Chalmers: Alma telescope discovering the unexpected

Astronomers have discovered a totally unexpected spiral structure in space. The strange shape, discovered in gas and dust surrounding the red giant star R Sculptoris, was probably created by a hidden companion star orbiting the star. The research, which appears in the journal Nature this week, gives new insight on how stars like the Sun return material to space when they become old.

The discovery was made by an international team of astronomers, among them several scientists from Chalmers University of Technology and Onsala Space Observatory. The team used the Atacama Large Millimeter/submillimeter Array (Alma), the most powerful millimetre/submillimetre telescope in the world.

The surprising spiral structure was discovered in the gas around the red giant star R Sculptoris . This is the first time that such a structure, along with an outer spherical shell, has been found around a red giant star. It is also the first time that astronomers could get full three-dimensional information about such a spiral.

The presence of the spiral means that there is probably a previously unseen companion star orbiting the star.

“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,” says Matthias Maercker, the lead author on the paper presenting the results, and astronomer at ESO and the Argelander Institute for Astronomy, University of Bonn, Germany.

Because they blow out large amounts of material, red giants like R Sculptoris are major contributors to the dust and gas that provide the bulk of the raw materials for the formation of future generations of stars, planetary systems and subsequently for life. The astronomers were surprised to find that far more material than expected had been ejected by the red giant.

"When we observed the star with Alma, not even half its antennas were in place. It's really exciting to imagine what the full Alma array will be able to do once it's completed in 2013," says Wouter Vlemmings, a co-author of the study and astronomer at Chalmers and Onsala Space Observatory.