TFA says &quot;they had heard and recorded the sound of two black holes colliding a billion light-years away&quot; and &quot;1.2 billion years ago&quot;.<p>And from the paper: &quot;The source lies at a luminosity distance of 410+160-180 Mpcc corresponding to a redshift z=0.09+0.03-0.04.&quot;. (<a href="https:&#x2F;&#x2F;dcc.ligo.org&#x2F;LIGO-P150914&#x2F;public" rel="nofollow">https:&#x2F;&#x2F;dcc.ligo.org&#x2F;LIGO-P150914&#x2F;public</a>) Which corresponds to 1.337+0.522-0.587 billion ly (or between 750.2 million and 1.859 billion ly).