A newborn star 15,000 light-years from Earth is fascinating astronomers with its dual blasts of superheated plasma jets. The rare sight captured in stunning detail by the James Webb Space Telescope (JWST) isnât only a display of cosmic forces. Itâs helping solve a decadesâ long debate about the origins of massive stellar objects.
Located at the edge of the Milky Way galaxy inside a nebula known as Sharpless 2-284 (Sh2-284), the young protostar is already upwards of 10 times the mass of our sun. But while researchers have observed hundreds of stellar jets from other young stars, few occur in such a gargantuan example as Sh2-284.
âWe didnât really know there was a massive star with this kind of super-jet out there before the observation. Such a spectacular outflow of molecular hydrogen from a massive star is rare in other regions of our galaxy,â explained Yu Cheng, an astronomer at Japanâs National Astronomical Observatory and co-author of a study on Sh2-284 published in The Astrophysical Journal.
By studying the protostar and its jets, researchers can refine their models for early stellar activity. Sh2-284âs location also offers an approximation of a much younger universe. The protostar lives at the edge of our galaxy, and lacks elements heavier than hydrogen and helium. The measurement of these elemental proportions in a protostar is known as metallicity. Stars with low metallicity mirror the cosmic bodies that existed during a much earlier era of the universe, including soon after the Big Bang.
âMassive stars, like the one found inside this cluster, have very important influences on the evolution of galaxies,â said Cheng. âOur discovery is shedding light on the formation mechanism of massive stars in low metallicity environments, so we can use this massive star as a laboratory to study what was going on in earlier cosmic history.â
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For over 30 years, experts have been debating the evolution of massive stars and often support one of two theories. The competitive accretion theory posits that an incredibly chaotic amassing of materials coming in from different directions creates the protostar. These influences shift a protostarâs orientation over time, with jet excretions flowing out perpendicularly above and below the swirling disk. On the other hand, the core accretion theory features a much more stable stellar evolution process.
âWhat weâve seen here, because weâve got the whole historyâa tapestry of the storyâis that the opposite sides of the jets are nearly 180 degrees apart from each other,â added Jonathan Tan, an astronomer and study co-author. âThat tells us that this central disk is held steady and validates a prediction of the core accretion theory.â
Despite its measurements and powerful plasma jets, Sh2-284 is showing researchers that massive stars can be born through remarkably stable conditions. Without the JWST, the accretion debate could have easily continued for another three decades. But while the argument may be nearly settled, it still amazes its observers.
âI was really surprised at the order, symmetry, and size of the jet when we first looked at it,â said Tan.
