T_Cygni
T Cygni
Variable star in the constellation Cygnus
T Cygni is a binary star[9] system in the northern constellation of Cygnus. It is a faint system but visible to the naked eye with a combined apparent visual magnitude of 4.93.[2] Based upon an annual Parallax shift of 8.4 mas,[1] it is located 387 light years away. It is moving closer to the Earth with a heliocentric radial velocity of −24 km/s.[6]
The primary, component A, is a variable star, most likely of the slow irregular type, which ranges in magnitude from 4.91 down to 4.96.[5] It is a giant star with a stellar classification of K3 III,[4] which indicates it has exhausted the hydrogen at its core and evolved away from the main sequence. The star has expanded to 28 times the radius of the Sun.[1] It is radiating 241 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,285 K.[1]
The secondary companion, component B, is a magnitude 10.03 star located at an angular separation of 8.10″ along a position angle of 120°, as of 2012. In 1877 it was separated by 10.0″ with nearly the same position angle (121°).[3]