Webb telescope reveals glowing star crime scene
2,500 years ago, one of the most beautiful features of the cosmos was born: the Southern Ring Nebula. The nebula was vividly imaged by the Webb Space Telescope earlier this year, and now astronomers think they know exactly how the powerful starburst happened, leaving the elegant nebula in its wake.
The star that carried the nebula was about three times the size of the Sun and 500 million years old. That’s pretty young, in stellar terms; our Sun is about 4.6 billion years old and 5 billion more must live.
About 2,500 years ago, Confucius and Buddha were still alive. The Peloponnesian Wars were about to begin. And sometime during those years, a star 2,000 light-years away disappeared, shooting gas outward from a newly formed white dwarf.
The Southern Ring Nebula’s star isn’t dead — not yet — but the outgassing is an important turning point in the star’s life. White dwarfs are the stellar endgame; they form when stars have exhausted their nuclear energy and begin their slow cooling.
Thanks to images from the Webb Space Telescope and smart computing and mathematical modeling by the research teamthe moments leading up to the Southern Ring Nebula’s stellar light show can now to be considered in detail.
Different Webb filters highlight different aspects of a light source therefore some parts of the nebula may appear pearly or translucent red, while others appear blue or orange, depending on the image. Web image processors choose highlight different aspects of the objects in order to display different elements – hot gas, for exampleor star factories within larger systems.
A team of 70 astronomers worked together to determine that up to five stars (only two of which are now visible) may have been involved in the stellar demise. Their investigation into the star’s death is published today in Nature Astronomy.
“We were surprised to find evidence of two or three companion stars that probably precipitated its demise, as well as another ‘innocent bystander’ star that was caught up in the interaction,” said Orsola De Marco, an astronomer at Macquarie University and the researcher lead author, at Univ exemption.
The team’s play-by-play of the nebula’s origins was made possible by very precise measurements of the brightest star (the star among stars, if you will) in Webb imagician. Data from Webb allowed researchers to accurately measure its mass and how far along it is in its lifewhich in turn allowed them to extract the mass of the central faint star before it ejects its material and creates the color nebula.
Webb imaged the Southern Ring with two instruments, NIRcam and MIRI. Webb’s images were complemented by data from the European Southern Observatory’s Very Large Telescope, the San Pedro de Mártir telescope, and NASA’s Gaia and Hubble space telescopes.
Only two of stars believed to be involved in this cosmic fury are seen in Web‘c representative color photograph of the nebula, taken with NIRcam. The bright star at the center of the nebula is a partner to the one that ejected so much material that it became a white dwarf. This desiccated (and exhausted) star sits faintly along the 8 o’clock diffraction peak of the bright central star in the image above.
Astronomers believe that at least one star interacted with the fainter star (star 1 in the timeline illustrated below), as the latter swells, preparing to expel its gas and become a white dwarf.
According to the team, this mysterious star (Star 3) ejected jets of material as it interacted with the dying star and covered the faint star in dust before merging with the dwarf. Star 2 in the illustration is now the bright spot in the center of the nebula—a relatively strong character, given the lack of explosive activity or outgassing.
Another star (or “party guy” in Space Telescope Science Institute analogy of an astrophysics fest gone awry) picked up gas and dust dropped by its progenitor, causing ripples in the material. Another star (star 5 in the panels above) then orbited the light show and created the ring system surrounding the nebula.
According to the researchers’ calculations, you can consider the white dwarf near the nebula’s core to be the host of the party, which raves too loudly and passes out well before the party is over. But the star gave everyone a great time while it was up, and thanks to him, the party continued.
“We think that all this gas and dust that we see scattered everywhere must come from this one star, but it’s been thrown in very specific directions by its companion stars,” Joel Kastner, an astrophysicist at the Rochester Institute of Technology, told StScI exemption.
The researchers believe that the same methods that revealed the specifics of the birth of the Southern Ring Nebula could help to unpack the births of other nebulae, as well as the astrophysical forces at work in the interactions of stars.
The images that revealed this interstellar scene were released in June; only now have researchers had time to sift through the data and present their interpretation.