The approximate angular width of the jet ( that is , the degree of beaming ) can be estimated directly by observing `` jet breaks '' in afterglow light curves : a time after which the slowly-decaying afterglow begins to fade suddenly , as the jet slows down and can no longer beam its radiation so effectively . The approximate angular width of the jet ( that is , the degree of beaming ) can be estimated directly by observing `` jet breaks '' in afterglow light curves : a time after which the slowly-decaying afterglow abruptly begins to fade rapidly as the jet slows down and can no longer beam its radiation as effectively .