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March 14, 2023
The luminous, hot star called Wolf-Rayet 124 was imaged by NASA’s James Webb Space Telescope. Bright clumps of gas and dust appear like tadpoles swimming toward the star with tails streaming out behind them, blown back by the stellar wind. The surrounding nebula stretches about 10 light-years across. Credit: NASA, ESA, CSA, STScI, Webb ERO Production Team
A massive star on the cusp of death ejected huge volumes of hot gas into space. Webb’s Mid-Infrared Instrument revealed the structure of the material now surrounding the star.
The rare sight of a Wolf-Rayet star* – among the most luminous, most massive, and most briefly detectable stars known – was one of the first observations made by NASA’s James Webb Space Telescope in June 2022. Webb shows the star, WR 124, in unprecedented detail with its powerful infrared instruments. The star is 15,000 light-years away in the constellation Sagittarius.
Massive stars race through their lifecycles, and only some of them go through a brief Wolf-Rayet phase before going supernova, making Webb’s detailed observations of this rare phase valuable to astronomers. Wolf-Rayet stars are in the process of casting off their outer layers, resulting in their characteristic halos of gas and dust. The star WR 124 is 30 times the mass of the Sun and has shed 10 Suns’ worth of material – so far. As the ejected gas moves away from the star and cools, cosmic dust forms and glows in the infrared light detectable by Webb.
Cooler cosmic dust glows at longer mid-infrared wavelengths, displaying the structure of WR 124’s nebula in this image captured by Webb’s Mid-Infrared Instrument. The nebula is made of material cast off from the aging star in random ejections and from dust produced in the ensuing turbulence.
Credit: NASA, ESA, CSA, STScI, Webb ERO Production Team
The origin of cosmic dust that can survive a supernova blast and contribute to the universe’s overall “dust budget” is of great interest to astronomers for multiple reasons. Dust is integral to the workings of the universe: It shelters forming stars, gathers together to help form planets, and serves as a platform for molecules to form and clump together – including the building blocks of life on Earth. Despite the many essential roles that dust plays, there is still more dust in the universe than astronomers’ current dust-formation theories can explain. The universe is operating with a dust budget surplus.
Webb opens up new possibilities for studying details in cosmic dust, which is best observed in infrared wavelengths of light. Webb’s Near-Infrared Camera(NIRCam) balances the brightness of WR 124’s stellar core and the knotty details in the fainter surrounding gas. The telescope’s Mid-Infrared Instrument(MIRI) reveals the clumpy structure of the gas and dust nebula of the ejected material now surrounding the star. Before Webb, dust-loving astronomers simply did not have enough detailed information to explore questions of dust production in environments like WR 124 and whether the dust grains were large and bountiful enough to survive the supernova and become a significant contribution to the overall dust budget. Now those questions can be investigated with real data.
Stars like WR 124 also serve as an analog to help astronomers understand a crucial period in the early history of the universe. Similar dying stars first seeded the young universe with heavy elements forged in their cores – elements that are now common in the current era, including on Earth.
Webb’s detailed image of WR 124 preserves forever a brief, turbulent time of transformation, and promises future discoveries that will reveal the long-shrouded mysteries of cosmic dust.
The James Webb Space Telescope is the world’s premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency), and CSA (Canadian Space Agency).
MIRI was developed through a 50-50 partnership between NASA and ESA. NASA’s Jet Propulsion Laboratory led the U.S. efforts for MIRI, and a multinational consortium of European astronomical institutes contributes for ESA. George Rieke with the University of Arizona is the MIRI science team lead. Gillian Wright is the MIRI European principal investigator. Alistair Glasse with UK ATC is the MIRI instrument scientist, and Michael Ressler is the U.S. project scientist at JPL. Laszlo Tamas with UK ATC manages the European Consortium. The MIRI cryocooler development was led and managed by JPL, in collaboration with Northrop Grumman in Redondo Beach, California, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Caltech manages JPL for NASA.
For more information about the Webb mission, visit:
https://www.nasa.gov/webb
See: https://www.jpl.nasa.gov/news/nasas-webb-telescope-captures-rarely-seen-prelude-to-supernova?
utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20230314-1
* The Wolf-Rayet star:
M1-67 is the youngest wind-nebula around a Wolf-Rayet star, called WR124, in our Galaxy. Credit: ESO
Wolf-Rayet stars represent a final burst of activity before a huge star begins to die. These stars, which are at least 20 times more massive than the Sun, “live fast and die hard”, according to NASA.
Their endstate is more famous; it’s when they explode as supernova and seed the universe with cosmic elements that they get the most attention. But looking at how the star gets to that explosive stage is also important.
