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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Startups for astrophysics [duplicate]

Between astrophysics and quantum mechanics both are interesting and I've had an answer for quantum mechanics but is there anywhere I should start at first or any books? I'm 14 so I don't really know ...
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70 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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Dust mass-loss rate from a massive star given a set of parameters?

I've been looking for examples at how mass-loss rates are determined. I'm studying a circumstellar dust shell ejected from a Wolf-Rayet star. I have some parameters like, expansion velocity of the ...
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77 views

Limitations of 2D point-mass Dynamics of the solar system

To model the solar system, I took the planets to be point masses, used newtonian mechanics and modelled the orbits as circular (only Mercury's orbit has appreciable eccentricity). The entire system is ...
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1answer
154 views

How is it possible that Thermosphere can maintain so much heat? [closed]

Thermosphere is the Layer of Atmosphere in approx 100-1000 km altitude. Particles in thermosphere are typically at 1400 K temperature. But the sun activity can raise the temperature up to 2300 K. It'...
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1answer
71 views

How and why do sunspots occur?

I am studying sunspot behavior, and the causes for the occurrence sunspots occur. I've come across the phrase 'local magnetic fields of the Sun'. I have no idea what that means. Can someone please ...
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1answer
116 views

Simple metric of stellar collapse

Is there a simple metric (Lorentzian manifold) known which exhibits the formation of a black hole while not having any white hole counterpart and which moreover satisfies the strong and dominant ...
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38 views

Visible Mass Distribution in a Galaxy [closed]

Is there any known relationship between stellar density and distance from the galactic centre? I want to know how the visible matter is distributed in the galaxy, especially at the bulge.
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52 views

As the World Turns [closed]

Does the Earth's axis change with the magnetic reversal as it is taking place?
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1answer
182 views

What is the largest possible mass for a stable planet made of iron?

Consider a large spherical planet made of pure iron. Think of something similar to Mercury or Earth without its mantle, only much bigger, though those planets have elements other than iron mixed in ...
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616 views

How much faster is the fusion we make on earth compared to the fusion that happens in the sun?

I have come across many websites that states that the proton-proton fusion which is the dominant type of fusion that powers the suns, is extremely slow and that is why the sun is still burning to that ...
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632 views

How do we know that these radio bursts are from billions of light-years away?

NASA just announced that they detected the first radio bursts from outside of our galaxy. Astronomers, including a team member from NASA's Jet Propulsion Laboratory in Pasadena, Calif., have ...
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Lower limits for steady-state black holes

Stellar mass (and larger) black holes emit Hawking radiation below the temperature of the cosmic microwave background; thus, they should always absorb more energy from space than they emit, and always ...
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We say Light is Red-Shifted or Blue-shifted from faraway stars and galaxies [closed]

We say Light is Red-Shifted or Blue-shifted from faraway stars and galaxies. Can we find out the distance at which it changed its frequency. So in another solar system, it might seem to be Green ...
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2answers
101 views

Is sun a black body? [duplicate]

My teacher told me that sun is a black body but after reading at various sites whre they say that sun is not a black body but has black body radiations because it cannot absorb all radiations.
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3answers
125 views

Why are the jets of the “light saber” star slightly curved?

Why don't the jets of the HH-24 object follow a straight line? In the image below, notice how they bend towards left from the expected straight line. Is it an optical distortion, or some nearby ...
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103 views

Dark matter “hair” flowing through the earth

Gary Prézeau of NASA's JPL has done some calculations of how dark matter might be focussed by the Earth's gravitational field (publication preprint), and the results show some remarkable hairy ...
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1answer
41 views

What is the gravitational power that neutrinos created in the big bang exert on us?

I was thinking about the big bang, and I remembered that neutrinos not only travel at the speed of light, but they were also created in massive quantities very early in the universe (Hadron epoch). ...
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39 views

Why is CO a good tracer for H2? How are those molecules correlated?

