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.
8
votes
1answer
55 views
Voyager 1 cosmic ray strips
In the last months Voyager 1 has experienced a dramatic drop in the cosmic ray radiation, which was been exceptionally uniform for the last 10 years, except for the past july 28 and august 14 events, ...
0
votes
1answer
105 views
Do all black holes spin in the same direction?
My question is as stated above, do all black holes spin the same direction?
To my knowledge, the spin in the direction of the spin of the matter that created them. Another similar question was asked ...
7
votes
0answers
86 views
gauss-bonnet gravity constraints from string theory
recently there has been advances in observational constraints of gravity theories that contains scalars coupled to the gauss-bonnet topological term:
http://arxiv.org/abs/0704.0175
...
6
votes
0answers
85 views
How scientists could say that such meteorite comes from Mars
How could scientists affirm that a meteorite comes from Mars and not from another source ?
This is a probability or an absolute certainty ? How much percent ?
4
votes
0answers
38 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 ...
4
votes
0answers
34 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?
...
4
votes
0answers
94 views
Relation between isophotal radius and virial radius in spiral galaxies?
Is there any (proposed) relation between the B-band isophotal radius of a spiral galaxy and its virial radius (r_200)?
If you know of such a relation, please post a reference paper.
3
votes
0answers
49 views
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 ...
2
votes
0answers
135 views
Angular Diameter, Parallax - Perceived size of Objects
I'm currently in the process of writing a 2.5D Application that should display the perceived size of an Object. For example, When I have a ball that has a diameter of 1meter, how big would it appear ...
2
votes
0answers
75 views
Surface normal on the earth to the sun at a given point in time
How complicated is it to calculate a surface normal on the spherical approximation of the earths surface pointing towards the sun at a given point in time?
What I try do is to highlight a small area ...
1
vote
0answers
54 views
Could Voyager 1 have entered a solar radiation belt?
We currently believe that the Sun has no radiation belts because the unstable magnetic field, which turns every 11 years, is not stable enough to sustain a solar radiation belt. But observations from ...
1
vote
0answers
72 views
Does quantum Zeno effect play role in astrophysics?
For example, do two galaxies situated in proximity reduce the atom decay rate in each other?
What happens with decay quanta escaped to infinity? Does the radius of apparent horizon effect the ...
1
vote
0answers
49 views
Why does $H_2$ form on such a long time scale?
If we were trying to figure out the time scale for a gas-phase reaction between two hydrogen atoms in a molecular cloud (which has density $~10^4/$cm$^3$), apparently the reaction would happen on a ...
1
vote
0answers
57 views
Thermal gravitational radiation and its detection
To my poor knowledge on the topic, the gravitational waves that are most likely to be detected by LIGO or other experiments do not have thermal spectrum. But I'm not certain.
I know that Hawking's ...
1
vote
0answers
67 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 ...
0
votes
0answers
81 views
Is the fuel burn for a satellite launch affected by the position of the moon relative to the launch site?
The gross mass of a satellite rocket is tiny compared to that of Earth, and Luna. Between them, however, the two bodies set up tides in bodies of water which itself is again considerable mass.
At ...
0
votes
0answers
55 views
Space-time & solar mass
Does the space-time curvature described by Einstein have any affect on the accuracy of our determination in the age of a star or globular cluster? How does this affect our interpretion of how old we ...
0
votes
0answers
81 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 ...
0
votes
0answers
100 views
Cross section of photoelectric absorption vs Thomson scattering cross section
I am interested in more less the same issue as asked here but my question is:
Why for the low X-rays the photoelectric absorption is dominant over Thomson/Compton scattering? I am considering the ...
-1
votes
0answers
104 views
When can a body of water glow in space?
How would superionic water be formed at the core of a giant water planet? The publication
Giant planets may host superionic water, E. Marris, Nature News, 22 March 2005,
states that water in ...
