An intriguing phenomenon surrounds the rotation of V889 Herculis, a star similar to our Sun but also so different. Located about 115 light-years away, this star defies established stellar models by rotating faster at a latitude of approximately 40 degrees, unlike our Sun which reaches its maximum speed at the equator.
V889 Herculis, a nearby star, rotates fastest at a latitude of about 40 degrees. This unusual rotational profile challenges established stellar models.
Credit: Jani Närhi, University of Helsinki
Researchers at the University of Helsinki discovered this atypical rotation by applying an innovative statistical technique to known data. The detected anomalies suggest that our understanding of stellar dynamics and magnetic dynamos is incomplete.
Mikko Tuomi, who coordinated the study, emphasizes that this discovery is crucial to better comprehend the physics of stars, particularly in predicting activity phenomena on the solar surface, such as spots and flares.
Stars, dynamic plasma spheres, do not have solid surfaces. Their differential rotation is caused by plasma convection, affecting rotation speed at different latitudes. However, factors such as stellar mass, age, chemical composition, rotation period, and magnetic field also influence this phenomenon.
The team also studied a second star, LQ Hydrae, which showed a more uniform rotation. These results were obtained through long-term observations conducted at Fairborn Observatory, led by senior astronomer Gregory Henry, which allowed tracking brightness variations over several decades.
The target stars, V889 Herculis and LQ Hydrae, are very young, around 50 million years old, and rotate rapidly, with rotation periods of about a day and a half. These observations provide detailed rotational cycles, essential for understanding the physics of young and active stars.