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Jul
25
answered How did the reionization epoch make the universe “transparent”?
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
23
revised Why can we sometimes see the moon during the day?
forgotten words
Jul
23
answered Are there standard algorithms and procedures for creating unique sky maps based on latitude/longitude/date/time?
Jul
18
answered Can Summer Triangle asterism be used for navigation?
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
16
answered The RA and Dec of lunar poles
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
10
answered What is the difference between a dwarf spheroidal galaxy and a globular cluster?
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.
Jul
9
reviewed Edit suggested edit on What is the explanation for rapid inflation just after the big bang?
Jul
9
revised What is the explanation for rapid inflation just after the big bang?
Corrected grammar for clarity,
Jul
9
awarded  Custodian
Jul
9
reviewed No Action Needed Is there a radius inside of which objects are (doppler) blue shifted?
Jul
8
revised Why is right ascension measured in hours?
Ops... I used North Horizon and it is South Horizon