Iota Ursae Majoris (ι UMa / ι Ursae Majoris) is a star system in the constellation Ursa Major. It is approximately 47.7 light years from Earth. It has the traditional names Talitha Borealis and Alphikra Borealis, and was also named Dnoces ("Second," backwards) after Edward H. White II, the United States' first spacewalker. 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. ... A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ... Jump to: navigation, search Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ... Edward White Edward Higgins White, II (November 14, 1930 - January 27, 1967) was an American astronaut. ... Astronaut Bruce McCandless on an untethered EVA Extra-vehicular activity (EVA) is work done by an astronaut away from the Earth and outside of his or her spacecraft. ...

The Iota Ursae Majoris system is composed of two binary stars. The brightest component, Iota Ursae Majoris A, is a white A-type subgiant with an apparent magnitude of +3.12. It is a spectroscopic binary whose components have an orbital period of 4028 days. A binary star system consists of two stars both orbiting around their barycenter. ... 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. ... Subgiant star is a class of stars that are brighter than normal main sequence (dwarf) stars, but not as bright as true giant stars. ... 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. ... 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. ...

The companion binary is composed of the 9th magnitude Iota Ursae Majoris B and the 10th magnitude Iota Ursae Majoris C. These two stars orbit around each other with a period of 39.7 years, and are separated by roughly 0.7 arcseconds, or at least 10 Astronomical Units (AU). The two binary systems orbit around each other once every 818 years. The separation between the two binaries is rapidly decreasing as they follow their orbits. In 1841 when the B component was first discovered, they had a separation of 10.7 arcseconds, or at least 156 AU. By 1971 their separation had decreased to 4.5 arcseconds, or at least 66 AU. 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. ... 1841 is a common year starting on Friday (link will take you to calendar). ... 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. ... Jump to: navigation, search 1971 is a common year starting on Friday (click for link to calendar). ... 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. ...