The glorious, billowing Southern Ring Nebula is the cocoon of a dying star, and it has a secret. Scientists have found that this nebula has a double ring structure that shows 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 far away in the constellation of Vela, the Veles. The name “planetary nebula“it’s a misnomer: these nebulae have nothing to do with each other planets. Instead, they are the final exhalations of death, ground-I like stars, which transform inside the nebulous chrysalis until it finally blossoms into a white dwarf. A nebula forms from the outer envelope of the dying star, which swells space following that of the star red giant phase
The Southern Ring Nebula was photographed in December 2022 by the James Webb Space Telescope (JWST), which revealed molecular hydrogen gas forming the nebula’s “exoskeleton.” It refers to warm gas that radiates with a temperature equal to about 1,000 kelvin (1,340 degrees Fahrenheit, or 726 degrees Celsius) as it is illuminated and heated by ultraviolet light from the white dwarf same This exoskeleton, however, represents only a small fraction of the nebula’s molecular gas.
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A team led by Joel Kastner of the Rochester Institute of Technology went looking for more molecular gas in the nebula, specifically looking for carbon monoxide gas using the Submillimeter Array (SMA), which is a group of eight radio telescopes in an inactive volcano called Mauna. Kea in Hawaii. Carbon monoxide mixes with hydrogen and other molecular gases within the nebula, so looking at the carbon monoxide content is actually a proxy for looking at all those other molecules that aren’t so easy to detect. Indeed, the SMA was able to measure both the distribution and the speeds of the carbon monoxide molecules, showing which parts are moving towards us and which are moving away from us.
“JWST showed us the hydrogen molecules and how they stack up in the sky, while the Submillimeter Array shows us carbon monoxide that is colder than can be seen in the JWST image,” Kastner said in a press release.
As the name of the southern ring suggests, it is primarily shaped (from our point of view) as a ring. SMA observations showed that this ring is expanding, which is to be expected as the nebula slowly grows before dispersing. However, the data also allowed Kastner’s team to create a three-dimensional map of the nebula’s molecular exoskeleton. This offered a surprise. Not only were the researchers able to show that what we see as a ring is just one lobe of a bipolar nebula seen at the end, but they also found a second ring perpendicular to the first.
“When we started going around the whole nebula in 3D, we immediately saw that it was indeed a ring, and then we were surprised to see that there was another ring,” Kastner said.
The whole strange arrangement paints a fascinating tail of not one, not even two, but quite possibly three stars at the heart of the nebula. Only one of these stars, the most massive of the three, will have reached the end of its life, but the stellar trio, if all three actually exist, is likely to be too close to each other or too weak to resolve separately, even. by JWST.
There is growing evidence that some planetary nebulae, at least those with complex structures, form from the interference of a companion star with the dying central star. For the southern ring, Kastner’s team posits that a triple system formed from a closure binary is orbited by a third more distant star within an orbital radius of 60 astronomical units of the binary (an astronomical unit, AU, is the distance between land and the sun, and in ours solar system 60 AU would be out at the far end of the Kuiper belt).
The two lobes of the Southern Ring have a narrow or “pinched” waist, like an hourglass, which is a common feature of planetary nebulae emanating from a binary star system in which one of the stars is arriving at the end of his life. The binary companion is able to gather the material shed by the dying star so that it escapes in a polar, rather than equatorial, direction, forming the two lobes. Mid-infrared observations from JWST support this hypothesis, finding an excess of infrared light from the central star system, which is a classic signature of a dusty disk formed by interactions between the red giant and a binary companion close.
So that explains the first ring. The origin of the second ring, the team says, is less certain.
Although the southern ring appears bilobed, some material must have been emitted as a roughly spherical or ellipsoidal envelope of material ejected from the red giant, a rapid mass-loss event that may have represented its final exhalation of material to leave the white behind. dwarf The binary star system produces a series of fast, tight jets, but if there is a third star, then the additional star gravity it would act on the inner binary, causing the direction of the jets to “babble”, like a breastplate. These earlier jets would have cut a circular gap in the ellipsoidal component of the nebula, thus creating the second ring.
Kastner stresses that this explanation is still speculative, but the nebula’s central ionized cavity has evidence of such jets in its structure.
Other ring-shaped planetary nebulae, such as the Helix Nebula (NGC 7293 in Aquarius), have also been shown to have bilobed structures whereby we look “down” the end of one lobe. The discovery of the second ring in the Southern Ring Nebula, or should that now be the Southern Rings, plural? — is prompting astronomers to check some of these other known ring nebulae to see if they’ve also lost second rings.
Planetary nebulae don’t just mean stellar death. They also hold the promise of new life, literally, in a sense.
“Where carbon, oxygen and nitrogen come in the universe “Come?” asks Kastner. “We’re seeing it generated in sun-like stars that are dying, like the star that just died and created the Southern Ring.”
As an expanding planetary nebula disperses interstellar spaceit spreads these molecules through the cosmos, where they end up in giant molecular clouds that form the next generation of stars and planets.
“Much of this molecular gas would end up in planetary atmospheres, and atmospheres can support life,” says Kastner. In fact, all elements on Earth heavier than hydrogen and helium originated inside stars and were then ejected into space when those stars died.
We are literally a star, as many experts like to say.
So when we marvel at the beauty of stellar death in nebulae like the Southern Ring, we can also imagine it as a stellar phoenix that will one day rise from the ashes and begin the cycle of birth and death of the stars again. To quote Battlestar Galactica, all of this has happened before, and all of this will happen again.
The findings were published on April 2 a Astrophysics Magazine.
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