The Stack Overflow podcast is back! Listen to an interview with our new CEO.

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
0
votes
0answers
25 views

How much $^{56}Ni$ is needed to power a supernova of $10^{44}J$ energy? [on hold]

Folks, Apologies for this question, A supernova has a KE of 10^30 J and it is powered entirely from 56Ni decay. How much 56Ni is needed? I was looking for pointers in what formula is us or how to ...
0
votes
0answers
12 views

Query concerning black holes [duplicate]

What information can be conveyed from a black hole about the substances and radiations it absorbs into it's singularity.
9
votes
3answers
1k views

Is dark matter inside galaxies different from dark matter in intergalactic space?

I just read a text about astronomy and when talking about dark matter the author says: [...], the dark matter responsible for the orbits of the stars in the Milky Way is probably different from the ...
0
votes
0answers
23 views

Limit of energy? [on hold]

What if there is any real limit of energy that can ever be accumulated in the gravitational field? Described as: E(max) = m(max) * c^2 So... If some black hole reached that limit, (I would expect) ...
4
votes
2answers
219 views
+100

Why does this simple equation predict the Venus surface temperature so accurately?

Assume the atmosphere of Venus behaves much the same as Earth. However, it is closer to the sun, has a thicker atmosphere, and is less massive. Further assume: The insolation should follow the ...
2
votes
0answers
17 views

Could Breakthrough Starshot spacecraft detect hypothetical Planet Nine?

Since we just want to prove if Planet Nine exists in our solar system and know the approximate position of the planet if it exists, we can avoid most of the technical challenges for StarChip (camera ...
1
vote
0answers
30 views

Theoretically, Is it possible to create a nova by firing large masses into a sun?

In a science fiction story (Bobiverse) a nova is created by accelerating two small planets at relativistic speeds into a sun from opposite sides.The shockwave creates hydrogen fusion on opposite sides ...
0
votes
0answers
17 views

A Belinski-Khalatnikov-Lifshitz (BKL) singularity

In general, if the perturbed Friedman model behaved according to the second law, Sir Penrose speculated that numerous black holes would merge and collapse, resulting in one final singularity - Very ...
0
votes
1answer
21 views

Solar astrophysics--flux derivation [duplicate]

The question reads: The solution reads: My only answer is for 4 and it is $\pi I_\nu$. Where did I go wrong?
2
votes
2answers
523 views

What would Happen if a Primordial Black Hole, with 5-10x time the mass of Earth, were to fall into our Sun?

So lately i heard of this theory that planet 9 might be a Primordial Black Hole (PBH) with 5 - 10 times the mass of Earth. I was thinking to myself, what would happen, if such a PBH (if it even exists)...
1
vote
0answers
26 views

Why dont radio waves diffract through radio telescopes instead of being reflected? [duplicate]

If you take this picture of a telescope It has several gaps through it. My lecturer was mentioning how as long as the holes and imperfections in your disk are less than the wavelength of light you ...
5
votes
1answer
552 views

Could Alpha Centauri be made of anti-matter? [duplicate]

How can we tell if a star is made of matter or anti-matter? For example, is there any difference spectroscopically? Or could we tell from cosmic rays? If half of the stars were made of matter and ...
0
votes
0answers
14 views

Would GEODEs explain late Saggitarius A* Flashes?

I read recently about the sudden brightness near the black hole Saggitarius A*. One of the proposed explanations is that a known cloud of gas passing nearby sometime recently took longer to arrive ...
0
votes
2answers
54 views

Why do Type II supernova happen? [duplicate]

I am an engineer and not a physicist. I am unable to understand why SuperNova happen. I understand that when the core is composed of high atomic number of elements like Iron and further fusion is not ...
0
votes
1answer
45 views

Photon near a black hole - find distance of closest approach from impact parameter

I have the equation relating the impact parameter $b$ to the distance of closest approach $R$. $R^3 - b^2R + 1 = 0$ which can be solved in python. I have a given $b$ and have to find $R$. however, ...
0
votes
1answer
30 views

Looking for a good book on star stability

Can anyone recommend me any resources from which I could learn about how stars maintain a stable form, maybe using some thermal and nuclear physics, and maybe fluid dynamics, but not so advanced. ...
1
vote
0answers
35 views

Is there proof that pulsars beam like a lighthouse?

