Watch as EarthSky’s Will Triggs talks about red monsters, massive galaxies in the early universe.
The 2025 EarthSky Lunar Calendar is now available! A unique and beautiful poster-sized calendar. Makes a great gift. Get yours today!
Red monsters were giant early galaxies
Astronomers thought galaxies in the early universe wouldn’t be too massive, because star production was just getting started. But the Webb Space Telescope recently discovered three “red monsters,” or massive, dusty galaxies that existed within the first billion years after the Big Bang. An international team of scientists said on November 13, 2024, that these galaxies were nearly as large as our own Milky Way galaxy. Therefore, our current models of galaxy formation will need some rethinking.
Presently, the leading theory of galaxy formation states that they form slowly, within halos of dark matter. Scientists thought that the gas trapped by these halos wasn’t particularly efficient at forming stars and, eventually, galaxies. But based on how early these massive galaxies appeared, the process must be more efficient than suspected.
Co-author Stijn Wuyts of Bath University said:
Finding three such massive beasts among the sample poses a tantalizing puzzle. Many processes in galaxy evolution have a tendency to introduce a rate-limiting step in how efficiently gas can convert into stars, yet somehow these red monsters appear to have swiftly evaded most of these hurdles.
The team published their results in the peer-reviewed journal Nature on November 13, 2024.
How did they find the red monsters?
The Webb Space Telescope has powerful infrared vision that lets astronomers peer through dusty environments and get a peek at the early universe. In November 2022 and February 2023, Webb took long looks deep into space during the First Reionization Epoch Spectroscopically Complete Observations (FRESCO) survey.
While most of the galaxies in the survey fit the current model for galaxy formation, there were three surprises: the red monsters. These galaxies form stars twice as efficiently as the others. And because they have a high dust content, they appear redder, which earned them their name. Co-author David Elbaz of CEA Paris-Saclay said:
The massive properties of these ‘red monsters’ were hardly determined before JWST [James Webb Space Telescope], as they are optically invisible due to dust attenuation.
FRESCO’s goal was to:
… systematically analyze a complete sample of emission-line galaxies within the first billion years of cosmic history.
Emission-line galaxies are those that have strong emission lines in their spectra. So certain wavelengths appear brighter in these galaxies. These bright emission lines helped the astronomers pinpoint their distance from us. Then, knowing their spectra and distances led to a measurement of how many stars were within the galaxies.
Co-author Pascal Oesch of the University of Geneva said spectroscopy with Webb enabled them to:
identify and study the growth of galaxies over time, and to obtain a clearer picture of how stellar mass accumulates over the course of cosmic history.
More research ahead
The discovery of the red monsters isn’t a complete upheaval of what we understand about the formation of stars and galaxies in the early universe. But it does contribute to the existing question of how there can be so many massive galaxies so close to the Big Bang.
Lead author Mengyuan Xiao of the University of Geneva said:
Our findings are reshaping our understanding of galaxy formation in the early universe. These results indicate that galaxies in the early universe could form stars with unexpected efficiency. As we study these galaxies in more depth, they will offer new insights into the conditions that shaped the universe’s earliest epochs. The ‘red monsters’ are just the beginning of a new era in our exploration of the early universe.
Bottom line: Red monsters were massive galaxies in the early universe. Astronomers aren’t yet sure how these galaxies became so massive so soon after the Big Bang.
Source: Accelerated formation of ultra-massive galaxies in the first billion years
Via University of Geneva
Via Bath University