Iota Tri (6 Tri)

For any size telescope

Iota Tri (6 Tri, TZ Tri, HR 642, HD 13480, SAO 55347, PPM 67067, HIP 10280, GC 2633, ADS 1697, Struve 227) is a colorful double star made up of a yellow, 5th magnitude GO III primary and an apparently light-blue 6.8 magnitude F6 V companion. The stars are currently separated by 3.9".

The primary star is the variable star TZ Tri, a rotating ellipsoidal variable. TZ Tri is actually a very close pair of stars that orbit about their common center of mass. They are so close together that the stars are stretched by gravity into teardrop shapes. When we see the teardrops end-on the light from the stars is less than when we see them broadside. For this reason the total light of the star varies from 5.19 to 5.28 magnitude as they orbit. It takes them 14 days, 8 hours and 47 minutes to complete one orbit. In addition, these stars are also of the RS CVn type resulting in additional variability that is due to eruptions in their chromospheres and coronae.

According to Burnham's, this double was probably discovered by William Herschel in 1781.


The view in a 6" at 270x. North is down and east is right.