A strange and completely unexpected spiral structure has been observed in the material around the old star R Sculptoris, by the Atacama Large Millimeter/submillimeter Array (ALMA).
This is the only time that a structure like this has been seen around an old red giant — a spherically shaped shell covers the outer regions of the structure.
This is also the first time that researchers have gotten full three-dimensional information about such a spiral. “The strange shape was probably created by a hidden companion star orbiting the red giant,” a statement from the European Southern Observatory noted.
The researchers involved sighted the “surprising spiral structure” in the gas surrounding the red giant star R Sculptoris. “This means that there is probably a previously unseen companion star orbiting the star. The astronomers were also surprised to find that far more material than expected had been ejected by the red giant.”
“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,” said the lead author on the paper presenting the results, Matthias Maercker (ESO and Argelander Institute for Astronomy, University of Bonn, Germany).
The European Southern Observatory added: “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.
“Even in the Early Science phase, when the new observations were made, ALMA greatly outperformed other submillimetre observatories. Earlier observations had clearly shown a spherical shell around R Sculptoris, but neither the spiral structure nor a companion was found.”
“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,” added Wouter Vlemmings (Chalmers University of Technology, Sweden), a co-author of the study.
Here’s more from the European Southern Observatory
“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. During the red giant stage stars also periodically undergo thermal pulses. These are short-lived phases of explosive helium burning in a shell around the stellar core. A thermal pulse leads to material being blown off the surface of the star at a much higher rate, resulting in the formation of a large shell of dust and gas around the star. After the pulse the rate at which the star loses mass falls again to its normal value.
“Thermal pulses occur approximately every 10,000 to 50,000 years, and last only a few hundred years. The new observations of R Sculptoris show that it suffered a thermal pulse event about 1800 years ago that lasted for about 200 years. The companion star shaped the wind from R Sculptoris into a spiral structure.”
“By taking advantage of the power of ALMA to see fine details, we can understand much better what happens to the star before, during and after the thermal pulse, by studying how the shell and the spiral structure are shaped,” says Maercker. “We always expected ALMA to provide us with a new view of the Universe, but to be discovering unexpected new things already, with one of the first sets of observations is truly exciting.”
“It’s a real challenge to describe theoretically all the observed details coming from ALMA, but our computer models show that we really are on the right track. ALMA is giving us new insight into what’s happening in these stars and what might happen to the Sun in a few billion years from now,” says Shazrene Mohamed (Argelander Institute for Astronomy, Bonn, Germany and South African Astronomical Observatory), a co-author of the study.
“In the near future, observations of stars like R Sculptoris with ALMA will help us to understand how the elements we are made up of reached places like Earth. They also give us a hint of what our own star’s far future might be like,” concludes Matthias Maercker.
This research is being published this week in the journal Nature.
Source: European Southern Observatory
Image Credits: ALMA (ESO/NAOJ/NRAO); ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin