This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: When astronomers looked at photos of the early universe taken by the James Webb Space Telescope, they found something odd: an overabundance of bright galaxies. Based on what they knew about the early universe, such galaxies should have been far less common in the few hundred million years following the Big Bang.
Now, using cutting-edge simulations, researchers at the Simons Foundation's Flatiron Institute in New York City and the University of Texas at Dallas have an answer to this mystery: Powerful ultraviolet radiation produced by clusters of young stars acted like a leaf blower, flinging light-blocking gas and dust out of the galaxy and thereby making the galaxies appear brighter. The researchers report their findings on this ultraviolet light, called Lyman-alpha radiation, on Nov. 4 in The Astrophysical Journal. "Our results show Lyman-alpha radiation can push low-density gas and dust away really, really fast," says Shyam Menon, a research fellow at the Flatiron Institute's Center for Computational Astrophysics and the study's lead author.
"It can sort of clear the 'fog,' allowing us to see stars in the early universe much more clearly than we would otherwise." Lyman-alpha radiation is created when an electron and a hydrogen atom collide or when an electron joins up with a hydrogen ion. In powerful stellar environments where Lyman-alpha radiation is abundant, the pressure from the light is thought to play a role in sculpting stellar nurseries. When the Lyman-alpha radiation hits gas or dust, the material absorbs the energy and recoils from the impact like a baseball catcher's mitt catching a fastball.
This effect launches the material outward, leaving less material available to form a star. Some astronomers wondered whether, in extreme cases, the effect could be strong enough to halt star formation. "We've known for a very long time that Lyman-alpha radiation could be important because it carries a lot of force," Menon says.
"But we've never actually been able to estimate how important it is in a realistic environment because of how challenging it is to model." Lyman-alpha radiation differs from many other types of radiation in how it interacts with matter. When an atom or dust grain absorbs most kinds of light, it typically re-emits that energy at a different wavelength, making the light much less likely to be absorbed again. But when hydrogen atoms absorb Lyman-alpha radiation, they almost immediately re-emit it at the same wavelength.
This means nearby hydrogen atoms can absorb the light over and over before it finally escapes. While this repeated absorption and re-emission makes Lyman-alpha a particularly powerful source of radiation pressure, it also makes it computationally challenging to simulate because each interaction must be modeled. Instead of directly simulating this radiation recycling, Menon and his collaborator, Aaron Smith at the University of Texas at Dallas, developed a workaround.
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