At least three, and possibly four, progenitor stars crafted the oblong, curvy shapes of the Southern Ring Nebula, according to a new analysis of data from the NASA/ESA/CSA James Webb Space Telescope.
This image of the Southern Ring Nebula was captured by Webb’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI); it highlights the very hot gas that surrounds the central stars. Image credit: NASA / ESA / CSA / STScI / O. De Marco, Macquarie University / J. DePasquale, STScI.
The Southern Ring Nebula, also known as NGC 3132, the Eight-Burst nebula, and Caldwell 74, is located some 2,500 light-years away in the constellation of Vela.
Composed of gas and dust, this planetary nebula has a diameter of about 0.5 light-years.
The Southern Ring Nebula has long been known to harbor a visual binary system comprising the central (progenitor) star and a companion star.
The new Webb images contain multiple, new lines of evidence that the nebula is the recent product of a hierarchical multiple progenitor stellar system.
“The central progenitor star was nearly three times the size of our Sun, but much younger, about 500 million years old,” said Macquarie University’s Professor Orsola De Marco.
“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.”
“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.”
This image of the Southern Ring Nebula was captured by Webb’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI); it traces the star’s scattered outflows that have reached farther into the cosmos; most of the molecular gas that lies outside the band of cooler gas is also cold; it is also far clumpier, consisting of dense knots of molecular gas that form a halo around the central stars. Image credit: NASA / ESA / CSA / STScI / O. De Marco, Macquarie University / J. DePasquale, STScI.
For their study, the astronomers also used the data from ESO’s Very Large Telescope, the San Pedro de Mártir Telescope, ESA’s Gaia satellite, and the NASA/ESA Hubble Space Telescope.
“When we first saw the images, we knew we had to do something, we must investigate,” Professor De Marco said.
“The community came together and from this one image of a randomly chosen nebula we were able to discern much more precise structures than ever before. The promise of Webb is incredible.”
Shining at the center of the Southern Ring Nebula is an ultra-hot central star, a white dwarf that has burned up its hydrogen.
“This star is now small and hot, but is surrounded by cool dust,” said Dr. Joel Kastner, an astronomer at the Rochester Institute of Technology.
“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.”
Examine the straight, brightly-lit lines that pierce through the rings of gas and dust around the edges of the Southern Ring Nebula in Webb’s image; these ‘spokes’ appear to emanate from one or both of the central stars, marking where light streams through holes in the nebula. Image credit: NASA / ESA / CSA / STScI / O. De Marco, Macquarie University / J. DePasquale, STScI.
There are also a series of spiral structures moving out from the nebula’s center.
These concentric arches would be created when a companion orbits the central star while it is losing mass.
Another companion is further out and is also visible in the picture.
Looking at a 3D reconstruction of the data, the authors also saw pairs of protuberances that may occur when astronomical objects eject matter in jet form.
These are irregular and shoot out in different directions, possibly implying a triple star interaction at the center.
“We first inferred the presence of a close companion because of the dusty disk around the central star, the further partner that created the arches and the super far companion that you can see in the image,” Professor De Marco said.
“Once we saw the jets, we knew there had to be another star or even two involved at the center, so we believe there are one or two very close companions, an additional one at middle distance and one very far away.”
The results were published in the journal Nature Astronomy.
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O. De Marco et al. The messy death of a multiple star system and the resulting planetary nebula as observed by JWST. Nat Astron, published online December 8, 2022; doi: 10.1038/s41550-022-01845-2
