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JWST Delivers Insights Into How The Southern Nebula Was Carved

Astronomers think that at least four stars created this stunning object.

author

Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockDec 8 2022, 16:00 UTC
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The image is split down the middle, showing two views of the Southern Ring Nebula. Both feature black backgrounds speckled with tiny bright stars and distant galaxies. Both show the planetary nebula as a misshapen oval that is slightly angled from top left to bottom right and takes up the majority of each image. At left, the near-infrared image shows a bright white star at the center with long diffraction spikes. Large, transparent teal and orange ovals, which are shells ejected by the unseen central star, surround it. At right, the mid-infrared image shows two stars at the center very close to one another. The one at left is red, the smaller one at right is light blue. The blue star has tiny triangles around it. A large transparent red oval surrounds the central stars. From that extend shells in a mix of colors, which are red to the left and right and teal to the top and bottom. Overall, the oval shape of the planetary nebula appears slightly smaller than the one seen at left.
Near-Infrared and Mid-Infrared views of the Souther Ring Nebula. Image Credit: NASA, ESA, CSA, and STScI

The Southern Ring Nebula was one of the first science targets of JWST. The celestial object is a planetary nebula, created by the release of material from a red giant as it turns into a white dwarf – but a new analysis suggests that is not the whole story. Astronomers now believe that there are more players involved: At least four stars might be behind the structure we see.

The nebula is about 2,000 light-years from Earth. In one of the JWST images, it is possible to see the white dwarf and a companion star. However, there’s more than meets the eye, even with the incredible eye of the latest great space observatory. Two more stars are expected to be around the white dwarf.

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“Technically we did not see them, but we inferred their presence. We only 'see' the main star and the farthest companion - the one that did not really play an active role in the formation of the nebula,” lead author Dr Orsola De Marco from Macquarie University, told IFLScience. “We are however becoming accustomed to the fact that stars 'hunt in packs'!”

Detailed analysis of the near-infrared and mid-infrared observations from JWST suggests that a close companion to the white dwarf is presently hidden by a disk around the central star. Past interactions in this disk are evidence of this unseen star. There are also arches inscribed in the large molecular halo of the nebula, attributed to another hidden companion orbiting this close pair.

“Multiple stellar systems are not rare, particularly as the system is more massive (while 0.5 solar mass stars do not often have companions less massive than themselves, 100 solar mass stars always have MANY companions). We know that for a fact now, so it is not surprising that planetary nebulae central stars are also in multiple systems. When the star evolves it expands into the orbits of the companion(s) and an interaction usually ensues,” Dr De Marco told IFLScience.  

The detailed observations, combined with the models, allow a much clearer understanding of the system, plus a precise estimate of the mass of the progenitor star: about 2.86 times the mass of our Sun.

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These results can be foundational for future JWST work on planetary nebulae as well as other complex systems of wind interactions, such as supernovae and events that produce strong gravitational waves.

The paper is published in the journal Nature Astronomy.


spaceSpace and PhysicsspaceAstronomy
  • tag
  • white dwarf,

  • nebula,

  • stars,

  • JWST,

  • Astronomy,

  • southern ring nebula