Now, astronomers say they’ve discovered a new dwarf galaxy FCC 224. It appears to have no dark matter — that essential stuff long believed to make up most of the universe’s mass. In 2024, this major breakthrough was achieved by researchers. It was an extension of their regular effort to identify galaxies that lay outside the bounds of established cosmological models.
FCC 224 located about 65 million light-years away in the constellation Cetus. It’s studded with rich star fields, a dozen tightly bound clusters of stars that twinkle like diamonds strung on black silk. This galaxy hosts an abnormally rich population of star clusters considering its small size. This leads to the fascinating idea of how such galaxies formed and what exactly these galaxies are.
What makes FCC 224 special is the complete absence of dark matter. That’s a sign that this galaxy probably took a much less common evolutionary route than most galaxies. The two clusters in FCC 224 recede from each other very gradually. This absence of speed suggests they are not under the influence of the dark matter gravitational tug that is so characteristic of other galaxies at all. Evidence from the slow movement bolsters the theory that FCC 224 originated from a high-velocity collision of two galaxies. Notably, this collision was probably between gas-rich galaxies.
Interestingly, FCC 224 is not the only cosmic interloper in its galactic neighborhood. Its companion galaxy, FCC 240, has a similar size, shape, and orientation. Their close proximity and interactions with each other suggest they may have similar properties. This strongly advocates for FCC 224’s formation to be related to collision events occurring in its galactic environment.
Maria Buzzo, a doctoral candidate in astrophysics at Swinburne University of Technology, is the one who spearheaded the study of FCC 224. Her team compared data they had collected at the Keck Observatory in Hawaii. Using HST and ground-based telescopes, they closely tracked the movement and characteristics of its star clusters. Buzzo is keen to highlight what a landmark discovery this is for the study of dark matter-deficient galaxies.
“FCC 224 serves as a crucial data point in our effort to identify and study other dark-matter-deficient galaxies,” – Maria Buzzo
This finding of FCC 224 is consistent with other recent observations of galaxies that seem to be void of dark matter. This includes two enigmatic transients found within the NGC 1052 group of galaxies. This galaxy group is located about 65 million light-years away. That distance does deepen the mystery because it strengthens the impression that these galaxies may in fact be a more typical kind of dwarf galaxy than we previously thought.
Buzzo acknowledges how difficult this find makes things for the current models of galaxy formation.
“No existing galaxy formation model within our standard cosmological paradigm can currently explain how this galaxy came to be,” – Maria Buzzo
Diving deeper into FCC 224 helps paint a new, more complex picture of galaxy formation. It looks at how important dark matter is in shaping these galaxies. With ample Tatooine-like moons and dark matter abound, astronomers are exploring the mysteries of this captivating dwarf galaxy. They hope to learn more about dark matter and the formation of galaxies.
