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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How do magnetic fields mess with astronomers' observations?

Does anyone else watch 'Dr. Becky' on YouTube? Her March 'Night Sky News' video, subtitled 'The biggest black hole burp, a wobbly Milky Way & Betelgeuse is brighter' says that... "Dust and ...
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Explanation about the resonance, mean motion resonance and libration

I am studying for a project the dynamics of multi-planetary system in resonance. I have two questions about this domain. In many articles they speak about 'mean motion resonance', what is the ...
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Strength of core-envelope coupling in stars

For a star with a given Zero-Age Main Sequence (ZAMS) mass, as a function of metallicity how strongly is the star's core coupled to its envelope? I understand that the core-envelope boundary is only (...
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Superconducting space dust; what transient fields could induce persistent current loops?

Science Alert's Superconductivity Has Been Discovered in Meteorites For The First Time quotes from Superconductivity found in meteorites (Wampler et al. PNAS March 23, 2020) The paper describes the ...
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Information on Planetary nebula formed from the death of our star the 'Sun'!

I want to know the expansion rate, composition, mass and density of hydrogen present of a Planetary nebula similar to that which will be formed after the death of our star the sun. Knowing these ...
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Combined mass of binary stars

This is Question 17 from USAAAO Practice Round 2015. The answer is D. It would be best if someone can detail out the workings. In a nearby star system, two stars are seen to orbit each other every ...
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53 views

Cosmology : Formula for the bias of galaxies

first I have posted originally on the physics stackexchange but I have not had answers about my question, so I try my luck on this specific forum (if forums leaders want to delete the original post on ...
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205 views

Total number density of galaxies and problematic expression in practise

This post comes from physics exchange forum, I have transfered it here, maybe I will be luckier since I have not received answers on the other forum. Here is the issue : I am asked to give the ...
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219 views

Why the Hubble constant is so inconsistent?

Having a look on Wikipedia I noticed the following values (of the last 6 years) for the Hubble constant: 67.6±0.7 SDSS-III Baryon Oscillation Spectroscopic Survey 73.00±1.75 Hubble Space ...
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141 views

What is the spectral power output of a typical galaxy?

I'm looking for a function which gives the typical isotropic spectral power of light emitted by an entire galaxy on the whole electromagnetic spectrum (in watts per frequency unit), as a function of ...
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248 views

Angular momentum in planetary disk formation

Reading about the formation of planetary disks, one of the major problems, it seems like, is the evacuation of angular momentum. Aparently planets can't form with the amount o angular momentum the ...
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28 views

How thick are the intergalactic filaments?

Recently, in October, news came out about the faint intergalactic filaments finally being 'found'. Then, in June, astronomers announced that these things had enough normal matter in them to solve the '...
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To find the mass and radii of hill sphere of a planet after passing through a region of planetary nebula

Consider a planet with initial mass m* kg and radii of hill sphere as r*. The planet it traveling (assume) perpendicular to the nebula at a speed of 13km/s and the nebula is approaching the planet ...
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How common is it for large objects (few kilometers wide) in a young protoplanetary disk or debris disk to collide with one another?

If enough time has passed for gravitational forces to allow the formation of planetesimals(proto-planets) in orbit around the proto-star, how likely is it that two of them would collide with one ...
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Spectral Energy Distribution (SED) characteristics of Disk and Elliptical Galaxies

Quick questions about the spectral energy distributions of galaxies: What characteristics do we look for in SEDs that provide information on that galaxy's morphology? For example, in spiral galaxy ...
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79 views

Force to fix $\sigma_{8}$ or $A_{s}$ for Forecasts

In the context of Forecasts with Fisher's formalism, I make vary cosmological parameters to compute the elements of the Fisher matrix. First, I generate with CAMB code a linear power spectrum. Then, ...
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85 views

Can “rock stars” form from interstellar dust?

Imagine a large and massive dust cloud made of solid phase micrometeoroids, asteroids and larger planetoids, all material in it is in solid phase, and contains no hydrogen or other volatiles in gas ...
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37 views

Is there a way to calculate how much damage black hole merger shockwaves inflict on nearby objects?