When you look at a star like the Sun, what you are seeing is a delicate equilibrium of the star’s gravity pulling stuff in, and nuclear fusion inside pushing pressure out. When the forces are about equal, you get a stable mass of fusing elements. For planets like ours lucky enough to live near a stable star, this period can go on for billions upon billions of years.
Being near a massive star is like playing with fire, however. They grow up quickly and thus die earlier in their lives than the Sun. And in the case of a Wolf-Rayet star, it’s run out of lighter elements to fuse inside its core. The Sun is happily churning hydrogen into helium, but Wolf-Rayets are ploughing through elements such as oxygen to try to keep equilibrium.
Because these elements have more atoms per unit, this creates more energy — specifically, heat and radiation, NASA says. The star begins to blow out winds reaching 2.2 million to 5.4 million miles per hour (3.6 million to 9 million kilometers per hour). Over time, the winds strip away the outer layers of the Wolf-Rayet. This eliminates much of its mass, while at the same time freeing its elements to be used elsewhere in the Universe.
Eventually, the star runs out of elements to fuse (the process can go no further than iron). When the fusion stops, the pressure inside the star ceases and there’s nothing to stop gravity from pushing in. Big stars explode as supernova. Bigger ones see their gravity warped so much that not even light can escape, creating a black hole.
We still have a lot to learn about stellar evolution, but a few studies over the years have provided insights. In 2004, for example, NASA issued reassuring news saying these stars don’t “die alone.” Most of them have a stellar companion, according to Hubble Space Telescope observations.
Because these elements have more atoms per unit, this creates more energy — specifically, heat and radiation, NASA says. The star begins to blow out winds reaching 2.2 million to 5.4 million miles per hour (3.6 million to 9 million kilometers per hour). Over time, the winds strip away the outer layers of the Wolf-Rayet. This eliminates much of its mass, while at the same time freeing its elements to be used elsewhere in the Universe.
Eventually, the star runs out of elements to fuse (the process can go no further than iron). When the fusion stops, the pressure inside the star ceases and there’s nothing to stop gravity from pushing in. Big stars explode as supernova. Bigger ones see their mass warping space time so much that not even light can escape, creating a black hole.
A composite image with Chandra data (purple) showing a “point-like source” beside the remains of a supernova, suggesting a companion star may have survived the explosion. Hydrogen is shown in optical light (yellow and cyan) from the Magellanic Cloud Emission Line Survey and there is also optical data available from the Digitized Sky Survey (white). Credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS
While at first glance this appears as just a simple observation, cosmologists said that it could help us figure out how these stars get so big and bright. For example: Maybe the bigger star (the one that turns into a Wolf-Rayet) feeds off its companion over time, gathering mass until it becomes stupendously big. With more fuel, the big stars burn out faster. Other things the smaller star could influence could be the bigger star’s rotation or orbit.
Here’s a few other facts about Wolf-Rayets, courtesy of astronomer David Darling:
Wolf-Rayets stars are divided into 3 classes based on their spectra, the WN stars (nitrogen dominant, some carbon), WC stars (carbon dominant, no nitrogen), and the rare WO stars with C/O < 1. The WN stars optical spectra show emission lines from H, NIII (4640Å), NIV, NV, HeI, HeII, and from CIV at 5808Å. In the UV, there are strong emission features from NII, NIII, NIV, NV, CIII, CIV, HeII, OIV, OV, and SiV.
The WC stars optical spectra show emission lines from H, CII, CIII (5696Å), CIV (5805Å), OV (5592Å), HeI, and HeII. No nitrogen lines are seen in the WC stars. In the UV, there are strong emission features from CII, CIII, CIV, OIV, OV, SiIV, HeII, FeIII, FeIV, and FeV.
Wolf-Rayet galaxies are galaxies that contain a large population of Wolf-Rayet stars. These emission-line galaxies show a broad 4686 He II emission feature due to the WR stars. About one-quarter of these galaxies also show broad N III 4640 A emission.
See: https://www.universetoday.com/24736/wolf-rayet-star/
See: https://lweb.cfa.harvard.edu/~pberlind/atlas/htmls/wrstars.html
Stars become a Wolf-Rayet stars when they've used up all or nearly all of their hydrogen. What happened to all the hydrogen? It became helium. The star's outward pressure will overrule the power of gravity and start ejecting out its energy in stellar winds. After converting helium, it starts to create Lithium, and so on up the Periodic Table until it reaches 26, Iron, when it can't process in its fusion furnace and explode. Becoming a Wolf-Rayet star is just one step up in the evolution of the star.
Hartmann352
The luminous, hot star called Wolf-Rayet 124 was imaged by NASA’s James Webb Space Telescope. Bright clumps of gas and dust appear like tadpoles swimming toward the star with tails streaming out behind them, blown back by the stellar wind. The surrounding nebula stretches about 10 light-years across. Credit: NASA, ESA, CSA, STScI, Webb ERO Production Team
A massive star on the cusp of death ejected huge volumes of hot gas into space. Webb’s Mid-Infrared Instrument revealed the structure of the material now surrounding the star.
