A newly discovered dwarf galaxy called FAST J0139+4328 appears to be composed almost entirely of dark matter. The strange galaxy located just 94 million light-years away does not emit any optical light. The research has been accepted into The Astrophysical Journal Letters and is available on arXiv.
Dark matter is an essential component of most galaxies. It is believed to contribute to the coming together of stars, gas, and the rotating core of hot material, thus forming a galaxy. However, FAST J0139+4328 is challenging this idea.
This weird matter is the main explanation for the strange discrepancy between the amount of normal matter and the gravity needed to hold it together. Dark matter does not interact with normal matter except through gravity, and it does not emit detectable radiation.
However, the dark matter theory has problems. The main drawback is the discrepancy between the number of simulated dwarf galaxies and the observed dwarf galaxies. Although we may not yet have discovered some types of dwarf galaxies, such as those made mostly of gas and dark matter.
A few candidate dark galaxies have been identified, but they are very close to other structures. This makes them difficult to distinguish from masses of debris torn away by stronger gravitational forces. An ideal dark galaxy candidate would be adrift, isolated in space, where its identity could not be mistaken.
The discovery
To search for these galaxies, Jin-Long Xu and his team of astronomers used the Five Hundred Meter Aperture Spherical Radio Telescope (FAST) in China. They looked for radio emissions from large clouds of neutral atomic hydrogen (HI) gas in intergalactic space with characteristics consistent with a galaxy.
After an exhaustive search, they found FAST J0139+4328. The galaxy appears to be drifting on its own, making it an ideal candidate for a dark galaxy. Follow-up infrared and ultraviolet observations revealed some faint stars.
The findings provide evidence for the existence of isolated dark galaxies in the nearby Universe. In addition, they help us understand more about the presence of dark matter and its distribution in the universe.
Importance
In conclusion, the recent discovery is revolutionizing ideas about dark matter and its presence in galaxies. The existence of isolated dark galaxies in the nearby universe is an important piece of the puzzle in the quest to understand dark matter.
Surely other scientists will try to confirm the nature of the object. In which case, something different may turn out, as it did with a galaxy called Dragonfly 44.
In 2016 it was discovered that this galaxy was composed of 99.99% dark matter. However, four years later, astronomers determined that Dragonfly 44 was not so abnormal as human error in the calculations.