The stunning filaments and coils of light that make up the Southern Ring Nebula were sculpted by up to five stars, all orbiting each other in a complex dance
January 20, 2023
The Southern Ring Nebula is full of stars. Nebulae, huge clouds of gas and debris in space, were once thought to have resulted from the death of a single star, but the swoops and twists of this one were formed by at least four orbiting stars — maybe even five.
Orsola De Marco of Macquarie University in Australia and her colleagues viewed the nebula, also known as NGC 3132, with the James Webb Space Telescope (JWST) and created a three-dimensional model to find out its internal structure. “Ideally, you would find the companion stars and rewind time. In practice, that’s not possible, so you have to work like a crime scene investigator, where the fog itself tells what happened to it,” says De Marco.
When a star the size of the Sun dies, it sheds its outer layers, and the core of the star that remains at the center heats them and causes them to 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 distant.
The JWST images revealed a disk of dust around the primary star, which must be caused by an additional companion star orbiting even closer than the one we know of — about the distance between Earth and the Sun. We see no sign of the star itself, so it may have fallen in and merged with the primary star.
The nebula’s outer edges also show a series of arcs that look a bit like the rings in a tree stump. The spacing of these rings allowed researchers to calculate the distance between the primary star and the star that carved it into the expanding cloud of gas, which must be 40 to 60 times more distant than the star that created the dust disk .
“Every time we’ve had rings like this, the only explanation that really worked was that there’s a companion around the star as the star falls away, and as it orbits it imprints a trail in the material,” says De Marco. “You need a mate to make the rings, but it can’t be the same mate that made the disc.”
Eventually, the 3D model of the nebula revealed evidence of a possible fifth star. The reconstruction looks a bit like a lumpy egg, and each bump is paired with another on the opposite side of the gas cloud. These clumps are most likely formed by jets from the central star, but the only way to give them the random orientation they appear to be would be through the chaotic orbits of three nearby stars. That would require an additional star orbiting the primary star and the extremely close star that created the dust disk, making the Southern Ring a quintet of stars.
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