This week, astronomers announced perhaps the most exciting such discovery yet. Among other discoveries, they found RUBIES-UDS-QG-z7, the farthest, most distant and earliest massive quiescent galaxy ever observed. The monumental discovery stems from data gathered by the incredible James Webb Space Telescope (JWST). It gives astronomers an unprecedented opportunity to peer back in time to the early days of the universe, about 700 million years after the Big Bang, when the universe was only about 5 percent of its current age.
Apart from its remarkable mass, RUBIES-UDS-QG-z7 is notable for its surprising quiescence. Researchers found that the galaxy had already ceased star formation between 50 to 100 million years before its light reached Earth. This conclusion is especially surprising in light of the fact that other galaxies from this era were still vigorously forming stars. The consequences of this stunning discovery really puts current models and theories towards the process of star formation in the early universe to the test.
The light we see from RUBIES-UDS-QG-z7 has traveled for nearly 13 billion years. This amazing distance ensures that it is one of the rarest of the rare in our vast Universe.
A Surprising Formation History
Together, the mass and the reconstructed formation history of RUBIES-UDS-QG-z7 tell a surprising story. This galaxy must have had very efficient star formation at an early stage of its life. Andrea Weibel, a member of the research team, emphasized the importance of this efficiency.
“This means that the physical processes and mechanisms that regulate star formation and its termination in galaxies in the early universe may have to be revisited,” – Andrea Weibel
Such extraordinary efficiency brings to the fore the question of when stars formed and when they became quiescent in those massive galaxies. RUBIES-UDS-QG-z7 formed an incredible 15 billion solar masses in stars. It also and quite unexpectedly stopped the creation of new stars much sooner than scientists thought would happen.
“We discovered a galaxy which formed 15 billion times the mass of the sun in stars and then stopped forming stars before the universe was only 700 million years old,” – Andrea Weibel
This discovery emphasizes that large galaxies, like RUBIES-UDS-QG-z7, had a short window in which to complete their star formation. Their ancestors clearly needed to mutate swiftly and successfully in order to do so.
The Rarity of RUBIES-UDS-QG-z7
RUBIES-UDS-QG-z7 is among the rarest objects identified in JWST observations, with only one such galaxy found across all analyzed data. Nearly all massive galaxies we detect from this epoch have prominent emission lines. They frequently show indications of obscured active galactic nuclei (AGN), which can further bias the detection of light.
“So far, we have only found one such object in all the JWST data that we investigated,” – Andrea Weibel
The lack of such indicators for an AGN in RUBIES-UDS-QG-z7 makes it highly likely that its light is provided solely by stars. This directly rules out the existence of accreting supermassive black holes. This distinction deepens the significance of RUBIES-UDS-QG-z7 and its implications for understanding galaxy evolution.
“Massive galaxies observed early in the universe only had a very limited amount of time to form their stars,” – Andrea Weibel
The uniqueness of RUBIES-UDS-QG-z7 not only enriches the understanding of early galaxy formation but prompts further investigation into how similar galaxies might have evolved under different conditions.
Implications for Future Research
The finding of RUBIES-UDS-QG-z7 pushes back the time-line for massive quiescent galaxies by another 500 million years. This unexpected conclusion highlights the importance for experts studying astronomy to recalibrate established models and paradigms of galaxy formation and evolution.
“This makes RUBIES-UDS-QG-z7 the most distant massive quiescent galaxy known to date,” – Andrea Weibel
This find is a discovery of broad significance well beyond one galaxy. More broadly, it should push us to reconsider the mechanisms of star formation in galaxies over the full breadth of cosmic time. The research team has continued to focus on understanding how these massive galaxies formed and prematurely quenched. This information has the potential to revolutionize existing astronomical theories.
“RUBIES-UDS-QG-z7, however, is not only massive but has already stopped forming stars 50 to 100 million years before we observe it, while normal galaxies at these epochs are still building up their stellar mass through star formation,” – Andrea Weibel
