TALITHA (Iota Ursae Majoris). Three close (but physically unrelated) pairs of stars make the feet of Ursa Major, the Great Bear. In Arabic culture, the three represent the "leaps" of a gazelle, Talitha (Bayer's "Iota" star) and Kappa Ursae Majoris making (and meaning) the westernmost "third leap" (the name actually coming from the number 3). The other two "leaps," Tania and Alula, are divided into northern and southern (Tania Australis and Borealis and Alula Australis and Borealis), but for some odd reason not Talitha, which belongs exclusively to the northern of the pair. Talitha, in simplest form a cooler class A (A7) star 48 light years away, is on closer look a complex multiple. The main component third- magnitude (3,14) A7 star has a temperature of 8165 Kelvin and a luminosity 9 times that of the Sun. Though classed from its spectrum as a "subgiant," a star whose internal hydrogen core is running (or has run) out of fuel, placement by temperature and luminosity show it to be a rather youthful 1.7 solar mass star that has a lot of hydrogen-fusion time left to it. Four seconds of arc away, in an orbit averaging 132 Astronomical Units in radius, is a reddish 10th magnitude companion that takes 818 years to make a full circuit. The companion is itself a double, a pair of class M (M1) dwarfs that take 40 years to circle each other at a distance of 10 Astronomical Units (about Saturn's distance from the Sun). Returning to the bright class A star, it again is double, the companion, about which nothing is known, taking 11 years to orbit at a rough distance of 5 or 6 Astronomical Units. From the M star double, were there an orbiting planet (which almost certainly there is not), the bright A star would shine nearly 500 times more brightly than our full Moon, the small companion at most 2.5 degrees away, while from the bright star (again a planet highly doubtful), the class M double would in combination cast a reddish light about equal to that of our full Moon, the two at most a bit over four degrees apart.
Written by Jim Kaler. Return to STARS.