Astronomers have recently found that magnetic fields inside stars are highly magnetized using a technique known as asteroseismology. Asteroseismology is used to observe the inner structure of stars using their oscillations. A star can be observed at various depths with different oscillation types. Two oscillation types are typically used: gravity modes and acoustic modes. Gravity modes have a smaller frequency with a high buoyancy, and acoustic modes have a large frequency with a high pressure.
These astronomers think that observing the magnetic fields of stars can help them understand the rotation rates, which play a large role on the lifetime of stars and the magnetic fields they generate. The rotation rate of a star can vary as its forming and even after it has formed. When a star first forms, it starts off with a cloud of gas and dust that collapses and rotates. During this process, the rotation rate of the cloud of gas continues to get higher until it eventually slows down, and a star is finally able to form. Stars can gradually lose mass as time goes by due to stellar wind, causing the rotation rate to decrease. Stars with a high rotation rate tend to lose mass quickly and experience a rapid decrease in rotation rate.
One of the things they found was that red giants have a core that is much denser than other stars. Because of this, sound waves are unable to reflect from the core and become gravity waves, resulting in unique oscillations. These gravity waves travel all the way to the core of a star and can get trapped there by the star's magnetic fields, which can result in some of the star's oscillation energy to disappear.
They also discovered that red giants have strong magnetic fields. Strong magnetic fields play a large role in how these stars evolve. These magnetic fields are similar to white dwarfs and are even 10 million times greater than the Earth's magnetic field.
Source: http://www.sciencedaily.com/releases/2015/10/151022161230.htm
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