to me. Given a temperature of -353 Fahrenheit, I'd expect water to freeze pretty much instantly. So ...
PhysicsNoob's user avatar
3 votes
1 answer
88 views

If a cluster of stars in dynamical equilibrium falls into a much larger blob of dark matter, will it get hotter and expand? Will it stop?

This question is inspired by ProfRob's inspiring answer to Are there really confined Globular Clusters? in which he invokes the concept of "virialization" where a dynamical system reaches ...
uhoh's user avatar
  • 30.6k
1 vote
1 answer
79 views

Gas mass and velocity in galaxy

I was going through the SPARC data on galaxies (http://astroweb.cwru.edu/SPARC/) The velocity of gas in the SPARC data is in http://astroweb.cwru.edu/SPARC/MassModels_Lelli2016c.mrt The gas velocity ...
Angela's user avatar
  • 221
1 vote
0 answers
37 views

What is value of charge by mass ratio (q/m) for a spherical micro charged particle with surface potential 6 volts in S.I units and in e/amu units?

In Liu and Ip (2014),The Astrophysical Journal, 786:34 (8pp), the value of q/m is derived as follows : "for a dust grain with radius 'a', from $\phi = \frac{4\pi q}{\varepsilon_0 a}$ we have $\...
Lunthang Peter's user avatar
0 votes
0 answers
52 views

Crop a FITS file in shape of another

I have a FITS file, let us say file A. I have another FITS file, file B. File B has a smaller footprint than file A. I want to crop file A in shape of file B. How do I go about doing that?
SlightDecoy's user avatar

1
2 3 4 5
14