The James Webb Space Telescope captured detailed images of a massive protostar in Sharpless 2-284 about 15,000 light-years away, revealing twin plasma jets nearly 180 degrees apart. The jets’ symmetry and the protostar’s low-metallicity environment support the core accretion model of massive star formation and provide a rare laboratory for studying early-universe star formation. The results were published in The Astrophysical Journal.
James Webb Captures Massive Newborn Star Launching Twin Plasma Jets, Bolstering Core-Accretion Theory
NASA's James Webb Space Telescope recently imaged an extremely large and symmetric protostellar jet at the outskirts of our Milky Way galaxy in the forming cluster Sh2-284. From tip to tip, this protostellar jet is 8 light-years across, about double the distance from our Sun to its closest neighboring star system, Alpha Centauri.
A newborn, massive protostar roughly 15,000 light-years from Earth has been observed launching two powerful, oppositely directed streams of superheated plasma. Captured in striking detail by the James Webb Space Telescope (JWST), the twin jets emerge from a protostar inside the nebula Sharpless 2-284 (Sh2-284) and offer fresh evidence about how the most massive stars form.
The protostar in Sh2-284 already exceeds ten times the mass of the Sun. While many young stars produce jets, outflows on this scale are rare in the Milky Way, making this object a particularly valuable case study for early stellar evolution.
What JWST Revealed
JWST images show long, collimated jets of molecular hydrogen extending in nearly opposite directions. That geometry — with the two jet lobes aligned almost 180 degrees apart — indicates a stable, well-ordered accretion disk feeding the young star rather than a chaotic, rapidly changing feeding environment.
"We didn’t really know there was a massive star with this kind of super-jet out there before the observation," said Yu Cheng of Japan’s National Astronomical Observatory, a co-author of the study published in The Astrophysical Journal. "Such a spectacular outflow of molecular hydrogen from a massive star is rare in other regions of our galaxy."
Why This Matters
The observation helps distinguish between two long-standing models for massive star formation. The competitive accretion model predicts chaotic, multi-directional inflow that changes a protostar’s orientation over time, producing jets that can shift direction. The core accretion model predicts a stable central disk that maintains its orientation and drives symmetric, opposing jets. The nearly 180-degree alignment of the jets in Sh2-284 supports the core accretion scenario for this object.
Sh2-284 is also notable for its very low metallicity — it lacks significant amounts of elements heavier than hydrogen and helium. Low-metallicity environments resemble conditions in the early universe, so this protostar acts as a laboratory for studying how massive stars may have formed in earlier cosmic epochs.
"What we’ve seen here, because we’ve got the whole history — a tapestry of the story — is that the opposite sides of the jets are nearly 180 degrees apart from each other," said Jonathan Tan, an astronomer and co-author of the study. "That tells us that this central disk is held steady and validates a prediction of the core accretion theory."
Although this single object does not close the debate for all massive stars, the JWST observations provide powerful, high-resolution evidence that massive-star formation can proceed in remarkably ordered ways. The finding demonstrates the value of JWST’s sensitivity and resolution for resolving long-standing questions about star formation and galactic evolution.
Reference: Study published in The Astrophysical Journal; observations led in part by researchers at Japan’s National Astronomical Observatory.
