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.

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Is there a doppler effect on the images of stars around rotating black holes?

I'm an illustrator working on a project involving rotating black holes like those discussed in "Gravitational Lensing by Spinning Black Holes in Astrophysics, and in the Movie Interstellar" by James, ...
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95 views

What causes the death of the Sun?

In a previous question I learned that in each second only a miniscule portion of the total hydrogen in the Sun is converted to helium and that the number is 1/10^18 of its mass converted each second. ...
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45 views

Sound speed vs Speed of sound

Are 'sound speed' and 'speed of sound' the same thing? If not, what is the difference? If they are, could you clarify how the speed of sound applies in the below description of gaseous clouds? ...
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1answer
742 views

Do intergalactic magnetic fields imply an Open Universe?

According to a paper on the arXiv (now published in Phys Rev D), they do. How credible is this result? The abstract says: The detection of magnetic fields at high redshifts, and in empty ...
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261 views

Metal-rich star formation

While discussing star formation on cosmological scales with some classmates, we mentioned the breakdown between the different stellar populations via metallicity: Population III: $Z = [{\rm Fe/H}] ...
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1answer
63 views

How does Planet 9's perihelion and aphelion affect the Kuiper belt objects?

Assuming that the existence of Planet 9 is confirmed and it really exists, how does it affect the orbits of the Kuiper belt objects? My understanding is that the discovery came in part from the ...
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1answer
278 views

Gamow peak and nuclear reaction rate

It's known that the nuclear reaction rate (inside a Star) can be determined with $$R_{ab}=n_a n_b\left<\sigma v\right> \, \approx \, n_a n_b \Big(\frac{8}{\pi m_e}\Big)^{1/2} ...
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68 views

What is the average temperature of mass in the universe?

That is, ignoring speculative concepts like Dark Matter and just summing across stars and gas clouds etc
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28 views

Where can I find accesible educational material on the formation of the solar system?

I'm kind of scathing my head over this. First of all, I'm not a physicist of any kind, I'm a software developer, but I'm also a bit passionate about astronomy(usually read the news) and in my free ...
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1answer
32 views

Regarding the mass of the core of the star

I was reading up about the Chandrashekhar and Oppenheimer Limits when I came across a problem, where the mass of the star could be estimated. My question then is, how can one calculate or estimate the ...
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1answer
50 views

Is the fluctuation pattern of the Cosmic Microwave Background (CMB) identical in every location of the universe?

I know that the Cosmic Microwave Background (CMB) is the leftover radiation from the "surface of last scattering". Let's say an alien civilisation lives on andromeda or further away. Would they see ...
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1answer
69 views

Pluto's internal heat source

When the first images were announced from the New Horizons probe back in July, there was a lot of fanfare about how the surface is young and geologically active, thus requiring an internal heat ...
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1answer
38 views

Origin of Stellar Nurseries

What is the mechanism thought to cause huge stellar nurseries to form e.g. eagle nebula?
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1answer
38 views

Short Gamma Ray Bursts from black hole mergers

I have read in passing that short gamma ray bursts can be caused by the merger of 2 black holes in a binary system. I have Googled but can't seem to find any good sources describing the phenomenon ...
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1answer
34 views

Is there any evidence from observational cosmology to say Dark Energy dominated era begins 5 billion years ago

People say that Dark Energy Dominated era begin 5 billion years ago. Do we have evidence for that from observations
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1answer
128 views

Crab pulsar radiation

Regarding the radiation from the Crab pulsar and nebula, some reading leads me to the following conclusions. The rotation energy of the neutron star is the source of the non-thermal electromagnetic ...
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1answer
91 views

Type II supernovae explosions

I'm quite confused about the explosion of a Type II supernova. As far as I understand, when the Fe-56 core has been created, and the star has all the other layers around it, it starts to collapse, ...
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1answer
61 views

How do fluids behave in space?

In outer space under absence of any external force (like gravity) can a free liquid develop pressure due to cohesive forces? Will the liquid be in spherical shape and will pressure increase towards ...
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1answer
25 views

Help reading power spectrum graphs?

How would I go about figuring out how long a source was measured when given a graph of the power spectrum? From notes I'm following, they just state the total observation time as being roughly ...
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1answer
67 views

What does multi-periodicity mean in stellar pulsations?

How can there exist multi-periodicity in stellar pulsations? http://www.kitp.ucsb.edu/sites/default/files/kitp/preprints/moskalik2.pdf How can one visualize a multi-periodic pulsation or oscillation?
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1answer
51 views

Are the large moons of Jupiter, Saturn, and Neptune still cooling and does this give and indication of their age?

The core temperatures and the rate at which they emanate heat should correspond to their estimated age. Other forces may create some heat such as the tidal locking that is supposed to be the source of ...
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62 views

In what ways does the sun output energy?

I'm curious about the energy output of the sun, and how it breaks down. What fraction is from EM radiation, solar wind, neutrinos, et cetera? How does energy output vary over the EM spectrum? I was ...
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117 views

Modelling a matter dominated universe collapsing into a black hole

With the FLRW equations we can get solutions for a matter dominated closed universe in which the finale is an ultimate collapse, but this is only in terms of $a$ (the scale factor) and $t$ (time) and ...
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78 views

Do wormholes have a side to their path through space?

In theory do wormholes have a side to their path through space? What is there at a point in line with the entry and exit, would anything look different at that point in space? Could a space ant get ...
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798 views

Map of the gravitational strength of the solar system

I am looking for a map or plot of the gravitational strength in the solar system. In an ideal world there should be something like google earth to move around in the solar system, zoom in and out and ...
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32 views

Could a satelite be pulled away by gravity while the object it was orbiting keeps unaffected in its own orbit?

