For comparison , 7 Iris never comes closer than 0.85 AU and 4 Vesta never closer than 1.13 AU when it becomes visible to the naked eye in a pollution-free sky . For comparison , 7 Iris never comes closer than 0.85 AU and 4 Vesta never closer than 1.13 AU ( when it becomes visible to the naked eye in a light pollution-free sky ) .