The Hubble Space Telescope has captured images of a rare celestial object, an ultra-diffuse galaxy (UDG) known as “Cloud-9,” which is dominated by dark matter. The findings were recently published in the Astrophysical Journal Letters.
Ultra-diffuse galaxies are faint, extended objects that are as large as the Milky Way but have only a fraction of its stars. This results in them being extremely dim and difficult to detect. The galaxy Cloud-9, officially known as UGC 2162, is located about 240 million light-years away in the constellation of Aries.
The observations made by Hubble have provided astronomers with new insights into the nature of these elusive galaxies. Cloud-9 stands out among UDGs because of its unusually large size and low surface brightness. Its diffuse nature implies that the stars within it are spread out over a large area, making it appear faint and ghostly.
Despite its faint appearance, Cloud-9 is dominated by dark matter. While the visible matter in the galaxy (i.e., stars and gas) accounts for a small fraction of its total mass, the rest is made up of dark matter. Dark matter, an invisible form of matter which does not interact with light or other forms of electromagnetic radiation, is believed to make up about 85% of the matter in the universe. However, its exact nature remains one of the biggest mysteries in modern cosmology.
UDGs like Cloud-9 are an excellent laboratory for studying dark matter due to their high dark matter content. By studying the motions of these galaxies, astronomers can infer the distribution of dark matter within them. The Hubble data suggests that Cloud-9 is a failed galaxy, meaning it has stopped forming new stars due to a lack of gas. This is likely due to the strong tidal forces from the nearby massive galaxy cluster Abell 1367, which could have stripped away much of Cloud-9’s gas.
The fact that Cloud-9 has remained intact despite these strong tidal forces also provides clues about the nature of dark matter. The high concentration of dark matter within Cloud-9 could have acted as a gravitational glue, keeping the galaxy together.
Finally, the study of UDGs can also provide valuable information about galaxy formation and evolution. By understanding why some galaxies fail to form stars, researchers can gain insight into the processes that lead to the formation of galaxies like our own Milky Way. The observations of Cloud-9 by Hubble have thus contributed significantly to our understanding of these mysterious celestial objects.
Source link