Shortly after pulsars were discovered in the late 1960s, Scientific American had an article about the new discovery. I believe the author of the article was not sure whether pulsars were beaming ...
-3
votes
2answers
92 views

Supernovas create energy?

Ok here we go. Supernovas do have to have energy spent to explode, that is known. That explosion power also equals to the energy spent to cause said explosion, this is also known . Besides creating ...
0
votes
1answer
68 views

A thought experiment related to the age of the universe

Okay, So, this thought experiment starts with the movie, Interstellar. In which humans went through a wormhole to a system consisting of a Black Hole. They landed on a planet (I don't remember its ...
0
votes
0answers
30 views

AGN accretion disk double peak explained?

I have a question to the following lecture: https://ned.ipac.caltech.edu/level5/Fabian4/Fab2_2.html In Figure 3 it says that a narrow annuli of a Newtonian disk should alrdy show a double peak ...
2
votes
1answer
33 views

Effective potential for Kerr geometry

In the review Foundations of Black Hole Accretion Disk Theory, the authors defines an effective potential for Kerr geometry as (Chap. 2, eqn. 23) $$\mathcal{U}_{eff}=-\frac{1}{2}\ln\left|g^{tt}-2lg^{t\...
1
vote
2answers
82 views

Are neutron star cores thought to be stiffer than photon gases?

The weak energy condition and with the dominant energy condition allow anything from w=-1 to 1 (meaning that the magnitude of the pressure can be at most equal to the total mass-energy density). ...
4
votes
1answer
80 views

Terminology used in the Wikipedia article for wormholes

The lead section of the Wikipedia article for wormholes says the following: More precisely it [a wormhole] is a transcendental bijection of the spacetime continuum, an asymptotic projection of ...
2
votes
3answers
61 views

Energy from fusion beyond iron peak

In the diagram of nuclear binding energy per nucleon Eb/A (vertical axis) and mass number A (horizontal axis), Fe-56 has one of the highest values. Many authors state that nuclear fusion can only ...
3
votes
1answer
39 views

Does the curvature of light around a “centre star” in gravitational lensing affect the age at which we view the object being “lensed”

It occurred to me that during gravitational lensing, the light curves around a given object, creating a curved path. Because the path of light is curved, and thus, longer than a straight path, would ...
0
votes
0answers
16 views

Dispersion: any software to work out the dispersed waveforms of EMW signals that propagate via interstellar medium for some distance?

I asked this question in the Astronomy site, but seems few people feel interested in, so I hope to have a try here in the Physics site...... Is there any software (toolbox, code, package, paid or ...
1
vote
1answer
35 views

Is there a Mass-Temperature relationship for main sequence stars?

When finding relationships between various properties of stars, I frequently find next to nothing on the Mass-Temperature relationship. I, of course, see the Mass-Luminosity and the Luminosity-...
0
votes
1answer
49 views

In Kepler's third law, why isn't k somehow proportional to the planet's mass?

Given Kepler's third law: $\frac{T^2}{D^3} = \frac{4\pi^2}{G(M+m)} = k$ I'd expect that, the larger a planet's mass (m), the smaller it's constant (k). However, that's not what I've seen in ...
0
votes
0answers
25 views

Newtonian/Relativistic Solutions of Fluid Disks in orbit around a massive body

I have been trying to make an RMHD (Relativistic Magneto-Hydro Dynamics) Set-up of a Disk around a Massive Rotational Body. The initial paper I have been studing a paper which uses a Fishbone & ...
0
votes
0answers
35 views

Derivation of radial momentum equation in Kerr geometry

I am trying to derive the radial momentum equation in the equatorial plane of Kerr geometry obtained by Lasota (1994) which reads (eqn. 6 in page-343; I am using units in which $M=1$) as follows: $$uu'...
0
votes
2answers
58 views

What conditions provide the oldest star?

If we define the start of the lifetime the protostar and the end of the lifetime a red giant (at max volume), what conditions would make this time the longest when the star was first formed and ...
1
vote
0answers
29 views

Question on Jupiter's Core

A paper published by UC Berkley in 2010 (article about it here: https://www.sciencemag.org/news/2011/12/jupiter-eating-its-own-heart) tested what happens when magnesium oxide (one of the constituents ...
1
vote
1answer
58 views

Black hole spin measurements

While measurements of black hole spin of supermassive black holes in AGN using the X-ray reflection method (as shown in the figure below), 90% confidence error bars on black hole spin and 1$\sigma$ ...
3
votes
3answers
123 views

Why are primordial black holes considered non-baryonic? [duplicate]

A very important question that has been bugging me is why do people consider primordial black holes to be non-baryonic. I know that such a statement is then used to saying that they can be considered ...
1
vote
1answer
46 views

Correct my view of energy levels in universe?

