Questions tagged [astrophysics]

The application of physical theory to celestial systems such as stars, planets, galaxies, supernovae, and black holes. Astrophysics proper is concerned with explaining phenomena more so than making observations, the latter falling under the purview of astronomy.

Filter by
Sorted by
Tagged with
1
vote
3answers
48 views

Why don't the nuclear fusion processes inside the sun produce electron antineutrinos $(\bar\nu_e)$?

Why don't the nuclear fusion processes inside the sun produce $\bar\nu_e$ despite having the same mass as $\nu_e$? Is the reason as simple as "there is no production channel for $\bar\nu_e$s.&...
1
vote
2answers
31 views

What's the reference/original wavelength while calculating redshift?

Measuring redshift is one of the ways of analyzing distance in astronomy, since the redshift of an object is caused by the expansion of space between us and the object, the more space there is between ...
-3
votes
0answers
44 views

What is the Law of 1? [closed]

Is there support from the physics community on the Law of 1 or Ra as proposed by Brian Wilcock in his book the "Synchronicity Key"?
0
votes
0answers
16 views

Readings on Dark Matter [duplicate]

I am looking for introductions and reviews (papers or books) on the possible observation and the nature of dark matter. This book seems to be a good start, but I would be grateful for any other ...
7
votes
1answer
86 views

Mass gap between neutron stars and black holes

From the detection of gravitational waves in GW190814, the merging of a 2.6 solar mass compact object with a heavier object has been inferred. The lighter object is in the "mass gap" between ...
15
votes
1answer
889 views

What would be the maximum stable mass of an artificially created sphere of very cold, very pure hydrogen-1?

The Chandrasekhar limit assumes the white dwarf is made of carbon, but hydrogen has a much lower ratio of mass to electrons, so the limit should be different in that case. And electron degeneracy ...
0
votes
0answers
18 views

Isolated Neutron Stars

What is the difference between isolated neutron stars and neutron stars ? What is the meaning of isolated here ?
0
votes
0answers
7 views

Do the free electrons causing the dispersion in the 'Dispersion Measure' of an FRB refract or re-emit the long-wavelength RF waves?

If the free electrons in the interstellar and intergalactic medium absorb then elastically re-emit the longer-wavelength radio waves coming from an FRB, that would reduce their power, because they are ...
0
votes
0answers
5 views

How to use spectral flux density data while using Planck's law giving spectral radiance?

I'm currently working on a fun project in my free time where I'm trying to calculate the temperature, among other things, of stars based on their spectra. Since I have essentially no prior experience ...
0
votes
0answers
26 views

Why are low-frequency radio transients so rare?

Why are low-frequency radio transient (fast radio bursts, etc) so rare? Is it due to our observational equipment, or something intrinsic to transient phenomena?
0
votes
0answers
27 views

Does Hawking radiation can have any observable effect on Black hole shadow

Last year we captured shadow of black hole at the centre of M87 by Event Horizon telescope. I am wondering if Hawking radiation can have any effect on the black hole shadow. The more I think about ...
0
votes
0answers
12 views

Can I calculate frequency limits using bandwidth and center frequency?

I’m given the centre frequency and bandwidth of a radio transient. I need to determine the frequencies over which the transient occurred. I know there’s a relationship between the two, but I’ve ...
1
vote
1answer
52 views

Formation of Black Hole

Black holes are formed when energy is put in a small region of space, I was wondering if there is a threshold to how much energy should I add in a certain volume of space to get a black hole, I read ...
4
votes
1answer
375 views

How come gravity generates enough pressure to start a fusion reaction in stars even though it is the weakest force?

Given the fact that gravity is the weakest of all forces, how does a gas cloud manage to collapse on itself under gravity and start a fusion reaction, outweighing the electromagnetic and nuclear ...
0
votes
1answer
17 views

Books for Solar physics

I am thinking about applying for an internship at a university under a professor who does Helioseismology. What resources would you recommend me for being ready for such an internship? Can you suggest ...
1
vote
0answers
16 views

Are the LIGO and VIRGO results consistent with the black hole statistics predicted by cosmology?

Have LIGO and VIRGO recorded enough gravity wave events to cross-check the black hole populations predicted by astrophysics and cosmology? Basically, we now have another experimental tool to verify ...
0
votes
0answers
9 views

Which parameters can be used to differentiate between bulge and bulgeless galaxies?

