Light Bridges on the Sun . ... SVST Explanation: Bridges the length of a planet can form on the Sun in a matter of hours. Known as light bridges , these structures may form as large sunspot groups decay. Above , one of the sharpest photographs of the Sun ever taken shows two such light bridges that appeared late last month. The 5000-kilometer long bridges connect moderately dark penumbral regions across the cool abyss of two dark sunspot umbras . ... NASA Official: Jay Norris. ...