The new image of the famous Ring Nebula from Webb’s Near-InfraRed Camera (NIRCam) shows the intricate details of the filament structure of the nebula’s inner ring, while the new image from Webb’s Mid-InfraRed Instrument (MIRI) reveals particular details in the concentric features in the outer regions of the nebula’s ring.
This image from Webb’s NIRCam instrument shows the Ring Nebula. The nebula’s inner cavity hosts shades of blue and green, while the detailed ring transitions through shades of orange in the inner regions and pink in the outer region. The ring’s inner region has distinct filament elements. Image credit: NASA / ESA / CSA / Webb / M. Barlow / N. Cox / R. Wesson.
The Ring Nebula is an archetypal planetary nebula about 2,500 light-years away in the constellation of Lyra.
Also known as Messier 57, M57 or NGC 6720, the nebula was discovered in 1779 by French astronomers Antoine Darquier de Pellepoix and Charles Messier.
Both astronomers stumbled upon the nebula when trying to follow the path of Comet Bode through the constellation of Lyra, passing very close to the Ring Nebula.
“Planetary nebulae were once thought to be simple, round objects with a single dying star at the center,” said Cardiff University astronomer Roger Wesson.
“They were named for their fuzzy, planet-like appearance through small telescopes.”
“Only a few thousand years ago, that star was still a red giant that was shedding most of its mass. As a last farewell, the hot core now ionizes, or heats up, this expelled gas, and the nebula responds with colorful emission of light.”
“Modern observations, though, show that most planetary nebulae display breathtaking complexity. It begs the question: how does a spherical star create such intricate and delicate non-spherical structures?”
“The Ring Nebula is an ideal target to unravel some of the mysteries of planetary nebulae,” he said.
“It is nearby and bright — visible with binoculars on a clear summer evening from the northern hemisphere and much of the southern.”
“Our team, named the ESSENcE (Evolved StarS and their Nebulae in the JWST Era) team, is an international group of experts on planetary nebulae and related objects.”
“We realized that Webb observations would provide us with invaluable insights, since the Ring Nebula fits nicely in the field of view of Webb’s NIRCam and MIRI instruments, allowing us to study it in unprecedented spatial detail.”
This image from Webb’s MIRI instrument shows the Ring Nebula. The nebula’s inner cavity hosts shades of red and orange, while the detailed ring transitions through shades of yellow in the inner regions and blue/purple in the outer region. Image credit: NASA / ESA / CSA / Webb / M. Barlow / N. Cox / R. Wesson.
According to the team, there are some 20,000 dense globules in the nebula, which are rich in molecular hydrogen.
In contrast, the inner region shows very hot gas. The main shell contains a thin ring of enhanced emission from carbon-based molecules known as polycyclic aromatic hydrocarbons (PAHs).
Roughly ten concentric arcs are located just beyond the outer edge of the main ring.
The arcs are thought to originate from the interaction of the central star with a low-mass companion orbiting at a distance comparable to that between the Earth and the dwarf planet Pluto.
In this way, nebulae like the Ring Nebula reveal a kind of astronomical archaeology, as astronomers study the nebula to learn about the star that created it.
The Ring Nebula is shaped like a distorted doughnut. We are gazing almost directly down one of the poles of this structure, with a brightly colored barrel of material stretching away from us.
Although the center of this doughnut may look empty, it is actually full of lower density material that stretches both towards and away from us, creating a shape similar to a rugby ball slotted into the doughnut’s central gap.
The brightest part of the nebula is what we see as the colorful main ring. This is composed of gas thrown off by a dying star at the centre of the nebula.
This star is on its way to becoming a white dwarf — a very small, dense, and hot body that is the final evolutionary stage for a star like the Sun.
“When we first saw the images, we were stunned by the amount of detail in them,” Dr. Wesson said.
“The bright ring that gives the nebula its name is composed of about 20,000 individual clumps of dense molecular hydrogen gas, each of them about as massive as the Earth.”
“Within the ring, there is a narrow band of emission from PAHs — complex carbon-bearing molecules that we would not expect to form in the Ring Nebula.”
“Outside the bright ring, we see curious ‘spikes’ pointing directly away from the central star, which are prominent in the infrared but were only very faintly visible in Hubble images.”
“We think these could be due to molecules that can form in the shadows of the densest parts of the ring, where they are shielded from the direct, intense radiation from the hot central star.”
“Our MIRI images provided us with the sharpest and clearest view yet of the faint molecular halo outside the bright ring.”
“A surprising revelation was the presence of up to ten regularly-spaced, concentric features within this faint halo.”
“These arcs must have formed about every 280 years as the central star was shedding its outer layers.”
“When a single star evolves into a planetary nebula, there is no process that we know of that has that kind of time period.”
“Instead, these rings suggest that there must be a companion star in the system, orbiting about as far away from the central star as Pluto does from our Sun.”
“As the dying star was throwing off its atmosphere, the companion star shaped the outflow and sculpted it. No previous telescope had the sensitivity and the spatial resolution to uncover this subtle effect.”
“So how did a spherical star form such a structured and complicated nebulae as the Ring Nebula? A little help from a binary companion may well be part of the answer.”
