The solar corona, the extremely hot gaseous outer shell of the Sun, produces flares and mass ejections that can disrupt communication on Earth. Although observations of the Sun are helping to connect coronal variability with the magnetic field, researchers would also like to observe the detailed structure of other stars to explore their similarities and differences.
Brickhouse et al. have used the dynamics of a nearby binary system, 44i Bootis, in constellation Bootes, and the high resolution afforded by the Chandra x-ray observatory to image the structure of a stellar corona. The two stars of 44i Bootis are in close orbit and pass in front of each other every 3 hours. These authors analyzed Doppler-shifted lines in the x-ray emission spectrum from coronal structures on the primary star as the secondary moved in front of it and behind it, in an observationally fortuitous game of hide and seek. The strength of coronal activity at high latitudes (the polar regions of these stars) was unexpected and contrasts with the behavior of the Sun.—LR
Astrophys. J.562, L75 (2001).