When astronomers observed the comet Schwassman - Wachmann 3 becoming 1, 000 times brighter in September 1995, they correctly hypothesized that its increased brightness was a result of the comet' s breaking up -- when comets break up, they emit large amounts of gas and dust, becoming visibly brighter as a result
However, their observations did not reveal comet Schwassman-Wachmann 3 actually breaking into pieces until November 1995, even though telescopes were trained on it throughout the entire period
Comets often do not emit gas and dust until several weeks after they have begun to break up.