October 10, 2012
Spiral Structure Sits Around Old Star R Sculptoris
[ Watch the Video: Slicing Through View of the Material Around R Sculptoris ]
Lee Rannals for redOrbit.com - Your Universe Online
Astronomers have discovered an unexpected spiral structure in the material around an old star called R Sculptoris
The team used the Atacama Large Millimeter/submillimeter Array (ALMA) to discover the surprising spiral structure in the gas around the red giant star, which could mean there is 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,” said lead author on the paper, Matthias Maercker.
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.
When new observations were made, ALMA outperformed other submillimeter observatories. Earlier observations had shown a spherical shell around R Sculptoris.
"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," said Wouter Vlemmings, a co-author of the study.
Stars with masses up to eight times that of the Sun become red giants later on, and lose a large amount of their mass in a stellar wind. During this stage, the stars periodically undergo thermal pulses.
These phases of explosive helium burning in a shell around the stellar core are short lived. A thermal pulse leads to material being blown off the surface of the star, resulting in a large shell of dust and gas around the star.
Thermal pulses occur about every 10,000 to 50,000 years, and last only a few hundred years.
“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,” Maercker said. “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.”
The team of astronomers also performed computer simulations to follow the evolution of a binary system in order to describe the observed structure around R Sculptoris.
"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," said Shazrene Mohamed, a co-author of the study.
The researchers reported their findings in the journal Nature this week.