Black hole mergers lose respective rotational energy during a merger. I understand that the energy 'emitted' is scattered as gravitational 'energy' that can henceforth be detected by gravitational ...
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What is the meaning of ellipticity of a galaxy being more than 1?

I was recently doing a project on calculating ellipticities of galaxies using SDSS data. I downloaded the stokes parameter values (q and u) from data $e = 1 - \frac{b}{a} = 1 - \frac{1 - \sqrt{Q^2 + ...
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47 views

How to write a normalized, dimensionless form of Binet's relativistic equation?

$$\frac{\delta^2 u}{\delta \theta^2} + u = \frac{\mu}{h^2} + 3 \mu u^2$$ This is Binet's relativistic equation. Here $u = 1/r$ where $r$ is the radial distance, and $\mu$ is the reduced mass of the ...
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What are the procedures and protocols to use with Gauss'method and personal observations?

I would like to use the Gauss' method to determine the orbit of planets of solar system. I would like to calculate their orbits with personal observations. What is the methodology/procedure/protocol ...
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54 views

What's the profound reason(s) why the star formation rate drives the scatter of the mass-metallicity relation in galaxies?

Since decades it's well known that a correlation between stellar mass and metallicity (Z; both stellar and gas-phase Z, but here I focus on the gas-phase Z) exists (e.g., Tremonti+04; analysis of >...
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78 views

What is known about the angular momentum distribution within galaxy clusters?

I recently saw a 3D-plot of proper motions of galaxies within the Laniakea super-cluster (https://sketchfab.com/models/754cb85550fb42588175f8a215718521). Is a similar 3D map of the vector field of ...
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174 views

Why does the axial tilt & the rotation speed of Saturn & Jupiter vary so much?

I have seen Jupiter and its 4 largest moons in a telescope, several times. The moons are always aligned in a line. This is fine. Very interesting. But.. in case of Saturn, not only that we can see its ...
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Help With Transit Radio Telescope Data Analysis

My high school teacher and I recently built a 10 ft. mesh dish transit radio telescope. In order to compete this year at Nationals for our science fair, we came up with the idea of using a bluetooth ...
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2k views

What is meant by ionization states?

I am going through the theory of saha equation but I am not able to understand the concept of ionisation state? What are ionization states actually?
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27 views

What is the 'scale factor' equation for a dark-matter dominated universe?

The Friedmann equations can be solved exactly in presence of a perfect fluid with equation of state $${\displaystyle p=w\rho c^{2},}p=w\rho c^2$$, where ${\displaystyle p}$ is the pressure, ${\...
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Do apparent magnitude (V) and photometric magnitude (specifically in optical V band between 500-600 nm) have a similar scale to stellar magnitude?

I'm graphing a table and I used the magnitude values from this database https://vizier.u-strasbg.fr/viz-bin/VizieR-4 (It's the V/19/data catalog for "Masses and Ages of stars in 68 open clusters&...
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16 views

Demonstration of scales for the two components (transverse and perpendicular) of Baryonic Acoustic Oscillations (BAO)

I transfer here a post that has not had any answer pn physics exchange, so I am going to delete this latter. Maybe I will have more luckiness here. In an astrophysics context about BAO (Baryonic ...
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10 views

Question about mass growth rate for individual planetesimals

In one stage of classic accretion, the mass growth rate with time (dm/dt) for individual planetesimals is proportional to $m^{2/3}$ and in another stage it is proportional to $m^{4/3}$. My question is ...
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23 views

Supernova impact on Protostar formation

What would be the impact on the formation of a new star (protostar) when a nearby star (within 10 LY) goes supernova? Will the force of the explosion (once it arrives in the Molecular Cloud where the ...
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37 views

What are good resources to study Gravitational Waves?

