'We were amazed': Scientists find hidden structure in nebula captured by James Webb telescope

The glorious, billowing Southern Ring Nebula is the cocoon of a dying star — and it has a secret. Scientists have found this nebula to exhibit a double-ring structure that evidences not one, but possibly three stars at its heart.

The Southern Ring Nebula, also designated NGC 3132, is a planetary nebula located about 2,000 light-years away in the constellation of Vela, the Sails. The name "planetary nebula" is a misnomer — such nebulas have nothing to do with planets. Instead, they are the final exhalations of dying, sun-like stars, which transform inside the nebulous chrysalis until finally blossoming into a white dwarf. A nebula is formed from the dying star's outer envelope, which is puffed off into space following the star's red giant phase.

The Southern Ring Nebula was imaged in December 2022 by the James Webb Space Telescope (JWST), which revealed molecular hydrogen gas forming the nebula's "exoskeleton." This refers to warm gas radiating with a temperature equal to about 1,000 kelvin (1,340 degrees Fahrenheit, or 726 degrees Celsius) as it gets illuminated and heated by ultraviolet light coming from the white dwarf itself. That exoskeleton, however, only represents a small fraction of the molecular gas in the nebula.

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A team led by Joel Kastner of the Rochester Institute of Technology went hunting for more of the nebula's molecular gas, specifically searching for carbon monoxide gas using the Submillimeter Array (SMA), which is a group of eight radio telescopes on an inactive volcano named Mauna Kea in Hawaii. Carbon monoxide is mixed in with hydrogen and other molecular gases inside the nebula, so observing the carbon monoxide content is actually a proxy for observing all those other molecules that are not as easy to detect. Sure enough, the SMA was able to measure both the distribution and velocities of the carbon monoxide molecules, showing which parts are moving towards us and which are moving away from us.

"JWST showed us the molecules of hydrogen and how they stack up in the sky, while the Submillimeter Array shows us the carbon monoxide that is colder that you can't see in the JWST image," said Kastner in a press statement.

As the Southern Ring's name suggests, it is primarily shaped (from our point of view) as a ring. The SMA observations showed that this ring is expanding, which is to be expected as the nebula slowly grows before eventually dispersing. However, the data also allowed Kastner's team to create a three-dimensional map of the nebula's molecular exoskeleton. This offered up a surprise. Not only were the researchers able to show that what we see as a ring is merely a lobe in a bi-polar nebula seen end-on, but they also found a second ring perpendicular to the first.