Hubble Image an evidence to dark matter

This undated image from the Hubble Space Telescope shows a ghostly ...

(Reuters) - This undated image from the Hubble Space Telescope shows a ghostly ring of dark matter in a galaxy cluster designated Cl 0024+17. Astronomers call the ring one of the strongest pieces of evidence to date for the existence of dark matter, an unknown substance thought to pervade the universe. Astronomers suggest that the ring was produced from a collision between two gigantic clusters. REUTERS/NASA, ESA, M.J. Jee and H. Ford/Johns Hopkins University/Handout (UNITED STATES). EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS.