There are a lot of major research questions that researchers initially figured that JWST would answer after it launched in the early twenty-teens, but when that massive space telescope got delayed and delayed, researchers creatively came up with other ways to get the data they needed. Through a combination of computer models and creative telescope use, the astronomy community built up a picture of mass coming together, galaxies building up, and stars forming throughout the mix.

And that star-forming was just a healthy, run-of-the-mill, slow and steady, regular rate.

But that understanding came from more computer models than observatory data.

Using new data coming to us through the combined efforts of the Hubble Space Telescope (HST) and the utilization of galaxy clusters as gravitational lenses, researchers have found ways to start to image distant galaxies. And thanks to the time it takes light to reach us, we’re seeing galaxies as they appeared early in the universe.

Sixty to ninety percent of those galaxies, a new paper in The Astrophysical Journal points out, were experiencing extremely high levels of star formation, consistent with them being star-bursting galaxies. This work is led by Pierluigi Rinaldi.

In a not-starbursting galaxy, like our own Milky Way, we see pockets of star formation associated with giant molecular clouds collapsing into stars and forming star clusters. These galaxies may form one to a few stars a year, and these pockets of star formation are generally triggered by regular events like supernovae, collisions between clouds, and other minor shocks.

In starbursting systems, massive events, such as the collision between two systems, can cause the bulk of the gas and dust in a system to engage in star formation. These kinds of galaxy-wide events generally last 10-100 million years, and galaxies can undergo multiple bursts of star formation over time.

Current models of the evolution of the early universe don’t predict a lot of starburst behavior.

But the epic combination of Hubble, the Spitzer Space Telescope, and the ground-based Very Large Telescope was able to observe 20,000 distant galaxies. This group found that 20-40% of star-forming galaxies are undergoing starbursts and were forming 60-90% of new stars. This is compared to today’s rate of about 10% of stars coming from starburst galaxies. According to Rinaldi: Even the latest and most sophisticated models of galaxy formation had not predicted this. It seems likely that the physical processes occur at too small a scale for the models to account for them.

Future research that will continue exploring what our computer models must be missing is already funded through an NWO Vici grant, and when we find out how 20-40% of early galaxies got shocked into forming stars, we’ll let you know, right here, at the Daily Space.

More Information

NOVA press release

“The galaxy starburst/main-sequence bimodality over five decades in stellar mass at z ~ 3-6.5,” Pierluigi Rinaldi et al., to be published in The Astrophysical Journal (preprint on arxiv.org)