109 Herculis
109 Herculis, also named Tusizuo, is a single star in the northern constellation of Hercules. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 3.84. The star is located around distant, based on parallax. It is moving closer to the Earth with a heliocentric radial velocity of −58 km/s, and may come as close as away in around 328,000 years.
This is an aging giant star with a stellar classification of K2IIIab. It is a red clump giant, meaning it is on the horizontal branch and is generating energy through helium fusion at its core. The star is roughly six billion years old with slightly more mass than the Sun. With the supply of hydrogen at its core exhausted, it has expanded to nearly 12 times the Sun's radius. The star is radiating 52 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,569 K.
Nomenclature
In Chinese astronomy, 109 Herculis is one of two stars in the asterism Tú Sì. It is named Tusizuo, meaning the left star in Tusi. The IAU Working Group on Star Names approved the name Tusizuo for 102 Herculis on 17 June 2025 and it is now so entered in the IAU Catalog of Star Names. The name Tusi was already in use for the asteroid 10269 Tusi, named after a Persian astronomer.This star, together with 93 Herculis, 95 Herculis, and 102 Herculis, formed Cerberus, the obsolete constellation.