111 Tauri

Lore & Background

The primary star of 111 Tauri is larger and more luminous than the Sun, with about 130% of the Sun's radius and 185% of its luminosity. Its metallicity is similar to the Sun, with estimates of [Fe/H] ranging from −0.14 to 0.05. The star shows an unusually high content of lithium, which remains unexplained. Age estimates for this star range from 3.6 to 3.76 billion years, though the most recent age determination indicates a very young star with an age of 20 to 50 million years. It is a prominent X-ray source.

The star rotates relatively rapidly, completing a rotation along the equator every 3.5 days compared to 25 days for the Sun, and it undergoes differential rotation with varying velocity by latitude. In 1996, Kazimierz Stępień and Edward H. Geyer announced that 111 Tauri is a variable star, and it was given the variable star designation V1119 Tauri in 1997. The secondary component, Gliese 201, is a K-type main sequence star.

Reader's Guide

111 Tauri, as V1119 Tauri, is a BY Draconis variable, a class of stars whose variability arises from starspots and rotation. Its rapid rotation and differential rotation contribute to its brightness fluctuations, making it a useful object for studying stellar activity and magnetic phenomena. The star's membership in the Hyades stellar kinematic group of co-moving stars places it within a well-studied moving group, aiding in understanding stellar evolution and kinematics. The unresolved discrepancy in its age—ranging from billions to tens of millions of years—highlights ongoing challenges in stellar age determination. Its high lithium content, unexplained by current models, adds to its astrophysical interest. The system's wide binary nature and the primary's X-ray emission further characterize it as a nearby laboratory for studying young, active stars and binary star dynamics.

Did You Know?

• The primary star rotates once every 3.5 days, much faster than the Sun's 25 days.
• The star is a member of the Hyades stellar kinematic group of co-moving stars.