The dazzling filaments and coils of light that make up the Southern Ring Nebula were shaped by as many as five stars, all orbiting each other in an intricate dance.
January 20, 2023
The Southern Ring Nebula is full of stars. It was once thought that nebulae, huge clouds of gas and debris in space, were created from the death of a single star, but the curves and spirals of this one were formed by at least four stars orbiting each other – maybe as many as 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. “Ideally, you would find the companion stars and go back in time. In practice, you can’t do that, so you have to work as an investigator at the crime scene, where Nebula herself is telling what happened to her,” says De Marco.
When a star the size of the Sun dies, it loses its outer layers and the stellar core left in the middle heats them up and makes them glow. Prior to these new images, we knew that there were two other stars orbiting the main star that created the Southern Ring Nebula, one nearby and one far away.
The JWST images revealed a dusty disk around the primary star that must be caused by an additional companion star, orbiting even closer than what we knew – the distance between Earth and the Sun. We don’t see any signs of the star itself, so it could have fallen and merged with the primary star.
The nebula’s outer edges also show a series of arcs that look a bit like the 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 carved them out of the expanding gas cloud, which must be 40 to 60 times farther away than the star that created the dusty disk.
“Every time we’ve had rings like this one, 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 a trail in the material,” says De Marco. “You need a partner to make the rings, but it can’t be the same partner who made the puck.”
Finally, the 3D model of the nebula revealed evidence of what might be a fifth star. The reconstruction looks a bit like a bumpy egg, and each bulge is paired with one on the opposite side of the gas cloud. These chunks are likely formed by jets from the central star, but the only way to give them the random orientations they appear to have would be through the chaotic orbits of three nearby stars. That would require an additional star orbiting the primary star and the extremely close one that formed the dust disk, making the Southern Ring a stellar quintet.
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