Credit: Jan Robrade and ESA
Lights, Camera, Activity
Our Sun has an interesting periodicity - a cycle of magnetic activity which lasts roughly 11 years, during which the solar magnetic field strengthens, becomes tangled, and violently explodes, generating enormous eruptions from the solar atmosphere into interplanetary space. After 11 years the magnetic poles flip, and the cycle starts again. Detailed observations are helping astrophysicists understand the complex interactions driving the solar activity cycle. But the Sun is nearby and relatively easy to study. More distant stars are of course more difficult to study in detail, and besides, there are lots of them. Which ones have high energy activity cycles like our Sun? X-ray cameras can be used to study the high-energy radiation produced by the violent stellar magnetic flares associated with stellar active periods. But X-rays don't penetrate the earth's atmosphere, so a space-based observatory is needed. Also, these observations need to be taken over many years, requiring an observatory with a long lifetime. The XMM-Newton Observatory, along with the Chandra X-ray Observatory, have been in operation for more than a decade, and have been studying X-ray starlight for all that time. The image above shows two XMM-Newton observations of a nearby star system called 61 Cygni obtained over a span of 3 years. The image shows an obvious X-ray brightening of the star 61 Cygni A, while the emission from star 61 Cygni B seems mostly constant over that interval. The increase in brightness of 61 Cygni A's emission correlates with activity indicators measured at lower energies, closer to the star's surface.
Published: August 13, 2012
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