Oversized Galaxies?

Credit: NASA/JPL-Caltech

When astronomers first glimpsed galaxies in the early universe with NASA’s James Webb Space Telescope, they got a big surprise: some galaxies appeared to have grown so massive, so quickly, that simulations could not account for them. Some researchers suggested that the standard model of cosmology, which explains what the universe is made of and how it has evolved since the big bang, may be flawed.

However, a study led by University of Texas at Austin graduate student Katherine Chworowsky found that black holes, which rapidly consume gas, make some of the galaxies appear brighter and bigger than they really are as friction in the fast-moving gas emits heat and light. This extra light makes it appear that the galaxies contain more stars and are more massive than astronomers would otherwise estimate.

The evidence for the study was provided by Webb’s Cosmic Evolution Early Release Science Survey, led by Steven Finkelstein, a professor of astronomy at UT and study co-author.

While researchers now understand that the standard model’s predictions on the size of early galaxies fit the observations, there are still about twice as many massive galaxies in Webb’s data of the early universe as expected. One reason might be that stars formed more quickly in the early universe than they do today. Their work points to the need for new ideas in star formation.

“And so, there is still that sense of intrigue,” Chworowsky said. “That’s what makes doing this kind of science fun, because it’d be a terribly boring field if one paper figured everything out, or there were no more questions to answer.”

“It’d be a terribly boring field if one paper figured everything out”