The rare sight of a Wolf-Rayet star* – among the most luminous, most massive, and most briefly detectable stars known – was one of the first observations made by NASA’s James Webb Space Telescope in June 2022. Webb shows the star, WR 124, in unprecedented detail with its powerful infrared instruments. The star is 15,000 light-years away in the constellation Sagittarius.
Massive stars race through their lifecycles, and only some of them go through a brief Wolf-Rayet phase before going supernova, making Webb’s detailed observations of this rare phase valuable to astronomers. Wolf-Rayet stars are in the process of casting off their outer layers, resulting in their characteristic halos of gas and dust. The star WR 124 is 30 times the mass of the Sun and has shed 10 Suns’ worth of material – so far. As the ejected gas moves away from the star and cools, cosmic dust forms and glows in the infrared light detectable by Webb.
Cooler cosmic dust glows at longer mid-infrared wavelengths, displaying the structure of WR 124’s nebula in this image captured by Webb’s Mid-Infrared Instrument. The nebula is made of material cast off from the aging star in random ejections and from dust produced in the ensuing turbulence.
Credit: NASA, ESA, CSA, STScI, Webb ERO Production Team
The origin of cosmic dust that can survive a supernova blast and contribute to the universe’s overall “dust budget” is of great interest to astronomers for multiple reasons. Dust is integral to the workings of the universe: It shelters forming stars, gathers together to help form planets, and serves as a platform for molecules to form and clump together – including the building blocks of life on Earth. Despite the many essential roles that dust plays, there is still more dust in the universe than astronomers’ current dust-formation theories can explain. The universe is operating with a dust budget surplus.
Webb opens up new possibilities for studying details in cosmic dust, which is best observed in infrared wavelengths of light. Webb’s Near-Infrared Camera(NIRCam) balances the brightness of WR 124’s stellar core and the knotty details in the fainter surrounding gas. The telescope’s Mid-Infrared Instrument(MIRI) reveals the clumpy structure of the gas and dust nebula of the ejected material now surrounding the star. Before Webb, dust-loving astronomers simply did not have enough detailed information to explore questions of dust production in environments like WR 124 and whether the dust grains were large and bountiful enough to survive the supernova and become a significant contribution to the overall dust budget. Now those questions can be investigated with real data.
Stars like WR 124 also serve as an analog to help astronomers understand a crucial period in the early history of the universe. Similar dying stars first seeded the young universe with heavy elements forged in their cores – elements that are now common in the current era, including on Earth.
Webb’s detailed image of WR 124 preserves forever a brief, turbulent time of transformation, and promises future discoveries that will reveal the long-shrouded mysteries of cosmic dust.
The James Webb Space Telescope is the world’s premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency), and CSA (Canadian Space Agency).
MIRI was developed through a 50-50 partnership between NASA and ESA. NASA’s Jet Propulsion Laboratory led the U.S. efforts for MIRI, and a multinational consortium of European astronomical institutes contributes for ESA. George Rieke with the University of Arizona is the MIRI science team lead. Gillian Wright is the MIRI European principal investigator. Alistair Glasse with UK ATC is the MIRI instrument scientist, and Michael Ressler is the U.S. project scientist at JPL. Laszlo Tamas with UK ATC manages the European Consortium. The MIRI cryocooler development was led and managed by JPL, in collaboration with Northrop Grumman in Redondo Beach, California, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Caltech manages JPL for NASA.
For more information about the Webb mission, visit:
https://www.nasa.gov/webb
See: https://www.jpl.nasa.gov/news/nasas-webb-telescope-captures-rarely-seen-prelude-to-supernova?
utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20230314-1
* The Wolf-Rayet star:
M1-67 is the youngest wind-nebula around a Wolf-Rayet star, called WR124, in our Galaxy. Credit: ESO
Wolf-Rayet stars represent a final burst of activity before a huge star begins to die. These stars, which are at least 20 times more massive than the Sun, “live fast and die hard”, according to NASA.
Their endstate is more famous; it’s when they explode as supernova and seed the universe with cosmic elements that they get the most attention. But looking at how the star gets to that explosive stage is also important.
When you look at a star like the Sun, what you are seeing is a delicate equilibrium of the star’s gravity pulling stuff in, and nuclear fusion inside pushing pressure out. When the forces are about equal, you get a stable mass of fusing elements. For planets like ours lucky enough to live near a stable star, this period can go on for billions upon billions of years.
