Strange structure seen around distant star

GARCHING, Germany, Oct. 11 (UPI) -- The spiral structure surrounding a pulsating red giant star seen by a telescope in Chile is the first such structure ever seen around a star, astronomers say. The surprising structure was observed in an envelope of gas and dust surrounding the star R Sculptoris about 1000 light-years from Earth, the European Southern Observatory reported from its headquarters in Garching, Germany. A previously unseen companion star orbiting the red giant has likely created this structure, astronomers say. "We've seen shells around this kind of star before, but this is the first time we've ever seen a spiral of material coming out from a star, together with a surrounding shell," ESO scientist Matthias Maercker said. Late in their lives, stars with masses up to eight times that of the Sun become red giants and lose a large amount of their mass in a dense stellar wind while periodically undergoing thermal pulses. These are short-lived phases of explosive helium burning in a shell around the stellar core resulting in the formation of a large shell of dust and gas around the star. Thermal pulses occur approximately every 10,000 to 50,000 years and last only a few hundred years, astronomers said. The new observations of R Sculptoris show it experienced a thermal pulse event about 1,800 years ago that lasted for about 200 years, with the companion star shaping the cosmic wind from the red giant into a spiral structure.