Stellar magnetic field
A localized magnetic field exerts a force on the plasma, effectively increasing the pressure without a comparable gain in density.
The first instrument to be dedicated to the study of stellar magnetic fields was NARVAL, which was mounted on the Bernard Lyot Telescope at the Pic du Midi de Bigorre in the French Pyrenees mountains.
[4] Various measurements—including magnetometer measurements over the last 150 years;[5] 14C in tree rings; and 10Be in ice cores[6]—have established substantial magnetic variability of the Sun on decadal, centennial and millennial time scales.
If the gas or liquid is very viscous (resulting in turbulent differential motion), the reversal of the magnetic field may not be very periodic.
Due to the differential rotation of the star, the tube becomes curled up and stretched, inhibiting convection and producing zones of lower than normal temperature.
By contrast middle-aged, Sun-like stars with a slow rate of rotation show low levels of activity that varies in cycles.
This results in a transfer of angular momentum from the star to the surrounding space, causing a slowing of the stellar rotation rate.
The magnetic field of these stars is thought to interact with its strong stellar wind, transferring angular momentum to the surrounding protoplanetary disk.
The flares on this class of stars can extend up to 20% of the circumference, and radiate much of their energy in the blue and ultraviolet portion of the spectrum.
[18] Radio observations also suggest that their magnetic fields periodically change their orientation, similar to the Sun during the solar cycle.
[19] Planetary nebulae are created when a red giant star ejects its outer envelope, forming an expanding shell of gas.
The rapid rotation of these collapsed neutron stars results in a pulsar, which emits a narrow beam of energy that can periodically point toward an observer.
Compact and fast-rotating astronomical objects (white dwarfs, neutron stars and black holes) have extremely strong magnetic fields.
The magnetic field of this star has increased the surface temperature to 18 million K and it releases enormous amounts of energy in gamma ray bursts.
[22] Jets of relativistic plasma are often observed along the direction of the magnetic poles of active black holes in the centers of very young galaxies.
Theoretical research since 2000 suggested that an exoplanet very near to the star that it orbits may cause increased flaring due to the interaction of their magnetic fields, or because of tidal forces.
In 2019, astronomers combined data from Arecibo Observatory, MOST, and the Automated Photoelectric Telescope, in addition to historical observations of the star at radio, optical, ultraviolet, and X-ray wavelengths to examine these claims.
Their analysis found that the previous claims were exaggerated and the host star failed to display many of the brightness and spectral characteristics associated with stellar flaring and solar active regions, including sunspots.