Being near a massive star is like playing with fire, however. They grow up quickly and thus die earlier in their lives than the Sun. And in the case of a Wolf-Rayet star, it’s run out of lighter elements to fuse inside its core. The Sun is happily churning hydrogen into helium, but Wolf-Rayets are ploughing through elements such as oxygen to try to keep equilibrium.
Because these elements have more atoms per unit, this creates more energy — specifically, heat and radiation, NASA says. The star begins to blow out winds reaching 2.2 million to 5.4 million miles per hour (3.6 million to 9 million kilometers per hour). Over time, the winds strip away the outer layers of the Wolf-Rayet. This eliminates much of its mass, while at the same time freeing its elements to be used elsewhere in the Universe.
Eventually, the star runs out of elements to fuse (the process can go no further than iron). When the fusion stops, the pressure inside the star ceases and there’s nothing to stop gravity from pushing in. Big stars explode as supernova. Bigger ones see their gravity warped so much that not even light can escape, creating a black hole.
We still have a lot to learn about stellar evolution, but a few studies over the years have provided insights. In 2004, for example, NASA issued reassuring news saying these stars don’t “die alone.” Most of them have a stellar companion, according to Hubble Space Telescope observations.
Because these elements have more atoms per unit, this creates more energy — specifically, heat and radiation, NASA says. The star begins to blow out winds reaching 2.2 million to 5.4 million miles per hour (3.6 million to 9 million kilometers per hour). Over time, the winds strip away the outer layers of the Wolf-Rayet. This eliminates much of its mass, while at the same time freeing its elements to be used elsewhere in the Universe.
Eventually, the star runs out of elements to fuse (the process can go no further than iron). When the fusion stops, the pressure inside the star ceases and there’s nothing to stop gravity from pushing in. Big stars explode as supernova. Bigger ones see their mass warping space time so much that not even light can escape, creating a black hole.
A composite image with Chandra data (purple) showing a “point-like source” beside the remains of a supernova, suggesting a companion star may have survived the explosion. Hydrogen is shown in optical light (yellow and cyan) from the Magellanic Cloud Emission Line Survey and there is also optical data available from the Digitized Sky Survey (white). Credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS
While at first glance this appears as just a simple observation, cosmologists said that it could help us figure out how these stars get so big and bright. For example: Maybe the bigger star (the one that turns into a Wolf-Rayet) feeds off its companion over time, gathering mass until it becomes stupendously big. With more fuel, the big stars burn out faster. Other things the smaller star could influence could be the bigger star’s rotation or orbit.
Here’s a few other facts about Wolf-Rayets, courtesy of astronomer David Darling:
- Their names come from two French astronomers, Charles Wolf and Georges Rayet, who discovered the first known star of this kind in 1867.
- Wolf-Rayets come in two flavours: WN (emission lines of helium and nitrogen) and WC (carbon, oxygen and hydrogen).
- Stars like our Sun evolve into more massive red giants as they run out of hydrogen to burn in the core. When these stars begin to shed their outer layers, they behave somewhat similarly to Wolf-Rayets. So they’re called “Wolf-Rayet type stars”, although they’re not exactly the same thing.
Wolf-Rayets stars are divided into 3 classes based on their spectra, the WN stars (nitrogen dominant, some carbon), WC stars (carbon dominant, no nitrogen), and the rare WO stars with C/O < 1. The WN stars optical spectra show emission lines from H, NIII (4640Å), NIV, NV, HeI, HeII, and from CIV at 5808Å. In the UV, there are strong emission features from NII, NIII, NIV, NV, CIII, CIV, HeII, OIV, OV, and SiV.
The WC stars optical spectra show emission lines from H, CII, CIII (5696Å), CIV (5805Å), OV (5592Å), HeI, and HeII. No nitrogen lines are seen in the WC stars. In the UV, there are strong emission features from CII, CIII, CIV, OIV, OV, SiIV, HeII, FeIII, FeIV, and FeV.
Wolf-Rayet galaxies are galaxies that contain a large population of Wolf-Rayet stars. These emission-line galaxies show a broad 4686 He II emission feature due to the WR stars. About one-quarter of these galaxies also show broad N III 4640 A emission.
See: https://www.universetoday.com/24736/wolf-rayet-star/
See: https://lweb.cfa.harvard.edu/~pberlind/atlas/htmls/wrstars.html
Stars become a Wolf-Rayet stars when they've used up all or nearly all of their hydrogen. What happened to all the hydrogen? It became helium. The star's outward pressure will overrule the power of gravity and start ejecting out its energy in stellar winds. After converting helium, it starts to create Lithium, and so on up the Periodic Table until it reaches 26, Iron, when it can't process in its fusion furnace and explode. Becoming a Wolf-Rayet star is just one step up in the evolution of the star.
Hartmann352
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