I'm asking this, since I try to educate my self a bit in the field of astrophysics. From my point of knowledge the by title given scenario could occur. But I haven't yet read anything that sounded ...
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38 views

How are planets distributed in elliptical galaxies?

I'm trying to figure out if planets are equally distributed in galaxies (I'm assuming they aren't) or if there is some logic behind their distribution.
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49 views

Does a planet's orbital angular momentum affect its rotational angular momentum?

For example: If the moon was closer to the earth, assuming the orbital momentum was conserved and not worrying about earth's rotation, would the moon's rotation rate be effected?
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16 views

Origin of the minimum speed formula for relativistic jets

I am studying superluminal motion in relativistic jets. I understand that the velocity of an emitting part of the jet $v$ can be related to the transverse velocity $v_t$ via $$ \frac{v}{c} = ...
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27 views

Direct vs indirect detection of dark matter

Background There are two categories of searches for dark matter. Direct Detection via reproducible experiments Indirect detection Detection of e.g. annihilation signal from astrophysical sources ...
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21 views

What is Colour-Colour-Intensity Diagram?

What are color-color intensity diagrams? These are 3D plots usually used in high energy astrophysics ( particularly in relation to XRBs).
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32 views

How far inside a white dwarf Roche limit does the Earth have to be to start losing large chunks of rocks?

I have calculated that for a one solar mass white dwarf orbited by the Earth, the Roche limit is about 600,000 kilometers. I understand that any loose mass on the surface of the Earth would start ...
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35 views

What is the physical meaning of source function in radiative transfer?

I know that it's the ratio between emission and absorption coefficients.But what does it actually mean? Can you please explain?
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22 views

Do the arms of spiral galaxies differ based on the speed of which the galaxy is rotating?

If I were to take a circle with strings attached to it and spin it, the strings would behave differently based on how fast the circle is rotating. Do galaxies behave the same way?
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9 views

Region of resonance and overlap

In planetary dynamics what does a region of resonance (mean motion) between two bodies mean and how to quantify the region? How does resonance overlap occur and what are its consequences? What is ...
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54 views

Synchrotron radiation derivation

In the derivation of synchrotron radiation in a standard text (J.D. Jackson/Rybicki & Lightman), we do it by taking instantaneous circular motion of the electron, because the power emitted by ...
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29 views

In a supergiant star, is the energy transport inside the star mostly convective or radiative?

I know this has to do with the super-adiabatic and adiabatic characteristics in stars, but I'm unfamiliar with them. I'd love some discussion on this topic. Additionally, what determines the ...
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42 views

Perturbations of planetary Orbits

I have, for years, been an Astronomy and physics nerd. For the first while, I was a total astronomy nerd. Then I slowly transitioned into physics and have been, for less than a year, a physics nerd. ...
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40 views

Density of an astrophysical ring of fluid around a star

*An equilibrium ring of isothermal fluid orbits a star at radius R. In the plane of the ring, mechanical equilibrium results from a balance of centrifugal force and the gravitational force of the ...
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0answers
27 views

How much cheaper and smaller on average is SiPM technology over conventional PMTs?

I've heard it said that some of the major advantages of silicon photomultipliers are its low cost and compactness when compared to widely used photomultiplier tubes, but haven't found much information ...
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52 views

Graviational Lensing Data

Can anyone provide me with (or point me to) real life gravitational lensing data that I can plug in to the first equation on this page (the standard lensing equation): ...
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0answers
38 views

Resources on Solar Neutrino Physics

For a project I'm doing for an introductory Astrophysics course, I'm trying to understand the nuances of solar neutrino physics. However, most of what is said while explaining neutrino oscillations ...
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56 views

Does the zero energy universe hold true on some mathematical grounds besides observations?

I was reading Stephen Hawking's 'The theory of everything' when I came across a very interesting type of universe, the 'zero energy universe' since then, I've read some websites but all they used to ...
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67 views

Why are other universes in the picture of Dark Flow?

It seems to me that the popular suggestive explanation of dark flow is another universe interacting with ours. Isn't there other alternative explanations?
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57 views

What's the shocks mach number in this specific problem?

The shock wave I'm interested in occurs for a special Riemann problem, known as 1D Noh's problem. It means basically that two streams of air (equal density) are colliding at $x = 0$ for $t = 0$; I ...
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277 views

How fast do large asteroids usually travel?

I have just watched this video made by discovery channel, and you can hear the narrator at 0:51 saying that : "even though it is moving at 720 THOUSANDS kilometers per hour..." I stopped once I heard ...
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51 views

Mass of dark matter

The Alcubierre warp equation specifies that negative mass is required for said "warp drive" to function properly. Could dark matter provide the negative mass that's required?
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30 views

Redshift Dependence in the Spatial Orientation of SDSS Galaxies having Redshift 0.19 to 0.20

Does redshift depend on the spatial orientation of SDSS galaxies with redshift in the range 0.19 to 0.20 ?
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143 views

Relation between the period of rotation and the period of revolution of a satellite

I read somewhere that the tidal forces between the earth and the moon causes the equality between the 2 periods of the moon and that every planet-satellite system will evolve to this condition (like ...
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112 views

Mass loss rate of planetary nebulae

The “interacting wind” model of planetary nebulae is based on the idea that the white dwarf phase of stellar evolution is preceded by a red giant phase. A fast wind from the hot white dwarf overtakes ...