GW170817

GW170817: two neutron stars merging about 40 Mpc away, localized to 16 square degrees at 90%.

Arrived

2017-08-17

What merged

two neutron stars

Distance

40 ± 15 Mpc

Seen in light as

AT2017gfo, in NGC 4993

50% credible region

5.0 square degrees

90% credible region

16.2 square degrees

Two neutron stars spiralling together, felt as a wave 40 Mpc away and then seen — the only gravitational-wave source anyone has ever caught the light of. Eleven hours after the wave arrived, a new point of light was found in NGC 4993, inside the tightest part of this region. It is not drawn as a place because the wave did not come from one: this is the whole of what the detectors could say about where.

Those two areas are credible regions rather than a boundary: the smaller holds half the probability and the larger nine tenths, and the tenth left over really is outside it. There is no right ascension and declination here because there is none to give — open it in the app to see the patch itself.

GWTC-1 sky localization for GW170817 — LIGO Scientific Collaboration and Virgo Collaboration

Open it in Bhagol — opens the app if you have it, and this page if you do not.