Dusty spiral around a red star may explain end of Sun’s life

Astronomers have discovered a never-before-seen spiral structure around a dying red giant star about 1,000 light-years from Earth that may offer a preview of how the Sun will be at the end of its life.

Using the Atacama Large Millimeter/Submillimeter Array (ALMA) in northern Chile, an international team of astronomers found the spiral structure in the envelope of gas and dust around a red giant star and took a detailed three-dimensional reading of its composition, SPACE.com reported.

The spiral is thought to be created from the gases being expelled by the dying red giant called R Sculptoris. It provides information about the velocity of the wind blowing off of R Sculptoris, revealing that the star has expelled three times as much mass as previously estimated.

“We can ‘walk along’ the spiral and use it as a clock to see what happened when,” said Matthias Maercker, of Germany’s University of Bonn.

Low-to intermediate-mass stars like the sun expand into red giants during the last stages of their evolution. When the sun reaches this stage in about 5 billion years, its outer layer will spread as far as Earth’s orbit.

Every 10,000 to 50,000 years, these gaseous giants burn helium for a few hundred years in a runaway process known as a thermal pulse, causing the layers of the star to mix.

“Thermal elements are an essential part of late stellar evolution,” Matthias Maercker told SPACE.com in an email.

“They are responsible for the formation of new elements, which eventually will get incorporated into new stars and planets,” Matthias Maercker said.

By studying the corkscrewed expulsion from R Sculptoris, the astronomers calculated that the star was shedding more mass during thermal pulses than had been estimated.

“This means that much more mass is lost during a time where new elements cannot yet be incorporated into the wind.

Hence it will take longer for these elements to be blown into space – most likely, only during the next pulse,” Matthias Maercker said.

The spiral shape was caused by a companion star pushing through the layers expelled by T Sculptoris. The formation is allowing the scientists to study the history of the thermal pulses: Elements blown off at higher speeds create more widely separated spirals, while phases of slower mass loss are more tightly packed.

Located in the constellation Sculptor in the Southern Hemisphere, R Sculptoris is a typical red giant, so its evolution could provide a hint of what to expect from the Sun down the road, astronomers believe.

The research was published in the journal Nature.

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