I started doing a project which needs a set of bulgeless galaxies, but I don't how to differentiate between bulge and bulgeless galaxy. It would be useful if you could specify which parameters can be ...
0
votes
0answers
8 views

What is dispersion measure (DM)?

I’m an undergraduate physics student working on a project, part of which involves studying “dispersion measure” (as used in study of pulsars, etc). I think I understand it, but I’m not sure. What is ...
1
vote
1answer
42 views

What would happen to the Sun if you reflect all the light back?

What would happen to the Sun if you reflect all the light back with mirrors?
0
votes
0answers
15 views

Derivation of Press–Schechter mass function for $P(k)\propto k^n$

From 'Galaxy Formation and Evolution' by Mo, van den Bosch and White eq. (7.45) we have that $$ n(M,t)\ dM = \sqrt{\frac{2}{\pi}}\frac{\bar{\rho}}{M^2} \frac{\delta_c}{\sigma}\exp\left(-\frac{\delta_c^...
0
votes
0answers
10 views

Where can I find the specific details of a gravity assist space mission?

I am writing a research essay where I need to know the specific details of a gravity assist mission such as Voyager 2's flyby of Jupiter for example (but any mission would work as long as it is a ...
46
votes
5answers
4k views

What is happening when magnetic field lines snap or break?

In discussions of sun spots and auroras on Earth, magnetic field lines are often described as "snapping" or "breaking", with the result of releasing charged particles very ...
0
votes
0answers
16 views

How strong are the tides raised by Io on Jupiter relative to the ones raised by the Moon on Earth?

There seems to be 2 ways of calculating tidal forces that are contradictory. Either: By calculating the difference of Io's gravitational acceleration on a point on Jupiter's near side and the ...
-2
votes
0answers
28 views

How can one solve the Tolman-Oppenheimer-Volkoff (TOV) equation for $p=p(\rho)$? [closed]

How to solve TOV equation for $p=(\rho)/3$?
0
votes
1answer
29 views

Sachs-Wolfe Effect on power spectrum

From my understanding, there are two main types of Sachs-Wolfe effect: 1)Non-intergrated Sachs-Wolfe effect happens when the photon escapes from a potential well/peak at the last scattering, therefore ...
0
votes
0answers
17 views

Where did the Sun get its angular momentum? [duplicate]

The planets in the solar system all travel around the Sun in the same orbital direction, which is also the direction in which the Sun itself rotates about its axis. Therefore our Solar system has ...
0
votes
0answers
20 views

Question about Matter power spectrum

I'm a bit confused about the statements in the following text: If the autocorrelation function [$\xi$] describes the probability of a galaxy at a distance $r$ from another galaxy, the matter power ...
2
votes
0answers
15 views

Silk damping in CMB power spectrum

Can someone explain Silk-damping in a conceptual way? I understand that it is the effect causing the power spectrum to decrease in amplitude at smaller angular sizes because the effect is apparently ...
0
votes
1answer
33 views

Gravitational force effects on velocities of rotating bodies

If we take a satellite rotating around the earth, then the earth applies centripetal force to the satellite, but what if the satellite suddenly looses kinetic energy, maybe because of collision, the ...
0
votes
1answer
31 views

What is 'parsecs per cubic centimeters' in a radio source's dispersion measure?

The units of 'parsecs per cubic centimeter' is really hurting my brain... Could someone please explain this weird astronomical unit?
1
vote
1answer
36 views

What factors affect the strength of gravitational fields, to what proportion and magnitude?

I have been doing a physics depth study on the topic of "how gravitational waves affect the phase shift of light (in a vacuum)" and have found it difficult to find a source, at least one I ...
0
votes
0answers
7 views

$\text{He II}+\text{free electron}\to\text{He I}+\text{ photon}$ Photon emitted in this process belongs to $\mathrm{He}$ I spectrum or He II spectrum?