I am undergraduate student having basic knowledge of Physics. I'm looking for resources (books, video lectures, research papers, etc) to study Gravitational Waves from scratch, I think initially I ...
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25 views

Doppler Shift Vs Gravity Assist for Frequency Shifts from Rotating Galaxies

Frequency Shift of Light Leaving Rotating Galaxies: Differences in Doppler Shift due to Radial Velocity Vs Frequency Shift due to Gravity Assist from a Rotating Galaxy A description of estimating ...
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100 views

Three Body Problem

I tried to solve the three body problem numerically. While after 1000 time steps the system looks stable (See Fig.1) it is completely unstable after 10000 time steps (See Fig.2). Is that an intrinsic ...
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192 views

To show perihelion precession motion of Mercury in Python with matplotlib

I'm trying to make it more general code so I can trace even a parabola or hyperbola for $e=1, E=0$ and $e>1, E>0$ respectively. And after achieving that general code I want to make the same code ...
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What could be observed with LOFAR in 230 MHz - 10.0 MHz wavelength?

Nuclear astrophysics greatly interests me and i was wondering if there is something that could be observed with the LOFAR project in this wavelength that would benefit the field? Also some general ...
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82 views

How to convert Log(g) vs T_eff to y vs (v-y)?

I have a plot in Log(g) vs T_eff coordinates from my stellar evolution model. The parameters of the model are M=0.8 M_solar, [Fe/H]=-1.19, Y=0.245. I want to convert it to the y vs (v-y) coordinates (...
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A high-temperature isolated neutron star could be super-Eddington?

If the surface temperature of a young neutron star is hot enough, say, several KeV, its blackbody radiation could be super-Eddington? Did any paper discuss this scenario before?
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Why does D4000 affect stellar age?

From my understanding D4000 is a ratio between the 'flux densities between 4050 and 4250 Angstroms and that between 3750 and 3950 Angstrom', from Poggianti et al (1997). However I do not understand ...
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Question about finding energy density of a fermionic-bosonic gas

We know that energy density is given by this formula: $$u = \frac{1}{V}\int_0^\infty\epsilon_pf(\epsilon_p) g_s V/h^3 4\pi p^2 dp$$ Where $\epsilon_p=pc$ for relativistic particles. also $f(\...
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How does one interpret the definition of “accretion” in galaxy formation?

I am having trouble finding a solidifying definition of accretion when it comes to galaxy formation models and galaxy evolutions. Where as, in the context of satellite galaxies, dwarf galaxies, or ...
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36 views

magnetic shield for spacecraft outside of Earths shield

I'd like to know if it's possible to create a strong enough onboard magnetic field, similar to Earths' that would protect deep space spacecrafts from the solar wind?
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47 views

DESDM COADD image access

I'm just starting a project to analyze some of the images obtained from the Dark Energy Survey (DES), and I'd like to get some of the COADD images from the SV data. For example, this paper: https://...
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1answer
125 views

Mass of the universe

How do we calculate the mass of the universe taking into consideration dark matter? Mass of visible matter can be computed by stellar method, but how do we calculate mass of dark matter which we don'...
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1answer
233 views

How to compute the perihelion precession of Earth's orbit?

I want to simulate the perihelion precession of Earth. I tried searching other posts in stack exchange as well relating this question but may be it's my fault that I couldn't understand their answers....
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1answer
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Can a pulsar also be a magnetar?

I know this is a simplistic question, but I cannot find a straight answer... Also, is it possible most or all neutron stars are magnetars and/or pulsars? It's just hard to see all of their properties ...
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What features are different in old/young galaxies, what can be seen?

As you all know, the further the galaxy is from us, measured by redshift, the younger it is supposed to be, but what other features can be seen in those younger galaxies to confirm their age? Hints: ...
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What was the energy/wavelength/frequency of the CMB when first emitted/released?

Given the z redshift of 1089, and the temperature difference between then and now of about 1089, I tried scaling the ev, freq. and wavelength by 1089.... Is that right? I get a freq. of about 240 ...
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17 views

How to determine arrival time delay given dispersion measure?

In an online textbook, the following formula is given to calculate the arrival time delay between two frequencies, $v_1, v_2$ in a dispersed radio pulse: $$t_1 - t_2 = 4.15 \cdot DM [(v_1/\text{GHz})^{...
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19 views

Why do exoplanets a little more massive than Earth, often appear to have lower densities than Earth from transit measurements?

Why do exoplanets a little more massive than Earth, often appear to have lower densities than Earth from transit measurements? Assuming that that they are terrestrial planets, what four(I am also nore ...