Australian astronomers have helped investigate the gassy remains of an ancient star and found that its “messy death” also killed an “innocent bystander” star.

December 9, 2022

Australian astronomers investigating the “messy death” of an ancient star have found the gassy remains of an “innocent bystander”.

The star, which was nearly three times the size of the Sun, spewed out clouds of gas about 2500 years ago, forming the Southern Ring Nebula, Macquarie University researchers say.

They’re part of an international team of scientists who have been studying James Webb Space Telescope images of the nebula in a bid to determine how the star from which it formed died.

“It created shrouds of gas that have expanded out from the ejection site, and left a remnant dense white dwarf star, with about half the mass of the Sun, but approximately the size of the Earth,” astrophysicist Orsola De Marco said on Friday.

“We were surprised to find evidence of two or three companion stars that probably hastened its death, as well as one more innocent bystander star that got caught up in the interaction.”

About 70 astronomers from more than 60 organisations across Europe, North, South and Central America and Asia developed theories and models about how the star died.

They found an ultra-hot white dwarf star that had burned up its hydrogen at the centre of the nebula, which is a giant cloud of dust and gas in space that can from after a dying star explodes, according to NASA.

“This star is now small and hot, but is surrounded by cool dust,” Joel Kastner, an astronomer from the Rochester Institute of Technology USA involved in the study, said.

“We think all that gas and dust we see thrown all over the place must have come from that one star, but it was tossed in very specific directions by the companion stars.”

Researchers also identified a series of spiral structures moving out from the centre, that they believe were created by a companion star orbiting the now dead central star as it lost its mass.

The images also revealed jets of gas and matter that had shot out from the nebula in different directions, implying “a triple star interaction at the centre”.

“We first inferred the presence of a close companion because of the dusty disk around the central star,” Prof De Marco said.

“Once we saw the jets, we knew there had to be another star or even two involved at the centre”

The team believes there were likely to have been three or four companion stars around the the central star at varying distances from it.

“If this is the case, there are four or even five objects involved in this messy death,” Prof De Marco said

The study was based on James Webb Space Telescope images, along with data from the European Southern Observatory Very Large Telescope in Chile, the San Pedro de Martir Telescope in Mexico, the Gaiaace Telescope, and the Hubble Space Telescope.

It paves the way for future observations of nebulae that have the potential to provide insights into astrophysical processes, including colliding winds, binary star interactions, supernovae and gravitational wave systems.

The study was published in Nature Astronomy on Friday.