- 3779 - RING NEBULA - new pictures from Webb? The Ring Nebula is located 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.
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--------------------- 3779 - RING NEBULA - new pictures from Webb?
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-------------------- An image of the Southern Ring Nebula
- The nebula, “NGC 3132“, had been previously imaged by Webb's predecessor, the Hubble Space Telescope. But Hubble's photographs, while stunning, failed to convey the whole truth about this dust cloud, which sprang up from an implosion of a dying star about the size of the sun merely 2,500 years ago.
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- The Southern Ring Nebula is a “planetary nebula“, It is the product of the implosion of a red giant star. When a star somewhat bigger than the sun runs out of hydrogen fuel in its core, it swells into a red giant, which can be hundreds of times wider than the original star. Eventually the red giant sheds its outer layers, which then form the nebula, and contracts into cooling remnants called a “white dwarf“.
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- In the images from Hubble, the shed layers form a rather smooth ring-shaped cloud, while the white dwarf can be seen as a small speck of light at the center of the ring, outshone by a much brighter, still fully alive, companion star some 1,300 sun-Earth distances away.
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- Webb provided a more complex view of the nebula. The telescope imaged the cloud with two of its instruments, the Near Infrared Camera (NIRCam), which sees warmer objects such as stars, and the Mid-Infrared Instrument (MIRI), which is a champion at spotting dust.
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- It was MIRI's view that immediately sparked the astronomers' interest. Instead of the one large and one tiny star known from Hubble's view, two stars of equal sizes emerged. And strangely, the star that the astronomers knew as the white dwarf was unexpectedly red.
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- White dwarfs are hot, they don't shine in this wavelength. So astronomers knew that there must be a lot of cool dust enshrouding the white dwarf, there is a cool disk of dust.
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- Astronomers wondered how the dust disk came into being. Such disks are usually made of material from a smaller star orbiting a more massive star, whose gravity disturbs the companion. But the known bright companion of the white dwarf at the center of the Southern Ring Nebula was too far away to be affected by the white dwarf. The only plausible conclusion was that another, invisible small star was orbiting the white dwarf much closer in, releasing the dust. The system of two stars suddenly became a system of three.
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- The relatively smooth surface of the ring-shaped cloud seen by Hubble, turned into a mass of swirling streams and dust filaments. One feature especially caught the astronomers' eyes: concentric layers spreading outward toward the ring's edges like ripples in a pond. Astronomers have seen such concentric shells before, including in Webb's images of the nebula surrounding a giant star known as WR140.
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- The NIRCam image of the Southern Ring Nebula revealed concentric ripples in the ring-shaped cloud
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- There are many nebulas with arches like that. Modeling where the arches come from, requires that you have an orbiting companion, and when the star ejects the nebula, the nebula streams past the orbiting companion that acts like a sprinkler and creates a spiral that is ingrained into the expanding nebula.
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- By measuring the distance between the concentric rings, astronomers can learn a lot about the companion star that created the structures including its distance from the white dwarf whose ejected envelope created the nebula. The distance calculation suggested that neither of the two companions, the visible one and the one responsible for the dusty disk, could have caused the ripples. A third star, somewhere in between the two, was added into the system.
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- Further investigations of the nebula's shape revealed even that a fifth star may be hiding within the dusty disk close to the white dwarf. Astronomers think that all the gas and dust was thrown all over the place in the Southern Ring Nebula must have come from that one star.
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December 10, 2022 RING NEBULA - new pictures from Webb? 3779
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