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A team of scientists, including Guðmundur Stefánsson of Princeton, have investigated the mysterious Blue Ring Nebula, made up of expanding (blue) hydrogen gas developing from a central star, which is the residual nucleus of a stellar fusion. Red filaments are shock wave filaments from the fusion event. Credit: NASA / JPL-Caltech / M. Seibert (Carnegie Institution for Science) / K. Team Hoadley (Caltech) / GALEX
Scientists have discovered a rare object called the Blue Ring Nebula, a ring of hydrogen gas with a star at its center. The properties of this system suggest that this is the remnant of two stars meeting their ultimate demise: an inner orbital dance that resulted in the two stars merging. The result offers a new window into the fate of many narrow orbiting binary star systems.
In 2004, scientists with NASA‘s Galaxy Evolution Explorer spotted an object unlike anything they had seen in our Milky Way Galaxy: a large, faint drop of gas that appeared to have a star in its center. In the ultraviolet wavelengths used by the satellite, the spot appeared blue – although it did not emit light visible to the human eye – and careful observations identified two thick rings inside, of so the team nicknamed it the Blue Ring Nebula. Over the next 16 years, they studied it with several terrestrial and space telescopes, but the more they learned, the more mysterious it seemed.
A team of scientists including Princeton UniversityGuðmundur Stefánsson, Henry Norris Russell Postdoctoral Fellow in Astrophysical Sciences, combined ground observations with detailed theoretical modeling to study the properties of the object. The article outlining their findings will appear in the November 19, 2020 issue of Nature.
“We were observing one night, with a new spectrograph that we had recently built, when we received a message from our colleagues about a particular object composed of a nebulous gas growing rapidly away from a central star, ”Stefánsson said. “How did he form? What are the properties of the central star? We were immediately thrilled to help solve the mystery! “
Most stars in the Milky Way are in binary systems – pairs of stars orbiting each other. If they are close enough to each other, these systems can meet their disappearance during a stellar fusion event: as the stars evolve, they expand, and if they are sufficiently close to one of them. the other, one of the stars can engulf its orbiting mate, causing the mate to spiral until the two stars collide. When the companion loses its orbital energy, it can eject matter at high speed.
Could this explain the mysterious Blue Ring Nebula?
Further evidence to support this hypothesis came from observations with two different spectrographs on large ground telescopes: the HIRES optical spectrograph on the 10-meter Keck telescope at the top of Maunakea in Hawaii, and the planet detector in the near-infrared habitable zone on the 10-meter Hobby-Eberly Telescope at McDonald Observatory in Texas, a new near-infrared spectrograph that Stefánsson helped design, build and commission to detect planets around nearby stars.
The Blue Ring Nebula consists of two expanding cones of debris. The base of a cone moves towards the Earth. Both bases are circled in magenta, revealing shock waves created as debris travels through space. Blue represents the material behind the shock wave and is only visible where the cones overlap. Credit: NASA /JPL-Caltech / R. Hurt
“The spectroscopic observations were essential in allowing us to better understand the object, from which we see that the central star is inflated, and we see accretion signatures probably from a surrounding debris disc,” Stefánsson said.
“Indeed, spectroscopic data coupled with theoretical modeling shows that the Blue Ring Nebula is consistent with the image of a merging binary star system, suggesting that the inward spiral companion was probably a low mass star, ”said Keri Hoadley, postdoctoral fellow. at Caltech and lead author of the article.
Although the relics of a few of these binary fusion events have already been observed, all of these objects have been enveloped in dust and opaque clouds, obstructing the view of the properties of the central stellar remnant. The Blue Ring Nebula is the only object allowing a clear view of the central stellar remnant, providing a clear window into its properties and giving clues to the fusion process.
“The Blue Ring Nebula is rare,” Hoadley said. “As such, it’s really exciting that we were able to find it, and we’re excited about the possibility of finding more of this type in the future. If so, it would give us a better understanding of the remnants of stellar fusion and the processes that govern them.
Read the troubling 16-year-old cosmic mystery solved, revealing the missing stellar link to learn more about this study.
Reference: “A blue ring nebula from a stellar fusion several thousand years ago” by Keri Hoadley, D. Christopher Martin, Brian D. Metzger, Mark Seibert, Andrew McWilliam, Ken J. Shen, James D . Neill, Gudmundur Stefansson, Andrew Monson and Bradley E. Schaefer, November 18, 2020, Nature.
DOI: 10.1038 / s41586-020-2893-5
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