Historical research guide · 1133 · 2016

Observation of Gravitational Waves from a Binary Black Hole Merger

B. P. Abbott et al. · LIGO Scientific Collaboration · Virgo Collaboration

In one minute

On 14 September 2015, LIGO’s detectors in Louisiana and Washington recorded the same gravitational-wave signal 6.9 milliseconds apart. Its frequency rose from 35 to 250 hertz; peak strain was about 10⁻²¹. The collaboration matched the signal to general-relativity waveforms for two black holes spiralling together, merging, and leaving one rotating black hole. The inferred initial masses were about 36 and 29 solar masses; the final mass was about 62, with roughly three solar masses of mass-energy radiated as gravitational waves. A matched-filter search found a false-alarm rate below one event per 203,000 years. This was the first direct gravitational-wave detection and the first observed binary-black-hole merger. LIGO measured a tiny change in the relative lengths of perpendicular arms.

Connection

Chapter 4 teaches the metric tensor as the thing that says how far apart two events are, and the whole warp-drive argument is about changing it on purpose. This is the measurement that shows the metric is a physical, changeable quantity that human hardware can read: a passing wave lengthened one four-kilometre arm and shortened the other, and the instrument saw it. It is also the calibration point for chapter 16, because the same instrument class is what any future high-frequency gravitational-wave device would have to beat.

From the source

On 14 September 2015 at 09:50:45 UTC the LIGO Hanford and Livingston detectors observed the same transient gravitational-wave signal, sweeping upwards in frequency from 35 to 250 hertz with a peak gravitational-wave strain of 1.0 times ten to the minus twenty-one, matching the waveform general relativity predicts for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole.Abstract; Section II, Observation
The event was recovered with a matched-filter signal-to-noise ratio of 24 and a false alarm rate below one event per 203,000 years, a significance greater than 5.1 standard deviations; the independent generic-transient search, which uses no waveform model at all, found the same event as the strongest of the entire search at 4.6 standard deviations.Abstract; Section V A, Generic transient search; Section V B, Binary coalescence search
The source parameters are an initial black hole pair of 36 and 29 solar masses and a final black hole of 62 solar masses spinning at 0.67, at a luminosity distance of 410 megaparsecs and redshift 0.09, with 3.0 solar masses of mass-energy radiated as gravitational waves and a peak gravitational-wave luminosity of 3.6 times ten to the fifty-sixth ergs per second.Table I, Source parameters for GW150914; Section VI, Source discussion
A gravitational wave alters the interferometer arm lengths so that the measured difference is the strain amplitude times the four-kilometre arm length, and the instrument reaches that sensitivity by multiplying the light phase by a factor of 300 in resonant arm cavities, circulating 100 kilowatts in each arm, suspending 40-kilogram fused-silica test masses that are isolated from ground motion by more than ten orders of magnitude above ten hertz.Section III, Detectors
Three separate tests of the signal against general relativity in the strong-field, high-velocity regime found no evidence of disagreement, and assuming a modified dispersion relation the observation constrains the Compton wavelength of the graviton to be greater than ten to the thirteenth kilometres, a bound on the graviton mass below 1.2 times ten to the minus twenty-two electronvolts over c squared, improving on the binary-pulsar bound by a factor of about a thousand.Section VI, Source discussion
What to watch: the paper names its own next measurements. Advanced LIGO reaching design sensitivity would detect a binary like this one with three times higher signal-to-noise ratio, and Advanced Virgo, KAGRA and a possible third LIGO detector in India would extend the network and sharpen position reconstruction and parameter estimation.Section VII, Outlook

The way in

https://doi.org/10.1103/PhysRevLett.116.061102

Historical source-access record. This guide links to the original; it does not reproduce the paper text.

TEXT. Read in full on 2026-09-11 from the version of record, Physical Review Letters 116, 061102, as distributed on arXiv at 1602.03837. Reproduced below: the abstract and sections I to III, VI, VII and VIII, plus Table I. The four figures are not reproduced; the caption of Figure 1 is kept because it carries the arrival-time difference and the reconstruction overlap. Sections IV and V, which set out the detector-validation checks and the two search pipelines in detail, are summarised in the claims rather than carried in full. The extraction from PDF glued some words together and rendered the plus-or-minus credible intervals as run-together digits; word spacing has been restored and each interval is reset in plain notation as a value followed by its upper and lower bound in parentheses. No wording has been changed.

How to cite it

B. P. Abbott et al., LIGO Scientific Collaboration, Virgo Collaboration (2016) Observation of Gravitational Waves from a Binary Black Hole Merger doi:10.1103/PhysRevLett.116.061102

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