Astronomers using the Hubble Space Telescope have discovered a fascinating new cosmic object, a cloud of dark matter and gas without any stars. This cloud, located about 14 million light-years from Earth in the spiral galaxy Messier 94, has been aptly nicknamed “Cloud 9.”
Scientists are excited about Cloud 9 because it could help explain how galaxies formed in the early universe. Andrew Fox from the Space Telescope Science Institute (AURA/STScI) calls it “a window into the dark universe.” Dark matter makes up around 85% of the universe, yet it’s hard to detect since it doesn’t emit light. Instead, its presence is inferred from its gravitational interactions with regular matter.
Dark matter has significantly influenced the universe’s structure, guiding the formation of stars and galaxies. Cloud 9 is a type of dark matter cloud known as a Reionization-Limited Hydrogen I Cloud (RELHIC), where hydrogen gas is expected to accumulate, usually leading to star formation. However, that hasn’t happened yet in Cloud 9, likely due to insufficient gas.
Team leader Alejandro Benitez-Llambay from Milano-Bicocca University described Cloud 9 as “a tale of a failed galaxy.” He emphasized that sometimes scientists learn more from failures than successes. The absence of stars in this case supports the theory about galaxy formation.
Before this discovery, scientists theorized about RELHICs, but it took Hubble’s advanced technology to prove their existence. Gagandeep Anand of STScI noted, “With Hubble, we can see that there’s nothing there.” This underscores how vital Hubble is in astronomy, revealing aspects of the universe that ground-based telescopes cannot.
Interestingly, the study of Cloud 9 also points to the possibility of many more “abandoned houses” in the cosmos, according to team member Rachael Beaton. Unlike other hydrogen clouds studied near the Milky Way, Cloud 9 is smaller and more compact, measuring about 4,900 light-years across and holding roughly 1 million solar masses. However, it boasts an estimated 5 billion solar masses of dark matter.
The hope is that Cloud 9 may one day evolve into a fully-fledged galaxy, but it needs to gather more hydrogen gas to spark star formation. For now, its lack of stars gives scientists a rare chance to study dark matter clouds without interference from stars.
As researchers continue to analyze data from Hubble, they are eager to uncover more RELHICs. This discovery enriches our understanding of the universe’s origins and offers a fascinating glimpse into ongoing cosmic processes.
The study on Cloud 9 was published in The Astrophysical Journal Letters and presented at the 247th meeting of the American Astronomical Society in Phoenix.
