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Jul
24
comment Could dark matter particles be unstable?
en.wikipedia.org/wiki/Baryonic_dark_matter
Jul
24
comment Could dark matter particles be unstable?
@Aaron this is not how Dark Matter is defined in Astronomy, when we make rotation profiles for galaxies. Dark matter is ordunary matter, but just dark=unobservable.
Jul
17
comment The RA and Dec of lunar poles
@questionhang Just use Cassini's Laws. If you have trouble with them that's another question. This one is over.
Jul
17
comment The RA and Dec of lunar poles
@questionhang Double check the link I have just provided. The angle between the ecliptic and the lunar equator is always 1.543° and the rotation axis of the Moon precesses with the same rate as its orbital plane, but is 180° out of phase (see Cassini's Laws). This is all you need. You just need to follow the link to Cassini's Laws. Did you really investigate before asking?
Jul
16
comment The RA and Dec of lunar poles
@questionhang en.wikipedia.org/wiki/Orbit_of_the_Moon#Inclination
Jul
11
comment Why is right ascension measured in hours?
@Dieudonné No, you can not define a time unit as an angle, they are different magnitudes. You can, instead, define a time unit by using an angle: a sidereal second is the time the Earth rotates 360/(24*60*60) degrees in reference to the fixed stars in average.
Jul
10
comment What is the difference between a dwarf spheroidal galaxy and a globular cluster?
Please note that I referred to be bound inside a larger body. SMC and LMC are not inside Milky Way.
Jul
10
comment Why is right ascension measured in hours?
@Dieudonné Moreover, a sidereal second is defined regarding Earth's rotation referring to "fixed stars" (so, to the catalog equinox). Please cf. en.wikipedia.org/wiki/Sidereal_time and the definition there: Sidereal time, at any moment (and at a given locality defined by its geographical longitude), more precisely Local Apparent Sidereal Time (LAST), is defined as the hour angle of the vernal equinox at that locality: it has the same value as the right ascension of any celestial body that is crossing the local meridian at that same moment. Since it is defined as HA, it is a time.
Jul
9
comment Why is right ascension measured in hours?
@Dieudonné You are wrong. Sidereal time is a time, measured in Sidereal seconds, not in degrees.Please check e.g. Wikipedia: en.wikipedia.org/wiki/Sidereal_time Local Sidereal Time at any locality differs from the Greenwich Sidereal Time value of the same moment, by an amount that is proportional to the longitude of the locality. When one moves eastward 15° in longitude, sidereal time is larger by one sidereal hour (note that it wraps around at 24 hours). I have actually used sidereal time clocks in my observations.
Jun
24
comment Is there a flaw with the newer purposes and correlations attributed to the HR diagram? (And would a third axis of mass correct the enclosed flaw?)
You need to write an article about the 3D diagram, its advantages, some use cases, fancy images, and send it to some academic magazine.
May
28
comment What study profiles could land me the job of Astronomer?
This question appears to be off-topic because it is about professional skills
May
21
comment Calculate telescope orientation based on RA, DEC and Lat/Long
What do you need to calculate? DEC and RA are the celestial coordinates, so they are "where" the telescope is pointing at.
May
21
comment What does “Normalized to Si 10 to the power 6” mean?
Could you please provide a link to that table? Maybe it is easier to interpret it directly than from your explanation.
May
19
comment Why planet's orbit is not perpendicular or random ?
Typical deflection time does not mean that all deflections take place at that moment. There are deflections way before that. Think in typical height for men in your country. Are there men higher than that? And shorter?
May
13
comment Motion of the sun as observed from mercury
The combination of two movements, one "horizontal" with forward and backward and one "vertical" caused by the inclination of the Axis, the same one we experience on Earth where Sun is higher in sky in summer and lower in winter.
May
12
comment Why planet's orbit is not perpendicular or random ?
Elliptical galaxies are dwarf galaxies, sort of giant globullar clusters, so they have had the same processes as globullar clusters, including huge amounts of interactions and ejections. Each star, indeed, keeps its own Angular Momentum, and the system as a whole (elliptical galaxy plus ejected stars) does as well, but the galaxy not counting the ejections, which is the observable body, does not.
May
12
comment Why planet's orbit is not perpendicular or random ?
The intercation among stars on galaxies is very tiny. Globular clusters have a density of 10^5 to 10^6 stars in a very small sphere (on the magnitude of 1pc, almost never reaching 10pc), while galaxies have a density of 10^11 or 10^12 stars in an enormous disk (on the magnitude of 10^4 or 10^5pc)
May
12
comment Why planet's orbit is not perpendicular or random ?
The orbits of stars on a globullar cluster are seemingly random due to the enormous amount of interactions they have had among the stars, including ejections of some individuals that effectively change the angular momentum of the cluster.
May
9
comment Triangular Asterism Trigonometry
Question is not clear. Do you want spherical triangle formulas? Or real space ones?
May
8
comment Motion of the sun as observed from mercury
@Yashbhatt Yes, It is :)