GIANT GALAXIES EMERGED EARLY IN THE DAWN OF THE UNIVERSE
These objects challenge cosmological models of how the universe evolved.
Astronomers using the James Webb Space Telescope (JWST) have found six massive galaxies with roughly as many stars as our own Milky Way, but in the cosmic dawn less than a billion years after the Big Bang.
These galaxies are not supposed to exist at such early times. Galaxies like our own take billions of years to amass their hundreds of billions of stars. To put it in perspective, a galaxy that is madly churning out stars produces only 100 Suns’ worth of stars per year. And our own staid Milky Way makes only a handful of stars per year that together weigh about as much as our Sun. So, the galaxies spotted by JWST would have had to be massively productive since the dawn of the universe — and the first stars didn’t even turn on until 100 million years after the Big Bang, shrinking the timeline even further.
What’s more, standard cosmology states that at such early times, there simply wasn’t enough baryonic matter — the normal stuff stars (and people and rocks) are made of — in a small enough area to make so many stars.
Each of the galaxies discovered has tens of billions of stars, with some sporting perhaps as many as 100 billion stars. Most astronomers think it took the universe a few billion years to clump up enough to allow for massive galaxies.
Until now, that’s what observations have shown too: small galaxies with fewer stars in the early universe.
In other words, these newfound galaxies imply either that scientists are wrong about standard cosmology — always an exciting idea — or wrong about how galaxies form and evolve, which is equally intriguing.
Shared online as a preprint last
July, the work was peer-reviewed and published by the journal Nature Feb. 22.
LOOKING FAR AFIELD
The data come from one of JWST’s first projects — to observe a seemingly empty chunk of space near the Big
Dipper. By looking into the darkness, away from more obvious targets, telescopes can peer into the distant universe, revealing galaxies, quasars, and more from the first billion years of the universe. Dubbed the Cosmic Evolution Early Release Science (CEERS) Survey, the project was meant to gather a large batch of galaxy data from the distant universe. The Hubble Space Telescope looked at this same patch of sky in the 1990s and found plenty of small, early galaxies with few stars, as expected.
The light from these distant objects is not only faint, but it has been shifted to longer, redder wavelengths over the course of its awesome journey. Light from young stars is emitted at ultraviolet wavelengths; by the time it gets to the present-day universe, it is infrared light — JWST’s specialty. Astronomers expected JWST to find more baby galaxies, adding to Hubble’s haul. But it also found those six massive galaxies already formed some 500 million to 700 million years after the Big Bang.
EXAMINING ALL AVENUES
It is possible that astronomers have mischaracterized these galaxies. Obtaining spectra will give more detail about the galaxies’ distance and makeup. The galaxies could be closer than they appear or smaller than calculated. They may not even be galaxies at all, but instead be supermassive black holes shrouded in dust and surrounded by glowing accretion disks.
However, there are currently six of these potential galaxy hulks where there should be none. “If even one of these galaxies is real, it will push against the limits of our understanding of cosmology,” said study co-author Erica Nelson of the University of Colorado at Boulder in a statement.