The foundational milestone of modern multi-messenger astronomy. The coalescence of two neutron stars was detected in gravitational waves, followed 1.7 seconds later by a short gamma-ray burst (GRB 170817A) detected by Fermi-GBM and INTEGRAL, and subsequently identified across the entire electromagnetic spectrum in host galaxy NGC 4993 as kilonova AT 2017gfo.
| Observatory / Instrument | Spectral Regime | Observational Detection & Counterpart Findings |
|---|---|---|
|
Fermi GBM / INTEGRAL
|
Gamma-ray (10–1000 keV)
|
Detected GRB 170817A at Δt = +1.74s, confirming speed of gravity equals speed of light to 1 part in 10^15.
|
|
Swope 1m / Magellan
|
Optical (r, i, z)
|
Identified optical transient AT 2017gfo in NGC 4993 at 10.9 hours post-merger.
|
|
Chandra X-ray Observatory
|
X-ray (0.5–8 keV)
|
Off-axis relativistic jet afterglow detected at day 9, peaking around day 160.
|