The sun rotates fastest at the equator and the rate of rotation slows down at higher latitudes, while in the polar regions it is the slowest. But a nearby Sun-like star, V889 Hercules in the Hercules group 115 light-years from Earth, rotates fastest at about 40 degrees latitude, while the equator and polar regions rotate more slowly
The sun rotates fastest at the equator and the rate of rotation slows down at higher latitudes, while in the polar regions it is the slowest. But a nearby sun-like star, V889 Hercules in the Hercules group 115 light-years from Earth, rotates fastest at about 40 degrees latitude, while the equator and polar regions rotate more slowly.
A similar rotation profile has not been observed in any other star. The result is amazing because the rotation of stars is considered a fundamental physical parameter that is well understood, but such a rotation profile was not predicted even in computer simulations.
"We applied a new statistical technique developed on the data of a well-known star that has been studied for years at the University of Helsinki. We did not expect to see such anomalies in the rotation of a star. The anomalies in the rotation profile of V889 Hercules indicate that our understanding of stellar dynamics and magnetic dynamo is insufficient," explains researcher Mikko Toomi, the study's coordinator.
The target star V889 Hercules is very similar to a young sun, and tells a story about the history and evolution of the sun. Tuoy emphasizes that it is essential to understand the astrophysics of stars in order, for example, to predict phenomena that cause activities, such as spots and storms.
Stars are spherical structures in which matter is in a plasma state, consisting of charged particles. They are dynamic objects that depend on the balance between the pressure created by nuclear reactions in their core and self-gravity. They do not have a solid surface, unlike many planets.
The stellar rotation is not constant at all latitudes - an effect known as differential rotation. It is caused by the fact that hot plasma rises to the surface of the star through a phenomenon called heat convection, which in turn affects the local rotation rate. This is because the angular momentum must be conserved and the heat conduction occurs perpendicular to the axis of rotation near the equator, while near the poles it is parallel.
However, many factors such as the star's mass, age, chemical composition, rotation time, and magnetic field affect the rotation and cause changes in the differential rotation profile.
Thomas Heckman, an astronomy lecturer who participated in the study, explains that the sun is the only star whose rotation profile could be studied.
"The differential rotation of a star is a very decisive factor that affects its magnetic activity. The method we developed opens a new window into the inner workings of other stars."
The Helsinki astronomers determined the rotation profile of two nearby young stars by running new statistical modeling on long-baseline observations of luminosity. They modeled the changes in rotation time in the observations by taking into account the differences in the apparent motion of the spots at different latitudes. The motion of the spots made it possible to estimate the rotation profiles of the stars.
Regarding the second target star, LQ Hydrae in the Water Serpent group, it was found to rotate like a rigid body - the rotation does not seem to change from the equator to the poles, meaning the differences are very small.
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Comments
Most of the planets in the universe (even if we don't include the moons and plutoids which by decision are currently not planets) have solid surfaces.
Simple explanation, in the area of the equator there is (gravitational) friction with invisible rings.