Hidden companion likely caused spiral shell around red giant

New Scientist : It isn’t unusual to find a red giant surrounded by concentric spherical shells of gas and dust. R Sculptoris ejects material to form such shells every 10000 to 50000 years. However, its emissions form a spiral, not concentric circles. The unusual pattern appears to be caused by an unseen star orbiting the red giant. The spiral structure of the system was revealed by the Atacama Large Millimeter/Submillimeter Array. ALMA, only half constructed, will be the most powerful telescope that focuses on wavelengths between IR and microwave when completed in March 2013.