The dying red giant star – V Hydrae stuns astrophysicists with a series of expanding rings

V Hydrae (a.k.a V Hya) is a carbon star 1,300 light-years from Earth in the constellation Hydra. Astrophysicists studying the red giant star witnessed the carbon-rich star expel six slowly expanding molecular rings and an hour glass structure ejecting matter into space at high speeds.

Researchers from NASA’s Jet propulsion labs and UCLA studying the dying star believe the star is undergoing rapid evolution before the energy production shuts down.

The study, was conducted using the Atacama Large Millimeter/submillimeter Array, known as ALMA, and data from the Hubble Space Telescope, the results were published in the Astrophysical Journal.

V Hydrae belongs to a group of stars known as asymptotic giant branch stars (AGB stars), 90% of stars with masses equal to or exceeding the Sun evolve into AGB stars. The astronomers are interested in V Hydrae because of its large plasma eruptions that occur every eight years. They believe a companion star which is almost invisible contributes to this peculiar behaviour of V Hydrae.

Mark Morris, a UCLA professor of physics and astronomy and a co-author of the study noted “This is the first and only time that a series of expanding rings has been seen around a star that is in its death throes — a series of expanding ‘smoke rings’ that we have calculated are being blown every few hundred years.” While a dying star shedding its atmosphere and eventually most of its mass is seen with most late-stage red giant stars but matter being expelled as a series of rings have baffled researchers. He added that the mechanism that produces the rings is unknown and will require further investigation.

“We suspect that it might be related to the presence of orbiting companion stars, but it is difficult to explain that given the few-hundred-year interval between ring ejections,” Morris said. “This star is providing a new and fascinating wrinkle to our understanding of how stars end their lives.”

Astronomer at JPL and the study’s lead author, Raghvendra Sahai, believes the research indicates that previous assumptions about star deaths may be wrong. “Our study dramatically reveals that the traditional model of how AGB stars die — through the mass ejection of fuel via a slow, relatively steady, spherical wind over 100,000 years or more — is at best, incomplete, or at worst, incorrect,” he said.

Researchers call the the six rings that have expanded outward from V Hya, the DUDE, for Disk Undergoing Dynamical Expansion. The expansion took over the course of roughly 2,100 years forming a warped, disk-like structure, around the star.

Sahai believes the researchers got lucky with V Hydrae as the transistion phase that dying stars go through towards the end of their lives does not last long and therefore making it very difficult to observe and study them.

Researchers also found an hourglass-shaped structure centered on the star and oriented perpendicularly to the disk. The two lobes of the hourglass have been shaped by a directed, fast wind that is blowing in two opposite directions at speeds up to 500,000 miles per hour.

Sahai said. “V Hydrae has impressed us with its multiple rings and acts, and because our own sun may one day experience a similar fate, it has us at rapt attention.”