Some galaxies that should have ceased forming stars long ago are defying expectations. A new theory proposes the existence of a third galactic category — red star-forming galaxies — which could transform current models of galaxy evolution and star formation. This idea, introduced by Charles Steinhardt, an astrophysicist at the University of Missouri, suggests that the universe may have birthed far more stars than previously believed.
Redefining How Galaxies Are Classified
For decades, astronomers have classified galaxies into two main types: blue galaxies, which are young and teeming with star formation, and red galaxies, considered old and inactive. But new observations challenge this binary view. Steinhardt‘s hypothesis introduces a compelling third category: galaxies that are red in appearance but continue to form stars.
“Red star-forming galaxies primarily produce low-mass stars, making them appear red despite ongoing star birth,” he explains.
Universe-wide Implications for Star Formation
The study, published in the Astrophysical Journal, shows that the consequences of this new classification go far beyond galactic naming conventions. These red star-forming galaxies could account for a significant portion of the stellar mass observed today, meaning previous estimates of star formation in the early universe may have been too low.
“This theory was developed to address inconsistencies with the traditional observed ratios of black hole mass to stellar mass and the differing initial mass functions in blue and red galaxies — two problems not explainable by aging or merging alone,” Steinhardt notes.
“However, what we learned is that most of the stars we see today might have formed under different conditions than we previously believed.”
What Happens After Starbursts?
A particularly puzzling class of galaxies known as post-starburst galaxies might also be reinterpreted under this framework. These are galaxies that experience a short but intense period of star formation, then suddenly go quiet.
Previously thought to be the aftermath of galactic mergers, Steinhardt now proposes another explanation. Rather than rapidly forming and then stopping, these galaxies may have simply been forming small, red stars all along.
According to SciTechDaily, “if that’s true, we may need to change how we define post-starburst galaxies, as some might belong to a different category of red star-forming galaxies.”
New Data, New Questions
The new theory is still in early stages, but upcoming research aims to test its predictions. At the University of Missouri, student-led projects are already underway. Junior Mathieux Harper and a team of undergraduates are working to find additional evidence that could support Steinhardt’s claims.
Meanwhile, sophomores Carter Meyerhoff and Zach Borowiak are analyzing data from the European Space Agency’s Gaia satellite, which has mapped over two billion stars in the Milky Way.
A New Chapter in the Story of the Universe
The notion of red galaxies still actively forming stars fundamentally alters how scientists view the life cycle of galaxies.
“The existence of these galaxies could mean that the universe has formed significantly more stars than previously estimated,” Steinhardt concludes. “It supports the idea that the life cycle of galaxies is more complex than a simple progression from blue to red and dead.”
If this third type of galaxy is confirmed, astronomy may soon rewrite large portions of cosmic history — and with it, our understanding of how the universe came to look the way it does.
Be First to Comment