It is always nice to gather real data rather than rely on the best
guess theory can produce. This is a star in its last stages of
active life with most of the hydrogen long gone. It leaves quite a
signature that will also be dissipated in a relatively short time.
It is a nice addition to our knowledge of a star's life progress.
Strange Star Spiral
Offers Clues to Sun's Fate
by Nola Taylor Redd,
SPACE.com Contributor
An intriguing spiral
structure surrounding a pulsing red giant star may be offering a
preview of how the sun will behave 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, one
never seen before, in the envelope of gas and dust around a red giant
about 1,000 light-years from Earth and took a detailed
three-dimensional reading of its composition.
The spiral is thought
to be created from the gases being expelled by the dying red
giant called R Sculptoris. The structure 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. [Weird
Spiral Around Red Giant Star (Video)]
Thermal pulsing
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 behemoths 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," 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."
These new elements
take time to reach the outer layers of the star. 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," Maercker said. "Hence it will
take longer for these elements to be blown into space ― most
likely, only during the next pulse."
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. The intensity of the spiral reveals how
much mass was lost in each phase.
"Now that the
companion star causes the spiral structure in the stellar wind from R
Sculptoris, we can see it and, in a very detailed way, measure how it
has evolved since the last thermal pulse," Maercker said.
The research was
published in today's (Oct. 10) online version of the journal Nature.
ALMA and the star
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.
ALMA is a new network
of 66 radio dishes linked together to observe cooperatively. The
facility won't be fully operational before next year; fewer than half
of the telescopes in the array were functional when R Sculptoris was
examined.
Maercker and his team
hope to use ALMA's full array to get an even closer look at R
Sculptoris in the future. "We hope to see exactly where the
spiral begins," he said.
That information
should reveal the mass and orbits of R Sculptoris and its companion
star, providing more exact information about what happens to red
giants during and after their thermal pulses.
"This will allow
us to understand late stellar evolution better, and where
and how the material for new stars is created," Maercker said.
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