Astronomers Discover New Almost Dark Galaxy
Astronomers have discovered a new almost dark galaxy, dubbed "Nube." The galaxy is so faint that it is barely visible in optical light, but it is as massive as the Small Magellanic Cloud (SMC). This discovery, published on October 18, 2023 in the arXiv pre-print server, could help astronomers better understand the nature of dark matter and the formation of galaxies.
Nube was discovered serendipitously by an international team of astronomers while analyzing deep optical imagery from the IAC Stripe 82 Legacy Project. The galaxy has a very low surface brightness, meaning that it emits very little light per square unit of area. This makes it very difficult to detect in optical surveys, which is why it had remained hidden until now.
Despite its low surface brightness, Nube is a very massive galaxy. It has a stellar mass of about 390 million solar masses and a total halo mass of about 26 billion solar masses. This means that Nube is dominated by dark matter, which makes up about 99.9% of its mass.
Nube is also the most extended and massive almost dark galaxy ever discovered. It is 10 times fainter and has a radius three times larger than typical ultra-diffuse galaxies (UDGs) with similar stellar masses. This suggests that Nube is a unique type of galaxy that could provide new insights into the formation and evolution of galaxies.
The discovery of Nube raises a number of questions about the nature of almost dark galaxies and their role in the early universe. For example, astronomers are not sure how these galaxies form or how they are able to retain so much dark matter. Nube could also help astronomers better understand the relationship between dark matter and baryonic matter, which is the type of matter that makes up stars, planets, and other visible objects in the universe.
Further studies of Nube and other almost dark galaxies could help astronomers answer these questions and shed new light on the mysterious nature of dark matter.