Kindly apologize me if I am sounding very naive and wrong. I am very new to the field of solid state physics. I am having this question in my mind. We know that a solid has energy levels for electrons ...
1
vote
2answers
67 views

How does a quasar convert mass to energy?

I'm trying to understand where the energy for a quasar comes from and specifically if it comes from converting mass to energy. I know that as matter falls into a black hole gravitational energy is ...
0
votes
0answers
62 views

M3 globular cluster: simple age determination

For my pre-university pupils I would like to find a simple way to determine the age of the globular cluster M3 using a colour-magnitude diagram (CMD, B-V horizontal axis and apparent visual magnitude ...
5
votes
1answer
211 views

What fuel is J005311 burning?

J005311 is two white dwarf stars that have merged in such a way, that, well they merged instead of exploding. (Only 7 or so such mergers have been found.) Its stellar wind is blowing at 16,000 km ...
15
votes
1answer
1k views

How do neutron star binaries form?

Do neutron star binary systems come from previously active-star binaries, where where both stars have gone supernova and left behind neutron stars that are still in orbit? Or do they form when two ...
1
vote
4answers
128 views

If our solar system was filled with air instead of the vacuum, would earth be colder or hotter?

Would the heat from the sun be transferred better to earth, since air is an isolator inferior to vacuum thus producing a hotter environment? Or would the energy be absorbed and dissipated in the air,...
2
votes
1answer
78 views

Interpretation of 21 cm intensity mapping

I'm currently trying to understand the following plot from Astrophysics for physicists by A.R. Choudhuri. I think I understand the basic concept of measuring the line-of-sight velocities with the ...
1
vote
2answers
110 views

Why is the spectrum of a star pretty much continuous? [duplicate]

I was reading about the development of the quantum theory when I got to the explanation for spectral lines. It's a topic that I've revisited many times but I came up with a question. I know that in ...
1
vote
1answer
40 views

Positron beta decay in stellar core plasma

According to introduction level textbooks $\beta^+$ decay, that is conversion of protons into neutrons only occurs in atomic nuclei. $$p \xrightarrow{\beta^+} n + e^+ + \nu_e$$ I understand that it ...
0
votes
1answer
33 views

Fluidity Threshold

How was the fluidity threshold for giant (liquid) planets of 60 E24 kilos (about 10-15 Earth masses), which corresponds to some 30,000-40,000 km. diam., arrived at? Buchave et al (2014), of the ...
1
vote
0answers
17 views

What are Quasi-Periodic Oscilations and how can they be used to determine the mass of black holes?

Quasi-Periodic Oscillations (QPOs) are observed in almost all accreting systems and they provide an essential tool to explore accretion flows from compact objects. But I couldn't understand what ...
2
votes
1answer
50 views

Will pyrolytic carbon/graphite repel the Sun's solar wind?

Since a moving charged particle has a magnetic field, as well as an electric field, and pyrolytic carbon/graphite repels an external magnetic field, would this mean that an object made out of ...
1
vote
1answer
43 views

Intensity mapping of the 21 cm line

I'm currently reading Astrophysics for physicists by A.R. Choudhuri. Section 6.5 of his book he presents the following plot: and tries to explain how it was generated. I'm having a hard time ...
7
votes
3answers
933 views

When we are talking about black hole evaporation - what exactly happens?

According to Wikipedia: Hawking radiation reduces the mass and energy of black holes and is therefore also known as black hole evaporation. Because of this, black holes that do not gain mass ...
0
votes
1answer
28 views

Does the direction of Earth's axial tilt change over time? In relation to the sun? What about the 'pointy ends' of our ellipse?

Does the direction we are tilted change in relation to the background stars? And the points where our ellipse is pointiest? (most elongated?) Does this change the timing of our aphelion and ...
0
votes
0answers
35 views

Stellar Aberration

In Stellar Aberration Experiment how do I know there is a star above my head before doing the experiment? Reference: Special Theory of Relativity - Resnick (Section-1.7)