Short Wave A failed galaxy could solve the dark matter mystery
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Jan 21, 2026 
Andrew Fox and Gagandeep Anand, both astronomers at the Space Telescope Science Institute, dive into the fascinating world of dark matter. They explore Cloud 9, a unique starless dark matter halo that could be pivotal in understanding dark matter. The discussion covers how Hubble's observations revealed Cloud 9's emptiness, the implications for galaxy formation, and its potential to refine the Lambda-CDM theory. They emphasize the importance of finding more starless halos to unlock further secrets of the universe.
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Starless Dark Matter Halo Observed
- Cloud 9 is a dark matter halo with gas but virtually no stars, a predicted but previously unobserved object.
- Observing it provides direct confirmation that some halos never formed galaxies, as lambda-CDM predicts.
Hubble Surprise: No Stars Found
- Andrew (Andy) Fox expected to find stars in the Hubble images of the cloud near M94 but found none even after long exposures.
- The blank, starless result surprised the team and signaled the object is a different class of gas-rich, star-poor system.
Lambda-CDM Predicts Failed Galaxies
- Galaxies form inside dark matter halos, but lambda-CDM predicts many halos are too small to form stars.
- Cloud 9 fits that prediction: a relic halo below the critical mass for galaxy formation.