Webb and Hubble Reveal 9,000 Star Clusters, Linking 5-Million-Year Clearout to Cosmic Reionization
Updated
Updated · UMass News and Media Relations · May 20
Webb and Hubble Reveal 9,000 Star Clusters, Linking 5-Million-Year Clearout to Cosmic Reionization
1 articles · Updated · UMass News and Media Relations · May 20
Nearly 9,000 young star clusters in four nearby galaxies were mapped with Webb and Hubble, giving astronomers their first broad view of stars just after birth inside gas-rich natal clouds.
The Nature Astronomy study found the most massive clusters blow away those clouds in about 5 million years, while less massive clusters emerge only after roughly 7 to 8 million years.
Webb’s infrared data pierced the gas and Hubble’s ultraviolet-optical images captured unobscured clusters, letting the team sort embedded, partially cleared and fully exposed clusters across Messier 51, Messier 83, NGC 628 and NGC 4449.
That faster escape by massive clusters strengthens the case that star formation—not just quasars—supplied enough ultraviolet photons to drive the universe’s reionization after the Big Bang.
The result also gives new constraints for galaxy and planet-formation models, because earlier gas clearing changes stellar feedback and exposes protoplanetary disks sooner to harsh radiation.
Do the universe's most massive star nurseries destroy the potential for planets to form around them?
Massive clusters or tiny galaxies: which cosmic force truly re-lit our universe after its dark ages?
Rapid Emergence of Star Clusters in 5 Million Years: New Insights from JWST and Hubble Observations
Overview
A groundbreaking study published in May 2026 combined the power of the James Webb and Hubble Space Telescopes to reveal how star clusters form and evolve much faster than previously thought. By observing nearly 9,000 star clusters in four nearby galaxies, researchers found that massive clusters can clear away their birth clouds and become visible in just five million years, while less massive clusters take up to eight million years. This discovery challenges earlier ideas about star cluster development and provides a clearer picture of how these stellar nurseries emerge from dense clouds of gas and dust.