The amazing filaments and spirals of light that make up the Southern Ring Nebula were formed by up to five stars, all orbiting each other in a complex dance.
20 January 2023
The Southern Ring Nebula is full of stars. Nebulae, huge clouds of gas and debris in space, were once thought to be created from the death of a single star, but the swirls and eddies of this one were made up of at least four stars orbiting each other, such sometimes even five.
Orsola De Marco of Macquarie University in Australia and her colleagues viewed the nebula, also called NGC 3132, using the James Webb Space Telescope (JWST), and created a three-dimensional model to discover its internal structure. “The ideal would be to find the companion stars and go back in time. In practice, you can’t do that, so you have to work like an investigator at a crime scene where the nebula itself tells you what happened to it,” says De Marco.
When a sun-sized star dies, it sheds its outer layers and the stellar core left in the middle heats them up and makes them shine. Before these new images, we knew there were two other stars orbiting the main star that created the Southern Ring Nebula, one close and one distant.
The JWST images revealed a disk of dust around the main star that must be caused by an additional companion star, orbiting even closer than we knew, roughly the distance between Earth and the sun. We see no sign of the star itself, so it may have fallen and merged with the parent star.
The outer edges of the nebula also show a series of arcs that look a bit like rings on a tree stump. The spacing of these rings allowed the researchers to calculate the distance between the primary star and the star that sculpted them into the expanding cloud of gas, which must be 40 to 60 times more distant than the star that created the dusty disk.
“Whenever we’ve had rings like this, the only explanation that really works is that there’s a companion around the star when the star is breaking away, and as it orbits it leaves an imprint in the material,” De Marco says. “You need a partner to make the rings, but it can’t be the same partner that made the record.”
Finally, the 3D model of the nebula revealed evidence of what could be a fifth star. The reconstruction looks a bit like a lumpy egg, with each bulge paired with another on the opposite side of the gas cloud. These bulges are most likely formed by jets from the central star, but the only way to give them the random orientations they seem to have would be through the chaotic orbits of three nearby stars. That would require an additional star in orbit around the main star and the extremely close one that formed the dusty disk, making the Southern Ring a stellar quintet.
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