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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squeezed radiation astronomy

Squeezed electromagnetic vacuum does have a renormalized energy density smaller than the vacuum. So it makes it in my opinion a inconspicuous candidate for a dark energy carrier. Are there ...
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48 views

Experimental tests of Cluster Decmposition

How tight are experimental and astrophysical tests on whether Cluster Decomposition is satisfied at various space-like separations? Is there a review paper or a standard reference on the question? I ...
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2answers
132 views

Why are galactic centers always brighter than the edges?

As you can see the image below and other galaxy images, the center is generally much brighter. Why is that? Is there a very big star? A very big gravitational field?
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1answer
217 views

models for astrophysical relativistic jets from compact objects

what is the simplest way to understand the physics of relativistic jets? we know that they have axial symmetry with very tight angular spread, presumably aligned with the axis of rotation of the ...
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60 views

How is the universe expanding? [duplicate]

Possible Duplicate: spacetime expansion and universe expansion? Is the space between planets is growing or the space between stars is growing or the space between galaxies is growing?
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1answer
6k views

Negative and positive energy and Hawking [closed]

I don't have any physics background (except the material we did in high school-long time ago). I was watching a documentary with Stephen Hawking about whether God created the Universe and I could not ...
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2answers
114 views

Precessional motion of active galactic nuclei

I want to set a simulation for jet which has a precessional motion. The symmetry axis of jet is $z$ axis, i.e. jet is propagating along $z$ direction making angle $\theta$. I set the velocity ...
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1answer
130 views

Does diffraction contribute to the Black Drop effect?

Two reasons are given to explain the black drop effect here, but I think I came up with a third. Consider a two-dimensional cross section of the situation just after second contact and just before ...
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2answers
155 views

Radiative transfer equation solution

The solution of the radiative transfer equation for spherical ionized blob : \begin{equation} \frac{dI_{\nu}}{ds} = j_{\nu}-\alpha I_{\nu} \end{equation} and solution is (Ref: ...
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1answer
1k views

Do materials cool down in the vacuum of space?

Do materials cool down in the vacuum of space? If yes, how does it really work?
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2answers
250 views

Pressures Necessary for Carbon Detonation

Carbon detonation is a characteristic event of Type 1a Supernova (EDIT: where an accreting white dwarf near the Chandrashankar limit of 1.4 solar masses explodes), an extremely important standard ...
0
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1answer
98 views

Is there any way to produce food without sun, synthetically?

Is there any way to produce food without sun, synthetically? I mean if we face solar winter. look at: Is there any way to survive solarwinter like in Sunshine - movie?
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1answer
629 views

Analogy between magnetic bottle and Van Allen's radiation belt

A magnetic bottle is an arrangement that permits to confine charged particles. Here you can find a review for charged particle rotating in a magnetic field and at the bottom of the page a description ...
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2answers
118 views

Is there any way to survive solarwinter like in Sunshine - movie?

Is there any way to survive solarwinter like in Sunshine - movie? Solar winter is where for some reason sun looses its capasity to produce radiation( heat etc.). It doesn't loose everything but some ...
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2answers
90 views

Regarding binary systems (with pulsars)

Are binary systems (in case of stars and other celestial bodies) more favorable than independent existence? I've been going through an article regarding pulsars, where it was stated that 'many pulsars ...
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3answers
239 views

How many stars within 5 parsecs?

I've ran some scripts on some star catalogs, which counted the number of stars with a parallax greater than 200 mas, which should mean everything closer than 5 pc. The results are as follows: ...
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2answers
51 views

Locating a Comet, how is it done?

How are the comet-hunters able to precisely locate/know about the required comets ? How can they distinguish between comets from such a far distance ? How are they able to estimate the exact time ...
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2answers
1k views

Parabolic or Hyperbolic?

How can astronomers find the difference between a parabolic and a hyperbolic comet ? What are the criteria that helps them distinguish these ? Can a parabolic comet switch over to become a hyperbolic ...
0
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0answers
26 views

Expansion of Universe [duplicate]

Possible Duplicate: Why space expansion affects matter? If the Expansion is prevalent, i.e. it is observable and true then shouldn't that result in the expansion of the Milky Way galaxy, ...
0
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1answer
88 views

Gravity and Magnetism on Stars

I am familiar with the fact that Magnetars have a really strong magnetic field and an ordinary star such as the Sun has a very strong gravitational field. But what about the opposite? What is the ...
2
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1answer
228 views

When would the proposed black hole at the centre of Milky Way gulp in our solar system? [duplicate]

I've heard and read that our solar system lies near to the peripheral region of the Galaxy. Then accordingly we would have a greater probability of sustaining to eventual gulping down by the ...
2
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1answer
590 views

Combined Gravitational Force Vectors in a Spherical Coordinate System

Asking a question here is quite intimidating for me -- while I love Physics, my high-school understanding only allows me to go so far... I've been trying to solve this problem for the last couple of ...
3
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1answer
603 views

Why will the increase in the sun's luminosity accelerate with respect to time?

From http://en.wikipedia.org/wiki/Future_of_the_Earth#Solar_evolution At present, nearly half the hydrogen at the core has been consumed, with the remainder of the atoms consisting primarily of ...
0
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1answer
154 views

Is it possible to mould _ruptures_ in Space-time?

In one of the documentaries hosted by Morgan Freeman, a reference was made that just like an ordinary three-dimensional object like a ruler has scratches and cracks, in the same way there might be ...
2
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1answer
241 views

How early can scientists detect that a deadly asteroid will hit planet earth?