I know that He I means the unionized neutral Helium atom $\mathrm{He}$ and He II means the ionized Helium atom $\mathrm{He}^+$. The following table is a spectrum data from NIST (https://physics.nist....
0
votes
1answer
47 views

What causes highly compacted matter to collapse into a black hole? [duplicate]

"The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole". Why does this happen? I mean, why something finite (like the core of a very ...
0
votes
2answers
68 views

Why is dark matter and dark energy needed to explain why there's more and less gravity respectively than there should be? [closed]

Why is dark matter needed to account for that there's more gravity than there should be, and dark energy for that there's less gravity than there should be? Obviously that can't be correct, but I'm ...
0
votes
3answers
74 views

X-ray image of the Earth

Since the Sun emits X-rays, what would happen if we had a hypothetically planet sized x-ray film and exposed it behind the earth? I understand we wouldn't be able to see the insides of the earth, but ...
3
votes
1answer
64 views

(Python) Solving Tolman Oppenheimer Volkoff equations

I'm trying to obtain the Mass-radius diagram of a non-rotating neutron star, following the work of Oppenheimer and Volkoff (I consider an EoS of a free Fermi gas of neutrons) : $$E(x)=\epsilon_0\...
0
votes
1answer
44 views

Is it possible to calculate how much a star's brightness dims when a planet transits in front of it from a viewer's perspective?

Last night I got to thinking about what would happen if Jupiter and Venus suddenly switched places. Since Venus comes the closest to Earth than any other planet and Jupiter is much larger, does that ...
1
vote
2answers
44 views

Number of seemingly brightest stars: minimum around G-stars

This plot gives the amount of the seemingly 10000 brightest stars. Can someone help me to explain why there's a minimum at number 3, I know how to explain 1 (there are less big stars) and 2 (small ...
0
votes
0answers
11 views

Albedo in planets

Let's say we want to calculate the aparent magnitude and temperature of a planet knowing its albedo, radius, and distance to the sun. I do not understand how to use the albedo, would the flux that ...
1
vote
0answers
20 views

When do planets formed via core accretion in a proto-planetary disk stop gaining mass?

I was just trying to go over some of the contents in my exo planets course and wanted to know that if all the planets that form via core accretion continue to attract all the dust in a proto-planetary ...
0
votes
3answers
65 views

Is the yellow Sun light produced by photon scattering inside the Sun?

If the hydrogen emits four distinct light frequencies as a gas and on the Sun surface the gravity cannot alter hydrogen state as a gas does the yellow component of sunlight come from its interior?
0
votes
2answers
60 views

Stellar nucleosynthesis

I would like to learn more about fusion in stars. The question I have is whether there exists a graph showing exactly which elements take part in the reactions. Here, I managed to find some data ...
0
votes
0answers
62 views

Datasets for calculation of exoplanet properties

I would like to create program for calculation exoplanet properties, but I only found transit dataset from Kepler on NASA website. From light curve I can calculate: planet radius $r$ from $\frac{r_{...
0
votes
1answer
35 views

What happens if I place myself on a land pole?

What happens if I place myself in the center of one of the Earth's poles? Could I see how the earth revolves around me?
0
votes
0answers
32 views

Mysterious - different speeds at different latitudes of the Sun

I recently read here (Hyperphysics page on Sun) since the Sun is a gaseous body and hence different latitudes can rotate at varying speeds. Naively, I was guessing that the poles would have faster ...
0
votes
0answers
16 views

Cosmic Microwave background radiation and the spectrum [duplicate]

What does it mean to say that the CMBR has a temerature(~2.7 Kelvins) ?
1
vote
0answers
13 views

Deriving the free streaming distance for HDM particles

I am trying to derive the free-streaming length for the HDM particles but I couldnt follow the arguments given by the article https://arxiv.org/pdf/astro-ph/0201405v1.pdf after equation 83. Thanks
1
vote
0answers
26 views

Formula to get scales of the two components (transverse and perpendicular) of Baryonic Acoustic Oscillations (BAO)

In an astrophysics context about BAO (Baryonic Acoustic Oscillation), it is written on the following paper BAO paper : "BAO are much smaller in amplitude than the CMB acoustic peaks, and are washed ...
0
votes
0answers
10 views

Expansion of the Universe (within galaxies) [duplicate]

We know that the universe is expanding. The galaxies are moving far away from each other. But what is happening inside those galaxies or inside the solar systems? Is our Earth moving further away from ...
0
votes
1answer
26 views

Uncertainty in estimation of mass neutron star

Can somebody explain why there is a large uncertainty in the mass estimation of neutron stars?

1
2 3 4 5
41