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comment Is it possible to create a traditional clock solar system?
@William You accepted my answer but didn't upvote it. Why do you think this answer is acceptable but still poor?
Jun
10
comment How do we know Milky Way is a 'barred' spiral galaxy?
@RobJeffries psst about that walter here.
Jun
10
comment How do we know Milky Way is a 'barred' spiral galaxy?
@RobJeffries Look at my article and any quoting it.
Jun
1
comment Why are all quasars so far away?
I disagree with you on the strangeness of creation of matter. With the big-bang, it's restricted to a single event with clear observational implications. With the steady state theory, it is required frequently and pervasively without any observational evidence.
May
31
comment Potential Re-Capture of Rogue Planets
Nice to see you quote Melvyn (et al). One thing all these studies (as well as my answer above) ignore, I think, it the possibility of tidal capture (or the aid of tidal dissipation in dynamical capture) and the role of tides in the orbital evolution of captured planets.
May
31
comment Why are all quasars so far away?
There is still more than enough gas to make for a good quasar. The critical question is how much of that is funneled close enough to the black-hole binary (which will form) and then how much will actually accrete onto one of the holes (rather than being ejected via gravitational slingshot).
May
30
comment Why are all quasars so far away?
Okay, but the steade state theory requires strange physics (in the sense of my previous comment), namely generation of matter out of nothing as the universe keeps expanding. In fact, the steade state theory is just such a rubbish that I keep wondering how it ever could attract as much attention as it did.
May
30
comment Why are all quasars so far away?
Indeed, the collision of M31 with the Milky Way will most likely trigger some quasar activity. The black hole at the centre of M31 is $~100$ times as massive as that of our galaxy and can make for a pretty bright quasar.
May
30
comment Why are all quasars so far away?
I think Olber's paradox is the most obvious objection to the perfect cosmological principle. It can only be resolved if the universe is finite, either in space or in time (or both or some strange physics such as tiring light).
May
30
comment Why are all quasars so far away?
Nearby quasars would be even more interesting (since they allow detailed observations), but all of those are long known. Intermediate-redshift quasars (at $z\sim1-4$) are plenty and too distant for detailed investigations.
May
3
comment What is the most populated/numerous stellar system in which the orbits of all objects are known?
The Solar system is the only system for which all the major bodies and their orbits are known.
May
3
comment Why does the Solar System have no (natural) satellites of satellites?
Are you referring to the Kozai-Lidov effect? This only works for sufficiently inclined orbits, but orbits (around the moon) in the same plane as the Moon-Earth orbit should be stable (Solar tides are much weaker and the inclination is small).
May
3
comment Star versus Black Hole
@SwapnilRastogi As I said in the answer, some of the stellar matter [from the star ripped apart] forms an accretion disc around the BH. This is essentially all matter that is gravitationally bound to the BH. The remainder escapes. If the star was initially on a parabolic orbit (which to good approximation is the typical situation), half of the gas from the star will accrete and the other half escape.
Apr
14
comment Can stars be observed from space by x-rays, near infrared and radio wavelengths?
No, "seen" implies the human eye, which is incapable of sensing in these wavelengths. Or didn't you mean that?
Feb
27
comment Fourier Transform of Galaxy Images
The Fourier transform per se will not help you to find overlapping object. Where does this idea come from?
Feb
6
comment Why there are other planets in our solar system?
Are you asking for the reason (that there are planets) or for their purpose?
Feb
6
comment Why there are other planets in our solar system?
Why are there other people on this planet. Only I am important. What is the significance of others, such as user804401? I receive food from the plants and animals. In a similar way do I receive any food from other people?
Feb
6
comment Does one need to take into account finite gravity speed in N-body simulations?
Most large-scale N-body simulations (e.g., stellar clusters, galaxies, galaxy clusters, ...) use general relativity Wrong For up to galaxy scales, one safely uses Newtonian gravity. For larger scales (so-called cosmological $N$-body simulations), one uses GR only to describe the (assumed) smooth background (universal expansion), but Newtonian physics otherwise.
Feb
6
comment Galaxy rotation curve and dark matter
The authors of that book should have mentioned the caveat, that it only introduces a small error, and that in the scientific literature (of which that book is no part) such simplifications are not made (unless the errors introduced are far smaller than other sources of error). If they did not, then this is just another example of poor practice in presenting science to the public.
Feb
5
comment Galaxy rotation curve and dark matter
Can you substantiate your claim (that galaxy rotation curves are calculated from what you call the shell theorem)? For near-spherical object, the error one makes with this assumption is very small (at most a few %).