James Webb Space Telescope’s iconic image reveals a stellar surprise

The Southern Ring Nebula is more complex than first appears.

 

Astronomers felt that the Southern Ring Nebula was rather ordinary. Until they saw it through the eyes of the James Webb Space Telescope. (Photo Credit: NASA, ESA, CSA, and STScI)

 

When scientists first viewed breathtaking images of the Southern Ring Nebula collected by the James Webb Space Telescope, they realized they would have to reassess what they thought they knew about the unimpressive object.

Located about 2,000 light-years away from Earth in the constellation Vela, which is visible in the southern sky, the Southern Ring Nebula was among the James Webb Space Telescope’s early science targets, and a portrait was among the photos initially given to the world in July. The Webb Space Telescope’s predecessor, the Hubble Space Telescope, had already captured images of the nebula, also known as NGC 3132. But Hubble’s photos, while magnificent, failed to capture the whole reality of this dust cloud, which sprung up from an implosion of a dead star around the size of the sun barely 2,500 years ago.

“The Southern Ring Nebula was never regarded especially exceptional,” Orsola De Marco, an astrophysicist at Macquarie University in Australia and a primary author of new research investigating Webb’s photos, told Space.com. “The nebula was renowned for having an extensive envelope and for containing two visible stars orbiting each other.”

Despite its name, the Southern Ring Nebula, a so-called planetary nebula, has nothing to do with planets and was created when a red giant star collapsed. A red giant, which can be hundreds of times wider than the original star, forms when a star about the size of the sun runs out of hydrogen fuel in its core. The nebula is created when the red giant eventually sheds its outer layers, after which it compresses into white dwarf-like cooling remains.

The white dwarf may be seen as a minuscule speck of light at the middle of the ring in Hubble photos, outshone by a much brighter companion star that is located 1,300 sun-Earth distances away. The shed layers form a relatively smooth ring-shaped cloud.

Webb offered a more sophisticated image of the nebula. The Near Infrared Camera (NIRCam), which detects hot objects like stars, and the Mid-Infrared Instrument (MIRI), which excels at detecting dust, are two of the pieces of equipment used by the telescope of the century to image the cloud.

It was MIRI’s view that immediately piqued the astronomers’ curiosity. Instead of the one enormous and one tiny star knew from Hubble’s view, two stars of equal proportions emerged. And surprisingly, the star that the astronomers recognized as a white dwarf was unexpectedly red.

White dwarfs are hot and don’t shine in this wavelength, according to De Marco. Therefore, we realized right away that the white dwarf must be covered in a large disk of cool dust.

 

One of the center stars in the Southern Ring Nebula is unusually red, as shown in an image taken by the James Webb Space Telescope’s MIRI instrument. (Photo Credit: STScI, NASA, ESA, CSA)

 

Immediately the astronomers pondered how the dust disk came into being. Such disks are frequently composed of material from a smaller star orbiting a more massive star, whose gravity disrupts the companion. However, the white dwarf’s known luminous companion was too far away to be impacted by it, was located in the Southern Ring Nebula’s core. The only plausible conclusion, De Marco argued, was that another, the undetectable tiny star was orbiting the white dwarf much closer in, spewing the dust. The two-star system abruptly changed into a three-star system.

But the surprises didn’t end there.

Under Webb’s piercing scrutiny, the comparatively flat surface of the ring-shaped cloud viewed by Hubble changed into a maelstrom of churning streams and dust filaments. One characteristic really drew the scientists’ eyes: concentric layers extending outward toward the ring’s edges like ripples in a pond. Astronomers have seen such concentric shells before, including in Webb’s photos of the nebula surrounding a big star known as WR140.

 

Concentric ripples may be seen in the ring-shaped cloud in a NIRCam image of the Southern Ring Nebula. (Photo Credit: STScI, NASA, ESA, CSA)

 

“There are several nebulas with arches like that,” De Marco remarked. “A lot of modeling has been done to try to understand where [the arches come from], but the only model that works is that you have an orbiting companion, and when the star ejects the nebula, the nebula streams past the orbiting companion, acting like a sprinkler and creating a spiral that is ingrained into the expanding nebula.”

By calculating the distance between the concentric rings, astronomers can learn a lot about the companion star that generated the formations, De Marco continued, including its distance from the white dwarf whose ejected envelope created the nebula. The distance calculation revealed that neither of the two partners, the visible one and the one responsible for the dusty disk, could have generated the ripples. A third star, somewhere in between the two, was inserted into the system.

 

Hubble’s picture of the Southern Ring Nebula was far less interesting. (Photo Credit: NASA)

 

Everyone had been uninterested in the uninteresting nebula until it suddenly became considerably more intriguing. Further examinations of the nebula’s form even suggested that a fifth star might be concealed within the dusty disk near the white dwarf, so the story wasn’t quite done.

One of the study’s co-authors, astronomer Joel Kastner of the Rochester Institute of Technology in New York, said: “We think all that gas and dust we see thrown all over the place [in the Southern Ring Nebula] must have come from that one star, but it was tossed in very specific directions by the companion stars.”

The unanticipated discovery of the obscure stars demonstrates how effective Webb is at revealing the mysteries of our universe.

The study is detailed in a report that was released on Thursday, December 8 in the journal Nature Astronomy.

Source: space.com

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