With the advancements in science and technology, how early can scientists of the world detect that a certain asteroid will hit planet earth and cause damage? Are there any impact avoidance strategies ...
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1answer
471 views

How does a star wobble due to orbiting bodies

What equations determine how a star wobbles in response to an orbiting planet, and can it be used to determine the mass of distant objects based on the wobble? If there are other more reliable ...
2
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1answer
112 views

Black Holes, New Branes and Stars

Could a dying star in one brane ( assuming that we live in a world of multiple branes { not a Randal-Sumdrum model of a single brane}) be the start of the birth of the star ( more precisely Super ...
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1answer
151 views

Proportion of energy compared to mass in universe

In Wikipedia (http://en.wikipedia.org/wiki/Dark_matter), there is a picture that shows us the proportion of matter and energy in the current universe - CMB. It seems to suggest there is nothing that ...
2
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1answer
173 views

Earth's magnetic field, could the poles be reversing?

Lately, I've been 'monitoring', if you will, the earths magnetic field, i've come across some strange looking activity periodically. I exchanged some emails with a guy from NASA today, Joseph Gurman, ...
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2answers
487 views

Calculating eccentricity from semi-major axis, position and velocity of particles

I'm trying to calculate the eccentricity of a binary system's body knowing the bodies' velocities, positions, masses and the semi-major axis. I am only trying to calculate the eccentricity for one of ...
3
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1answer
102 views

missing dark matter?

A recent arXiv article measures the variation of gravitational potential in a local region around the solar system, and from that it tries to infer the mass density. Are there any valid ...
6
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2answers
2k views

Do the stars imaged by a telescope even exist at present?

I know that we now have telescopes which can capture the images of the stars and galaxies millions of light-years away from us. Does the telescope capture the past image of the star, i.e. the light ...
6
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1answer
326 views

Why do the stars in the galaxy core move so fast?

There are a bunch of stars orbiting the black hole in the center of our galaxy. These stars move at huge speed. Why do we see this? Why do the black hole not impose any noticeable time dilation on ...
3
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1answer
128 views

What are some ways that humans could have influence over what sequence a star was in?

How would a society go about either preventing our sun in its primary sequence from going into a Red Giant a billion years from now? Or perhaps, accelerating the process of going from main sequence ...
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1answer
177 views

What is solar storm?

I have tried to search through the internet about the definition of solar storm or what this term mean but i could found what it means. Also, what is the difference between the geomagnetic storm
6
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1answer
142 views

What prevents stars in globular clusters from merging over time to form a black hole?

Globular clusters are apparently very very old, and the density of these clusters appears to increase as one approaches the center of a cluster. Orbits are bound to be chaotic, since there is no ...
4
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1answer
191 views

Simulating a black hole binary system

As part of a project for my degree I am writing code to simulate N-body gravitational interactions, however I have to then use this code to investigate something. Struggling to think of ideas I ...
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3answers
462 views

Shouldn't stars disappear from our view due to expansion?

The currently accepted theory of the expansion of the universe would suggest that for any point in the universe, there is a 'boundary' (somewhat like the Schwarzschild radius) beyond which it cannot ...
5
votes
4answers
914 views

Why doesn't the Earth leave you as soon as you escape it?

I've always wondered, that since the Earth is moving at a very fast velocity around the Sun, why is it that when astronauts leave the Earth, the Earth doesn't immediately move away from them at ...
8
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4answers
697 views

Do neutron stars reflect light?

The setup is very simple: you have a regular ($1.35$ to $2$ solar masses) evolved neutron star, and you shine plane electromagnetic waves on it with given $\lambda$. Very roughly, what shall be the ...
11
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1answer
2k views

What will happen if a gamma-ray burst hits the Earth?

Is there any probability that a gamma-ray burst (GRB) could affect the Earth?
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1answer
970 views

Shouldn't the fourth dimension be energy/mass, and not time? [closed]

First of all, I am in 8th grade. That doesn't mean you have to make your answer simple and easy to understand, but I ask you not to be too critical of my query/theory, because I don't consider myself ...
6
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2answers
195 views

Io - Turned inside out

In a lot of the descriptions of the moon Io it frequently states that the moon, because of volcanic activity, has been literally "Turned inside out". What exactly is meant by "Turned inside out" and ...
4
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1answer
421 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 ...
2
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1answer
264 views

Function to determine Earth-Moon distance vs. time

I had no luck trying to find a function that determines the distance between Earth and Moon versus time. (Moon ground level to Earth sea level) Accuracy: the acceptable time range would be for ...
5
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2answers
351 views

How is it that some nebulae are rotating and others are not?

First, I should make it clear that this isn't a question about angular momentum (unless I may have completely missed something). It is my understanding that a nebula must have some inherent initial ...
6
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1answer
156 views

Frequency of nomad planets passing within 30 AU of the sun

A recent estimate by the Kavli Institute for Particle Astrophysics and Cosmology (a joint institute of Stanford and SLAC) is that there are circa 100000 times as many 'nomad planets' as stars I ...
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1answer
178 views

From Computational Astrophysics to Finance [closed]

If for some reason, an Astrophysics graduate decides to shift to Finance will he/she be in a better position (given his/her overspecialization) to make a transition compared to his/her counterparts ...
3
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2answers
106 views

Cosmic radiation cutoff at LOW energies?

The energy spectrum of the cosmic radiation (not CMB) is limited to both sides. I know about the GZK-cutoff at high energies. Basically the interaction probability for photons of energies above 10^20 ...
6
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0answers
57 views

Status of large-scale structure formation within cosmology today

Since the CMB results of the past decade, would it be fair to say that the consensus among cosmologists is that cosmic strings are no longer considered as a (major) source for density perturbations? ...