The flare was eclipsed by the B star, enabling the scientists who first studied it to estimate its size and location. An immensely energetic magnetic flare was observed that lasted for nearly three days, and released a total X-ray energy of 10 37 erg -equivalent to the entire visible light output of the Sun for almost an hour and a million times more energetic than the largest solar flares. This is handy because when the B star passes in front of the K star the eclipse signature in X-rays can be used to infer the spatial structure of the K star's X-ray emitting corona.īack in late August of 1997, the joint Italian-Dutch BeppoSAX X-ray satellite caught Medusa's head having a bad hair day. The hot B8 dwarf is instead ber eft of an outer convection zone and appears magnetically quiescent. ![]() The consequent rapid rotation of the K star, in concert with its outer convection zone, engenders vigorous and violent magnetic activity. The stars are tidally-locked, and both rotate with the same period as their orbit, much like the Moon is tidally-locked to its orbit about the Earth. When the fainter K star passes in front of the brighter B star, Algol dims significantly - behaviour thought of as somewhat spooky long before its binary nature was known. ![]() ![]() It comprises a B8 dwarf and a K0 subgiant in a 2.86 day orbit. The Arabic name "Algol", of the eclipsing close binary star sometimes known as the Demon Star, derives from the "head of the ghoul" -in Greek tradition the head of the venomous snake-haired Medusa severed by the demigod fellow Perseus.
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