On what date did LIGO record the gravitational-wave signal?

On what date did LIGO record the gravitational-wave signal?

• A. September 15, 2015
• B. September 14, 2015
• C. August 11, 2015
• D. September 15, 2016

Answer: (A)

Key idea: the date tied to this gravitational-wave discovery is encoded in the event name and the actual timestamp of the detection. The first gravitational-wave signal from a binary black hole merger was recorded by LIGO on September 14, 2015, at about 09:50:45 UTC. The event is named GW150914 to reflect the year 2015 and the date 09-14. This short chirp, lasting roughly 0.2 seconds and sweeping from about 35 Hz up to 150 Hz, was observed by both LIGO detectors, confirming the astrophysical origin. That makes September 14, 2015 the correct date. The confusion with a different date often comes from later public alerts or naming conventions, but the actual recording happened on the 14th.

Key idea: the date tied to this gravitational-wave discovery is encoded in the event name and the actual timestamp of the detection. The first gravitational-wave signal from a binary black hole merger was recorded by LIGO on September 14, 2015, at about 09:50:45 UTC. The event is named GW150914 to reflect the year 2015 and the date 09-14. This short chirp, lasting roughly 0.2 seconds and sweeping from about 35 Hz up to 150 Hz, was observed by both LIGO detectors, confirming the astrophysical origin.

That makes September 14, 2015 the correct date. The confusion with a different date often comes from later public alerts or naming conventions, but the actual recording happened on the 14th.