... As the Sun floods Comet Hyakutake with ultraviolet light gases in the coma scatter the radiation and fluoresce making the comet a bright source in the ultraviolet sky. ... The colors of Comet Hyakutake are caused by the action of sunlight on the dust and gas produced by the warming nucleus. ... NASA's Hubble Space Telescope captured this image of the near-nuclear region of Comet Hyakutake on March 25 as the comet approached within 9.3 million miles of the Earth. ... Near Comet Hyakutake's Nucleus . ...