= Bondi mass
{c}
{title2=$M_B$}
The <Bondi mass> measures the total mass-energy remaining in an <isolated system> at a <retarded time>, as defined at <future null infinity>. It is obtained by integrating the <Bondi mass> aspect over a sphere, with normalization set by the <metric> convention.
Outgoing <gravitational radiation> carries <energy> away, so the <Bondi mass> decreases by a nonnegative news-squared <flux> in the vacuum mass-loss formula. Additional outgoing matter contributes its own <flux>. This is distinct from the <ADM mass> defined at <spatial infinity>: the two quantities use different asymptotic cuts and account differently for <radiation> that has escaped.<Bondi-Sachs Formalism by Thomas Mädler and Jeffrey Winicour>[§3, mass aspect and Bondi mass-loss formula]{ref}
Back to article page
