from Nature 522, 131 (11 June 2015) doi:10.1038/522131d
Astronomers have spotted an enormous surge of light and magnetic energy on a nearby star.
A team led by Wouter Vlemmings at Chalmers University of Technology near Gothenburg, Sweden, pointed the ALMA radio telescope in northern Chile at the red giant Mira A, a star 92 parsecs (300 light years) away that was once like our Sun but is now bloated in old age. ALMA’s high resolving power was able to pick out features on the stellar surface — a feat unprecedented at these wavelengths. The data revealed a bright hotspot on Mira’s surface that is roughly the same size as Mercury’s orbit around the Sun.
The star is probably unleashing energy from its magnetic field, similar to what happens on the Sun, suggesting that magnetic fields have a role even when these stars grow old.
Paper: Resolving the stellar activity of the Mira AB binary with ALMA⋆