The majestic, undulating Southern Rim Nebula is the cocoon of a dying star and has a secret. Scientists found that this nebula has a double-ring structure, proving that it has not one but three stars at its center.
The Southern Ring Nebula, also called NGC 3132, is a planetary nebula located approximately 2,000 km away. light years far away in the constellation Vela, Vela. The name “planetary” nebula” a misnomer; such nebulae planets. Instead, these are the last gasps of death. sun-like stars, they transform inside the nebula chrysalis until they finally collapse into a white dwarf. A nebula forms from the outer shell of the dying star, which inflates outwards. space chasing the star red giant phase.
Southern Ring Nebula in December 2022 James Webb Space Telescope (JWST) revealed the molecular hydrogen gas that forms the “exoskeleton” of the nebula. This means hot gas that radiates at a temperature equal to about 1,000 kelvins (1,340 degrees Fahrenheit or 726 degrees Celsius) when illuminated and heated by ultraviolet light from the atmosphere. white dwarf itself. But this exoskeleton represents only 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 began searching for more of the nebula’s molecular gas; specifically looked for carbon monoxide gas using the Submillimeter Array (SMA), a group of eight radio telescopes located on an inactive volcano called Mauna. Kea in Hawaii. Carbon monoxide is mixed with hydrogen and other molecular gases inside the nebula, so observing the carbon monoxide content is actually a proxy for observing all the other molecules that are not so easy to detect. Indeed, by measuring both the distribution and speed of carbon monoxide molecules, SMA was able to show which fragments were moving towards us and which were moving away from us.
“While JWST shows us hydrogen molecules and how they accumulate in the sky, the Submillimeter Array shows us carbon monoxide, which is so cold that you can’t see it in the JWST image,” Kastner said. press release.
As the name of the Southern Rim suggests, it is essentially shaped like a ring (from our perspective). SMA observations showed that this ring is expanding; This is to be expected as the nebula slowly grows before eventually dissipating. But the data also allowed Kastner’s team to create a three-dimensional map of the nebula’s molecular exoskeleton. This created a surprise. Not only did the researchers show that what we see as a ring is an edge-on lobe of a bipolar nebula, they also found a ring. second ring perpendicular to the first.
“When we started rotating the entire nebula in 3D, we immediately saw that it was indeed a ring, and then we were amazed to see that it was another ring,” Kastner said.
This whole strange arrangement draws a fascinating tail of not one, not even two, but possibly three stars at the center of the nebula. Only one of these stars, the largest of the three, will have reached the end of its life; But the trio of stars, if all three actually exist, will likely be either too close together or too faint to be resolved separately. by JWST.
There is growing evidence that some planetary nebulae, at least those with complex structures, are formed by the intervention of a companion star into the dying star at the centre. For the South Rim, Kastner’s team suggests a triple system of nearby points. dual Orbits a third, more distant star within an orbital radius of 60 astronomical units binary (one astronomical unit, AU, is the distance between) Soil and the sun and our solar system 60 AU would be at the farthest edge of the world. Kuiper Belt).
The two lobes of the Southern Rim have a narrow or “tucked” waistline, like an hourglass; This is a common feature of planetary nebulae emanating from binary star systems where one of the stars has reached the end of its life. The binary companion may surround the material shed by the dying star, escaping poleward rather than equatorward, forming two lobes. JWST’s mid-infrared observations support this hypothesis by detecting an excess of infrared light from the central star system, a classic signature of a dusty disk formed by interactions between a red giant and a close binary companion.
This explains the initial ringtone. The origin of the second ring is less certain, the team says.
Although the Southern Rim appears bilobed, some material must have been ejected by the red giant in the form of a roughly spherical or ellipsoidal envelope of material; This is a rapid mass loss event that likely represents the last gasp of material the white will leave behind. dwarf. A binary star system produces a series of fast, narrow jets, but if a third star is present, the extra star gravity It acts on the inner binary, causing the direction of the jets to “wobble” like a top. These precessing jets may have created a circular cavity in the ellipsoidal component of the nebula, thus forming the second ring.
Kastner emphasizes that this explanation is still speculative, but the ionized void at the center of the nebula carries evidence of such jets in its structure.
Other ring-shaped planetary nebulae such as the Helix Nebula (NGC 7293) Aquarius), has also been shown to have bilobed structures in which we look “down” at the end of one lobe. Discovery of the second ring in the Southern Ring Nebula – or should that be the Southern Rings, now plural? – encourages astronomers to revisit some of the other well-known ring nebulae and see if they, too, are missing secondary rings.
Planetary nebulae don’t just signify stellar death. They also, in a sense, literally carry the promise of a new life.
“Where are the carbon, oxygen and nitrogen? Universe Kastner wonders: “We see this occurring in dying sun-like stars, like the star that just died and created the Southern Rim.”
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As an expanding planetary nebula disintegrates interstellar spaceIt disperses these molecules into the cosmos, where they form giant molecular clouds that form new generations of stars and planets.
“A lot of this molecular gas can get into the atmospheres of planets, and the atmospheres can make life possible,” says Kastner. As a matter of fact, all elements heavier than hydrogen and helium on Earth originated within stars and were ejected into space when the stars died.
As many experts say, we are literally made up of stars.
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 stellar birth and death anew. To quote Battlestar Galactica, it’s all happened before and it’ll all happen again.
The findings were published on April 2. Astrophysical Journal.