Xi Ursae Majoris (ξ UMa / ξ Ursae Majoris) is a star system in the constellation Ursa Major. It also has the traditional name Alula Australis. In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... Jump to: navigation, search The J2000. ... Jump to: navigation, search Orion is a remarkable constellation, visible from most places on the globe (but not always the whole year long). ... Ursa Major (Ursa Maior in Latin) is a constellation visible throughout the year in the northern hemisphere. ... Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ... Jump to: navigation, search The parsec (symbol pc) is a unit of length used in astronomy. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequenly refined in terms of other characteristics. ... The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ... In astronomy, many stars are referred to simply by catalogue numbers. ... The Henry Draper Catalogue is an astronomy catalogue with astrometric and spectroscopic data about more than 225,000 stars. ... In astronomy, many stars are referred to simply by catalogue numbers. ... In astronomy, many stars are referred to simply by catalogue numbers. ... In astronomy, many stars are referred to simply by catalogue numbers. ... In astronomy, many stars are referred to simply by catalogue numbers. ... A star system or stellar system is a group of stars (and possibly smaller bodies such as planets or asteroids) that orbit one another (systems with planetary bodies orbiting stars, are referred to as solar systems or planetary systems). ... Jump to: navigation, search Orion is a remarkable constellation, visible from most places on the globe (but not always the whole year long). ... Ursa Major (Ursa Maior in Latin) is a constellation visible throughout the year in the northern hemisphere. ...

The system is composed of a double star whose two components are yellow G-type main sequence dwarfs. The brighter component, Xi Ursae Majoris A, has a mean apparent magnitude of +4.41. It is classified as an RS Canum Venaticorum type variable star and its brightness varies by 0.01 magnitudes. The companion star, Xi Ursae Majoris B, has an apparent magnitude of +4.87 and is separated from the primary by 0.05 arcseconds. The orbital period of the two stars is 1.83 years and they are separated by 1.2 arcseconds, or at least 10 Astronomical Units. Xi Ursae Majoris was the first visual double star for which an orbit was calculated, when it was computed by Félix Savary in 1828. Double Star is a science fiction novel by Robert A. Heinlein. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequenly refined in terms of other characteristics. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ... RS Canum Venaticorum variables are a type of variable star. ... Most stars are of nearly constant luminosity. ... A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ... A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ... The astronomical unit (AU or au or a. ... See also: Other events of 1828 List of years in science . ...

Each component of this double star is itself a spectroscopic binary. The A binary star has the same orbital period, 1.83 years, as the AB system, due to tidal interactions. B's binary companion, denoted Xi Ursae Majoris Bb, is unresolved, but the binary star is known to have an orbital period of 3.98 days. A spectroscopic binary star is a binary star which cannot be resolved as a visual binary, even with telescopes of the highest existing resolving power. ...