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yesterday

Hubble Confirms First Starless Dark-Matter Cloud, ‘Cloud-9,’ a Predicted RELHIC

Deep Hubble imaging ruled out even faint starlight, making the object a benchmark for testing dark matter physics.

A region of space mostly filled with background galaxies, with one prominent star at upper left. A large blob of purple haze occupies much of the field. Within the purple region, an unremarkable area is outlined with a dashed white circle.
Cloud-9 was spotted in this region of space, about 2,000 light-years from Earth.
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Overview

  • An international team reports Cloud-9 as the first confirmed Reionization-Limited H I Cloud, a long-predicted, starless relic of early galaxy formation.
  • The object lies about 14 million light-years from Earth near Messier 94 and shows a compact, nearly spherical neutral-hydrogen core roughly 4,900 light-years across.
  • Radio measurements indicate about 1 million solar masses of hydrogen, implying an enclosing dark-matter halo of roughly 5 billion solar masses to keep the gas bound.
  • Cloud-9 was first detected by China’s FAST radio telescope, confirmed by the Green Bank Telescope and the Very Large Array, and then verified as starless with Hubble’s Advanced Camera for Surveys.
  • The peer-reviewed results appeared in The Astrophysical Journal Letters and were presented at the AAS meeting, with outside experts urging deeper, higher-resolution follow-ups to exclude ultra-faint stars and to probe dark-matter models.