Astronomers spot an unexpected 'ghostly object' in space

Researchers report a starless, gas-rich dark matter cloud called Cloud-9 about 14 million light-years away; Hubble observations show it contains no stars. The object matches a predicted class called Reionization-Limited H I Clouds (RELHICs) and may illustrate a halo that failed to form a galaxy.

Astronomers report the detection of a starless, gas-rich dark matter cloud nicknamed Cloud-9, located about 14 million light-years from Earth. The object was initially identified in radio data from China's FAST telescope and later observed with the Hubble Space Telescope, which found no stars in the cloud. Researchers describe it as a Reionization-Limited H I Cloud (RELHIC), a predicted type of dark-matter-dominated structure that did not ignite star formation. The finding is presented as a nearby example of a primordial building block that never became a luminous galaxy. Key facts: - Cloud-9 is starless and gas-rich and lies roughly 14 million light-years away. - Its central region is a compact sphere of neutral hydrogen about 4,900 light-years across. - Radiation from the gas implies a hydrogen mass near one million times the Sun's mass. - To remain bound at that size, the team estimates the cloud requires roughly five billion solar masses of dark matter. - The cloud was first seen by FAST about three years ago; Hubble follow-up confirmed the absence of stars. - The object fits the RELHIC category and the results were published in The Astrophysical Journal Letters and discussed at an American Astronomical Society meeting. Summary: The discovery provides an observational example of a dark-matter-dominated structure that appears to lie below the threshold needed for star formation, helping test theories about the minimum halo mass for galaxy formation. The research team reports they are searching for additional RELHIC candidates to determine whether Cloud-9 is representative or unusual, and further observations were noted as the next step.