Hubble Telescope Discovers First Starless Cloud Offering Insight Into Early Galaxy Formation

A groundbreaking discovery has emerged from the NASA/ESA Hubble Space Telescope, revealing a unique astronomical entity—a starless cloud rich in gas and dark matter. This object, dubbed “Cloud-9,” is a significant find as it marks the first confirmed instance of such a relic from the early stages of galaxy formation.

Principal investigator Alejandro Benitez-Llambay from Milano-Bicocca University in Milan highlighted the importance of the discovery, referring to it as a narrative of a “failed galaxy.” He emphasized that in scientific exploration, failures can often produce more insight than triumphs. In this case, the absence of stars within this cloud supports existing theories about its primitive nature, suggesting it serves as a remnant of a galaxy that never formed.

Team member Andrew Fox from AURA/STScI, representing the European Space Agency, noted that the discovery provides a rare glimpse into the elusive realm of dark matter, a key component of the universe that remains largely undetectable due to its lack of light emission. Cloud-9, classified as a Reionization-Limited H I Cloud (RELHIC), consists primarily of neutral hydrogen and represents what scientists believe to be a primordial cloud from the universe’s formative years—essentially a fossil that bears no stars.

Until Hubble’s advanced capabilities were applied to this cloud, scientists could only speculate about its existence. According to lead author Gagandeep Anand from the Space Telescope Science Institute in Baltimore, previous observations may have misclassified this object as a faint dwarf galaxy due to insufficient sensitivity from ground-based telescopes. However, Hubble’s detailed imaging allowed researchers to confirm that the cloud harbors no stars.

The discovery of Cloud-9 was unexpected, hinting at the potential for other similar structures nearby. Rachael Beaton from STScI remarked that among our galactic neighbors, there may be other abandoned remnants. Scientists believe RELHICs like Cloud-9 do not contain enough gas to trigger star formation, thus providing insights into the mechanisms behind early galaxy formation.

Measuring about 4,900 light-years in diameter, Cloud-9 is relatively compact and spherical compared to its larger, more irregular counterparts often found near the Milky Way. It contains roughly one million solar masses of hydrogen gas and is overwhelmingly dominated by dark matter, estimated at around 5 billion solar masses. This finding is significant as it emphasizes the importance of exploring gas and dark matter to achieve a comprehensive understanding of cosmic structures beyond the luminous stars.

The identification of such “failed galaxies” poses observational challenges due to their tendency to be outshone by nearby bright objects. Additionally, environmental influences like ram-pressure stripping can further diminish their presence in the universe. Cloud-9 was initially discovered during a radio survey conducted by the Five-hundred-meter Aperture Spherical Telescope (FAST) in China, a finding subsequently validated by U.S. telescopes including the Green Bank Telescope and Very Large Array.

Located in close proximity to the spiral galaxy Messier 94 (M94), Cloud-9 may potentially evolve into a galaxy if it accumulates sufficient mass. Its current status as a RELHIC places it in a delicate balance where it neither collapses into star formation nor dissipates entirely.

This astonishing discovery sheds light on the complexities of galaxy formation, contributes to our understanding of the early universe, and offers crucial insights into the enigmatic nature of dark matter. The findings related to Cloud-9 have been published in The Astrophysical Journal Letters, highlighting the potential for future research to uncover more of these intriguing cosmic relics and deepen our grasp of the universe’s structure and dynamics.