The star V889 Hercules demonstrates an unusual rotation profile that contradicts all known models of stellar dynamics. Astronomers have discovered that its mid-latitudes rotate faster than the equator and the poles.
Unlike the Sun, where the equator rotates faster than the poles, V889 Hercules has a maximum rotation speed at latitudes of 37-40 degrees. The equator moves more slowly, and the poles have the lowest rotation speed. This model contradicts all scientists’ expectations.
The study was conducted by a group of scientists led by Mikko Tuomi from the University of Helsinki. They applied a new statistical method to data collected over 30 years of observations.
«We did not expect to see such anomalies in stellar rotation. This indicates that our understanding of stellar dynamics and magnetic dynamos is inadequate,» Tuomi said.
The scientists also studied LQ Hydra — a star 20% less massive than the Sun and of the same age as V889 Hercules. Its rotation did not differ from that of a solid body, where the equator and poles rotate at the same speed. However, scientists assume that the equator of LQ Hydra does rotate a little faster, but the difference is so small that it cannot be detected by modern methods.
Robotic telescopes of the Fairborn Observatory were used for the observations. Although these instruments cannot see individual star spots at such a distance, they compensate for this by making long-term observations of changes in the brightness of stars.
«It is amazing that even in the age of large space observatories, we can obtain fundamental information about stellar astrophysics with small ground-based telescopes with a diameter of 40 cm [16 inches],» Tuomi said.
Research published in the journal Astronomy & Astrophysics.
Source: Iflscience