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programming numerical algorithms for astrophysical applications.


Jan
10
revised Does gravity slow or speed light up?
added 404 characters in body
Jan
10
answered Does gravity slow or speed light up?
Jan
10
revised How can the life time of a multiple star system, such as for example the trinary system PSR J0337+1715 be derived?
edited body
Jan
10
answered How can the life time of a multiple star system, such as for example the trinary system PSR J0337+1715 be derived?
Jan
10
comment Heavy star and redshift
@frodeborli At cosmological red-shift 1000 there are no stars.
Jan
9
revised Heavy star and redshift
deleted 3 characters in body
Jan
9
answered Heavy star and redshift
Jan
9
answered What's the largest non-spherical astronomical object in the universe?
Jan
9
comment Could something temporarily break the Moon's tidal lock?
@Envite You may be right here. The mass distribution of the Moon is not exactly spherical w.r.t. its centre of mass (the lowest order deviation is described by its quadrupole) and therefore, there will be a favourable orientation which minimizes the gravitational energy. However, it's not clear that the (global) minimum is very prominent: there may be several minima of comparable depth, when it shall be random which one is picked.
Jan
7
revised Two species of dark matter?
added 37 characters in body
Jan
7
comment Two species of dark matter?
@AlexeyBobrick So, which theory naturally contains two different (one hot, one cold) species of DM particles in roughly equal proportions (so that no either dominates)? The other answer does not explain why such theories are not seriously considered. AFAIK, a mix of particles hot and cold particles cannot currently be ruled out, but Occam's razor is used.
Jan
6
awarded  Organizer
Jan
6
revised Why don't we see the galaxy center?
removed unrelated tag
Jan
6
comment Could something temporarily break the Moon's tidal lock?
with the same face towards us -- that is surely wrong: which face the moon will show must be a random effect.
Jan
6
suggested suggested edit on Why don't we see the galaxy center?
Jan
6
comment How does a telescope measure parallax angle?
Perhaps it's worth adding that the mean position is usually not fixed, but (for single stars) moves (nearly) on a line. This motion is called proper motion and measured from the same type of data (stellar positions over several epochs) as the parallax.
Jan
6
comment Two species of dark matter?
@AlexeyBobrick Occam's razor says we should not start playing with more than one different DM particle type, unless there is convincing independent evidence or theory to the opposite. Here, a theory is not just a simple model (messing around), but a prediction for the relation between two DM species which naturally emerges from some deeper insight. So, if your "A+B" is a theory in this sense, then Occam's razor doesn't apply. However, AFAIK, no such DM theories with more than one species are currently seriously considered.
Dec
31
comment Which planet or moon has all resources that can be used to sustain life in a controlled biosphere?
@Moriarty sorry. I thought you sanctioned that edit.
Dec
30
revised Two species of dark matter?
added 13 characters in body
Dec
30
revised Which planet or moon has all resources that can be used to sustain life in a controlled biosphere?
major editing to improve the answer; added point about cosmic radiation and low gravity.