Astronomers Unveil ‘Cloud-9’: A Potential Dark Matter Discovery

Astronomers have identified a newly discovered celestial object, referred to as “Cloud-9,” which may offer critical insights into the elusive nature of dark matter. This groundbreaking discovery, detailed in a recent publication in The Astrophysical Journal Letters, suggests that Cloud-9 could represent a dark matter cloud, potentially a remnant from the early universe. Dark matter is believed to constitute approximately 85 percent of the universe’s total matter, although it has never been directly observed.

According to study coauthor Andrew Fox, an astronomer at the Space Telescope Science Institute in Baltimore, Cloud-9 presents a unique opportunity to examine the dark universe. Fox emphasized, “We know from theory that most of the mass in the universe is expected to be dark matter, but it’s difficult to detect this dark material because it doesn’t emit light. Cloud-9 gives us a rare look at a dark-matter-dominated cloud.”

Theoretical frameworks suggest that dark matter originated from the Big Bang, which occurred approximately 13.8 billion years ago. It is thought to form cosmic clouds that lack the necessary gas to ignite star formation. Observations made with the Hubble Space Telescope confirmed that Cloud-9 is devoid of stars, reinforcing its classification as a failed galaxy.

“This is a tale of a failed galaxy,” noted study coauthor Alejandro Benitez-Llambay, an astrophysicist and assistant professor at the University of Milano-Bicocca in Milan, Italy. “In science, we usually learn more from failures than from successes. In this case, seeing no stars is what proves the theory right. It tells us that we have found in the local universe a primordial building block of a galaxy that hasn’t formed.”

The journey to uncovering Cloud-9 began three years ago during a survey of hydrogen gas near the spiral galaxy Messier 94, utilizing the Five-hundred-meter Aperture Spherical Telescope (FAST) located in China’s Guizhou province. Follow-up observations with the Green Bank Telescope and the Very Large Array confirmed the starless nature of the cloud.

Fox explained that theories of galaxy formation indicate there is a minimum threshold of dark matter needed to spark star formation. Cloud-9 represents an example of an object just below this threshold, containing no stars. The object received its nickname as it is the ninth gas cloud identified in proximity to Messier 94.

The core of Cloud-9 is composed predominantly of neutral hydrogen, spanning approximately 4,900 light-years in diameter. This distance is equivalent to about 5.88 trillion miles (or 9.46 trillion kilometers). The hydrogen mass within the cloud is estimated to be around 1 million times the mass of the Sun, with an additional 5 billion solar masses of dark matter contributing to its structure.

“There must be a massive amount of ‘invisible’ gravity holding it together,” stated study coauthor Dr. Rachel Beaton, an assistant astronomer at the Space Telescope Science Institute. She elaborated that the visible neutral hydrogen does not provide sufficient mass, implying a dark matter halo that offers the necessary gravitational support for the cloud.

Cloud-9 currently exists in a delicate balance, according to Beaton. “It has just enough mass to hold onto its gas, but not quite enough to force that gas into star formation,” she explained. This rarity may explain the limited number of similar objects observed in the local universe, as most halos either lose their gas entirely or evolve into full-fledged galaxies.

The future of Cloud-9 remains uncertain, as it may eventually accumulate more mass and transform into a galaxy, or it could lose mass if it approaches Messier 94, leading to its dissolution. Fox remarked, “If the cloud loses mass, it could happen if it falls closer in toward M94, and its gas gets stripped like a cloud in a wind tunnel until the cloud ceases to exist.”

Advanced observational techniques could provide pivotal insights into the core of Cloud-9, potentially revealing the quantity of dark matter contained within. Beaton highlighted that this could help narrow down the characteristics of dark matter particles using astrophysical data.

While Cloud-9 presents an intriguing case, it is not the first object discussed in connection with “dark galaxies.” Dr. Jacco van Loon, an associate professor of astrophysics at Keele University in England, cautioned against drawing definitive conclusions about Cloud-9’s nature without stronger evidence. He noted that another hydrogen cloud, FAST J0139+4328, was recently identified as a faint galaxy, suggesting that Cloud-9 could also harbor a similar unobserved structure.

The research team continues to search for additional objects like Cloud-9 to better understand whether it is an anomaly or part of a broader category of cosmic relics. Dr. Kristine Spekkens, a professor of astronomy at Queen’s University in Kingston, Ontario, remarked on the importance of ongoing investigations. “Further study of this starless gas, such as its unusual shape, will help unravel its origin as a starless galaxy or a free-floating cloud,” she stated.

As astronomers delve deeper into the mysteries of the universe, Cloud-9 stands as a compelling example of the potential discoveries awaiting in the vastness of space.