FAST telescope discovers two starless hydrogen clouds near Whirlpool galaxy

Astronomers using China’s Five‑hundred‑meter Aperture Spherical Telescope (FAST) have identified two massive clouds of hydrogen gas in the vicinity of the Whirlpool galaxy (M51). Each cloud contains roughly three million solar masses of neutral hydrogen, as measured through the 21‑centimetre emission line, but shows no detectable optical counterpart in existing surveys. The findings, detailed in a paper published in *Astronomy & Astrophysics* on August 4, describe the clouds as “almost star‑less,” a characteristic that distinguishes them from typical galactic structures where gas and stars coexist.

The discovery adds to a small but growing list of hydrogen‑rich, optically dark objects that may represent a transitional stage in galaxy formation or remnants of tidal interactions with M51. Because the clouds lack observable starlight, further multi‑wavelength observations will be required to determine their composition, dynamics, and relationship to the nearby spiral galaxy. Researchers anticipate that follow‑up studies with both radio and deep optical facilities could clarify whether these structures are nascent dwarf galaxies, tidal debris, or a new class of dark hydrogen clouds.