Stars Have Magnetic Personalities

star magnetic field

star magnetic field

Magnetism is more than merely an attractive attribute.  It seems to be a common one, as well.

Consider: The Sun, like the Earth, has its own magnetic field.  In some places, this field is strong enough to produce sunspots and other dramatic features.  But on average, the Sun’s magnetic field is only about twice that of Earth’s. 

It’s long been thought that most stars would be similar to the Sun – sporting only relatively weak magnetism.  But an international group of astronomers, including SETI scientist Daniel Huber, has discovered that strong magnetic fields are actually common for stars. Using data from NASA’s Kepler mission, the team found that stars slightly more massive than the Sun have internal magnetic fields up to 10 million times that of the Earth.  This finding has important implications in understanding how stars age.

The discovery was made using a technique called asteroseismology, which uses the measurement of stellar oscillations, or sound waves, to probe below the surface of a star. The team measured tiny brightness variations caused by these sound waves in more than 700 so-called red giant stars, and found certain oscillation frequencies were missing in 60 percent of the stars because they were suppressed by strong magnetic fields in the stellar cores. The technique of asteroseismology has also been used to precisely characterize the host stars of exoplanets discovered by Kepler.

These results will enable scientists to more directly test how magnetic fields form and evolve inside stars – a mechanism known as a magnetic dynamo. This may lead to a better general understanding of this process, including the dynamo controlling the Sun’s 22-year magnetic cycle, which is known to affect communication systems and cloud cover on Earth.