Cloud-9 Discovery Reveals New Class of Dark-Matter-Dominated Objects

Astronomers have reported the identification of Cloud-9, a previously unknown type of astronomical object dominated by dark matter and lacking stars, using the Hubble Space Telescope. This finding contributes to the study of early galaxy formation and the composition of the Universe.

Cloud-9 is classified as a Reionization-Limited H I Cloud, or RELHIC, which is a neutral hydrogen structure from the early Universe that never developed stars. The object is situated close to the spiral galaxy Messier 94, at a distance of approximately 14 million light-years from Earth.

The detection of Cloud-9 was first achieved through a radio survey conducted by China’s FAST telescope. Subsequent observations by the Green Bank Telescope and the Very Large Array confirmed its existence before Hubble’s imaging established the absence of stars within the object.

Lead author Gagandeep Anand from the Space Telescope Science Institute stated that Hubble’s sensitivity was essential in confirming that Cloud-9 contains no stars, which ruled out the possibility of it being a faint dwarf galaxy. The object’s neutral hydrogen extends about 4,900 light-years and has a mass close to one million times that of the Sun.

What the numbers show

• Cloud-9 is located roughly 14 million light-years from Earth
• The neutral hydrogen spans about 4,900 light-years
• Total mass estimated at five billion solar masses

Analysis of Cloud-9’s gravitational equilibrium indicates a total mass of around five billion solar masses, suggesting that dark matter is the dominant component. This mass is much greater than what would be expected from its hydrogen content alone.

Alejandro Benítez-Llambay of the University of Milano-Bicocca described Cloud-9 as a “failed galaxy” and a primordial structure that never underwent star formation. The object’s properties provide a reference point for understanding early cosmic building blocks that did not evolve into typical galaxies.

Andrew Fox, representing AURA/STScI for the European Space Agency, said that Cloud-9 offers astronomers an uncommon opportunity to study regions of the Universe where dark matter is the primary influence. Observations of such objects can inform models of cosmic structure and the processes that shaped the early Universe.

The identification and study of Cloud-9 highlight the combined capabilities of radio and optical telescopes in revealing hidden components of the cosmos. The discovery adds to the catalogue of objects that help trace the evolution of galaxies and the distribution of dark matter in the Universe.

* This article is based on publicly available information at the time of writing.