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Vega's proper motion is 202.03 ± 0.63 milliarcseconds (mas) per year in right ascension—the celestial equivalent of longitude—and 287.47 ± 0.54 mas/y in declination, which is equivalent to a change in latitude. The net proper motion of Vega is 327.78 mas/y, [83] which results in angular movement of a degree every 11,000 years.
Right ascension is measured eastward up to 24 h along the celestial equator from the primary direction. Right ascension (abbreviated RA; symbol α) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the Earth. [1]
Right ascension: 18 h 44 m 20.34589 s [1] Declination +39° 40′ 12.4533 ... both binaries have moved only a few degrees in position angle. The component stars of ...
The primary is an A-type main sequence star, [19] and the secondary has half the mass of the Sun. [18] η Aql is a yellow-white-hued supergiant star, 1200 light-years from Earth. Among the brightest Cepheid variable stars , it has a minimum magnitude of 4.4 and a maximum magnitude of 3.5 with a period of 7.2 days. [ 1 ]
In this case, the longitude is also called the right ascension of the ascending node (RAAN). The angle is measured eastwards (or, as seen from the north, counterclockwise) from the FPA to the node. [2] [3] An alternative is the local time of the ascending node (LTAN), based on the local mean time at which the spacecraft crosses the equator.
Were the Sun to be observed from this star system, it would appear to be a magnitude 2.55 star in the constellation Aquila with the exact opposite coordinates at right ascension 19 h 39 m 18.11950 s, declination −05° 13′ 29.9552″.
Deneb is one of the vertices of the asterism known as the Summer Triangle and the "head" of the Northern Cross. It is the brightest star in Cygnus and the 19th brightest star in the night sky, with an average apparent magnitude of +1.25. Deneb rivals Rigel, a closer blue supergiant, as the most luminous first-magnitude star.
Conjunction in right ascension and conjunction in ecliptic longitude do not normally take place at the same time, but in most cases nearly at the same time. However, at triple conjunctions , it is possible that a conjunction only in right ascension (or ecliptic length) occurs.