One always reads and hears that CO is a good tracer for H2. How are they correlated? How can you deduce from the (measurable) CO the amount of the (unmeasurable) H2 in the ISM?
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1answer
64 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
55 views

If there were infinite many stars [duplicate]

If there were infinite many stars, is the sky then always full of light so is there than even night?
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1answer
67 views

Eccentric binary black holes

Comparable-mass binary black hole inspirals and mergers are expected to be an important source of gravitational wave signals for current and future ground-based detectors. It is generally expected ...
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1answer
33 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
40 views

Direction of Gamma Ray Bursts

After a black hole consumes a star, why do gamma ray bursts only shoot out perpendicular to the spinning accretion disk? Why do they not shoot out parallel to the disk?
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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} = \frac{(...
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1answer
266 views

Equation of State and Neutron star

I'm searching for equation of state books, with references to neutron star and ultra-dense matter.
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1answer
303 views

Recommended book for beginners on advanced science topics [duplicate]

I have a background in engineering so I have some familiarity with basic math and science. I've recently been reading about other topics such as Einstein's relativity and have become interested in ...
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1answer
38 views

Black hole corona and bipolar outflows

What are black hole coronas? Are they different from accretion disks? If so, how are they formed?
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255 views

Why do astronomers call all elements heavier than helium “metals”?

I understand that a scientific term need not be constrained by its etymology. But is there some significant reason why astronomers choose to call all elements heavier than helium "metals"? Are ...
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797 views

The final parsec “problem”

Many and perhaps all galaxies seem to contain supermassive black holes of about $10^7 M_\odot$ at their centres. Determining their origins is of great astrophysical interest. In what I understand to ...
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76 views

Here's a fun question, what would happen if Venus was thrown off in a highly elliptical orbit? [closed]

I'd like to know what would happen if Venus was flung into a highly eccentric orbit like Sedna (except maybe with its current perihelion) with an orbital period measured in thousands of years by a ...
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2answers
55 views

Relationships between optical depth, $\tau$, and probability of being scattered

The optical depth is given by many as: $$ \tau=n_e\sigma_{cs}L $$ Where $n_e$ is the number density of the medium, $\sigma_{cs}$ is the scattering cross section and L is the linear extent of the ...
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2answers
593 views

Can we transfer burn to another planet at any time?

Assume delta-v isn't a problem and circular orbits. EDIT: Assume that you're already in orbit so you don't have to shift a massive load of fuel up, and the absolute ideal is something that has a ...
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1answer
67 views

Calculating velocity of a spacecraft between moon and earth [closed]

I'm in high school, I'm not very good at physics, and I have this project (year long). I'm trying to determine the accuracy of a simulator (Universe Sandbox 2) with theoretical velocities vs. the data ...
4
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1answer
156 views

Why do neutron stars have solid crusts?

A long time ago I read that neutron stars have a solid crusts that are several orders of magnitude harder/stronger than alloys here on the Earth. So how is this possible ? A neutron star has a ...
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2answers
107 views

What defines a cold plasma?

Been looking for this very simple answer for a while now, and google returns a face cream with the words cold plasma in it. Very frustrated. Just wondering, what constitutes a cold plasma in the ...
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130 views

Good books or resources for Stellar Astrophysics at graduate level?

I wanted to know if there is a well established resource in the field of Stellar Astrophysics which is not very outdated. I have seen plenty of books at my university library but I do not know if ...
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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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Astrophysics of spirals [duplicate]

What accounts for the structure of spiral galaxies? I would seem that, considering gravity is proportional to distance, outer objects could not be connected in any way to inner objects (ie. a spiral) ...
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2answers
54 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
59 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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44 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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1answer
96 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 source....
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1answer
253 views

Are ultracold atoms only created by intelligent life?

Nature has particle accelerators that are far beyond our capacity, but occasionally I hear atomic physicists claim that they are able to make something that has never been formed in any natural ...
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1answer
103 views

What is the process that causes a collapsing star to bounce back? [duplicate]

Can someone explain the process by where a star collapses and bounces back. I haven't been able to find a good explanation of the bounce. Edit here, I was wondering specifically where the energy of ...
4
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2answers
577 views

Accuracy and assumptions in deriving the Tully-Fisher relation

I understand the mathematical derivation of the Tully Fisher relation from basic physics formulas, as shown on this site. However, after using the physics equations, it seems that several assumptions ...
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4answers
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Are neutrino stars theoretically possible?

Since neutrinos have a small mass and are affected by gravity, wouldn't it be theoretically possible to have such a large quantity of them so close to each other, that they would form a kind of a ...
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4answers
131 views

What could break up a neutron star?

Beside the obvious answer black hole, is there anything else? Could a nearby supernova blow it away/apart? Or any sort of (theoretically intense enough) field? I guess an electric field is out of the ...
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1answer
57 views

What percentage of the energy in a dust cloud must be lost before it can collapse into a star?

With reference to this previous question about how dust clouds can collapse to form stars: How is hydrostatic pressure overcome when a star is formed? The answer given is that they must radiate away ...