Iota Ursae Majoris is a star of magnitude 3.14 in one of three close (but physically unrelated) pairs of stars that make up the feet of Ursa Major, the Great Bear. In Arabic culture, the three represent the "leaps" of a gazelle; Talitha and Kappa Ursae Majoris make up the westernmost "third leap". The name Talitha actually comes from the Arabic number three.
The star was also named Dnoces ("second," spelled backwards) after Apollo astronaut Edward H. White II. The name was invented by his fellow astronaut Gus Grissom as a practical joke, but has endured as memorial to both astronauts, who perished in the 1967 Apollo 1 fire.
Properties and Components
Talitha is approximately 47.7 light years from Earth, and is composed of two binary star systems. The brightest component, ι UMa A, is a rather youthful, 1.7 solar-mass white class A7 IV star, with a temperature of 8165 K, and a luminosity 9 times the Sun's. It is also a spectroscopic binary, whose components have an orbital period of 4028 days (11 years) and orbit at a distance of 5 or 6 AU.
The companion binary is composed of 9th magnitude ι UMa B and 10th magnitude ι UMa C. These two stars are pair of class M1 V dwarfs that orbit each other with a period of 39.7 years, and are separated by roughly 0.7", or at least 10 AU. The two binary systems circle each other once every 818 years, in an orbit averaging 132 AU in radius. The apparent separation between the two binaries is rapidly decreasing: in 1841, when the B component was first discovered, they had a separation of 10.7"; by 1971, their separation had decreased to 4.5".
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]