Cloud 9, a massive accumulation of gas located 14 million light-years away, has emerged as the strongest candidate for a starless or “failed” galaxy ever discovered by humanity, according to a research team led by Ignacio Trujillo of the Instituto de Astrofísica de Canarias in Spain. While the object possesses a million solar masses of hydrogen gas and roughly 5 million solar masses of dark matter near the spiral galaxy Messier 94, observations using the Hubble Space Telescope and the Gran Telescopio Canarias reveal that it emits virtually no starlight.
The Hunt for Cloud 9 and Its Complete Lack of Starlight
Astronomers have theorized the existence of dark, starless galaxies for decades, but finding them has proven exceptionally difficult because they lack visible stars. According to Trujillo, speaking to Space.com, the most striking aspect of the research was the absolute emptiness of the image at the location of Cloud 9. When researchers looked at deep images where a structure containing a million solar masses of gas should reside, they saw nothing. Trujillo noted that while most objects in the universe leave some trace of light, Cloud 9 does not.
To investigate further, Trujillo and his colleagues utilized the HiPERCAM camera on the Gran Telescopio Canarias, the world’s largest optical telescope. This effort yielded optical images approximately ten times deeper than any previous views of the region achieved in just 2.36 hours of integration time. The results showed absolute zero stellar emission within the designated region. By assuming an old, metal-poor stellar population—which represents the hardest kind to detect—the researchers established an upper limit on the total stellar mass of just 16,000 solar masses, leaving Cloud 9 genuinely starless within observational limits.
Did you know? Starless galaxies are defined as systems possessing large amounts of gas and dust alongside massive dark matter halos, yet failing to cross the threshold required to ignite and sustain a significant stellar population.
Why Do Galaxies Fail to Form Stars?
Trujillo explained that the leading theoretical explanation involves the ultraviolet background radiation permeating the universe. Following the epoch of reionization, this radiation field heated the gas residing in low-mass dark matter halos to temperatures high enough that the gas could not cool efficiently and collapse to form stars.
Cosmological simulations predict that dark matter halos falling below a threshold of roughly 5 billion solar masses should remain essentially starless. Because Cloud 9 features a halo mass consistent with this specific regime, researchers suggest that starless galaxies are not exotic anomalies, but rather a natural and abundant prediction of standard cosmological models. The primary challenge facing astronomers has simply been locating them.
Future Prospects and Verification with the James Webb Space Telescope
Despite the clarity of the recent optical data, the scientific community is waiting for further investigation before definitively declaring Cloud 9 the first confirmed starless galaxy. Trujillo noted that deeper space-based imaging will prove particularly valuable because resolving individual stars helps bypass the various complications associated with diffuse-light measurements.
While the Hubble Space Telescope has provided exceptionally strong evidence, future facilities such as the James Webb Space Telescope (JWST) could potentially push the search much further. However, researchers emphasize that optimal filters and stellar tracers must be carefully chosen for those future observations. The team’s research has been made publicly available on the arXiv paper repository.
Pro Tip: Researchers looking into low-mass dark matter halos rely heavily on neutral hydrogen observed at radio wavelengths combined with deep optical imaging to rule out faint stellar components.
Frequently Asked Questions
What is a starless galaxy?
A starless galaxy is a cosmic structure that contains vast amounts of gas, dust, and dark matter, but lacks the stars and visible starlight typically found in traditional galaxies.
How far away is Cloud 9?
According to the research team, Cloud 9 is located 14 million light-years away near the spiral galaxy Messier 94 (M94).
Why haven’t scientists found starless galaxies before?
Because these objects lack stars, they produce no visible light, making them nearly impossible to find through traditional optical surveys without combining radio wavelength gas emissions with extremely deep optical imaging.
What are your thoughts on the discovery of Cloud 9? Could there be thousands of invisible, starless galaxies hiding in our cosmic neighborhood? Share your perspective in the comments below, and subscribe to our newsletter for the latest updates in space exploration and astrophysics.