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B. P. Abbott, R. Abbott, T. D. Abbott | Physical Review Letters | (2017)
Primary Link Archive DOI Openalex Full text (OA)

Key Takeaways

Plain English Takeaway

Scientists detected ripples in space from two neutron stars crashing together, and saw a burst of light soon after. This proved these cosmic crashes make both gravitational waves and short bursts of gamma rays.

Study Aim

The paper aims to report the first direct observation of gravitational waves (ripples in space-time) from the merger of two neutron stars (extremely dense collapsed stars). The authors seek to measure the properties of this event, connect it to a short gamma-ray burst (a sudden flash of high-energy light), and show that such mergers are the source of these bursts. Simply put: The study set out to catch and explain the signals from two neutron stars smashing together, and to show these events also make bright flashes of light.

Study Design

The research used the Advanced LIGO and Advanced Virgo detectors, which are large instruments that sense tiny changes in distance caused by passing gravitational waves. On August 17, 2017, these detectors picked up a strong signal lasting about 100 seconds, which matched the expected pattern from two neutron stars spiraling together. The team analyzed the data, removed noise, and compared the signal to computer models to estimate the masses and spins of the stars. They also checked for light signals from the same spot in the sky, finding a gamma-ray burst and other electromagnetic signals soon after. Simply put: Scientists used special detectors to listen for space ripples from colliding stars, then checked if telescopes saw a flash of light from the same place.

Findings

The study reveals that the gravitational-wave event GW170817 came from two neutron stars with masses between about 1.17 and 1.60 times the mass of the Sun. The event was located about 40 million parsecs (about 130 million light-years) away, making it the closest and best pinpointed gravitational-wave source so far. Just 1.7 seconds after the merger, a short gamma-ray burst was detected from the same region, confirming that such bursts are caused by neutron star mergers. Follow-up observations across the electromagnetic spectrum further supported this. The results provide new information about the properties of neutron stars, the rate of such mergers, and allow new tests of gravity and measurements of the universe's expansion. Simply put: The team proved that crashing neutron stars make both space ripples and bright flashes, helping us learn more about these stars and the universe.

Abstract

On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mrow><a:mn>8.0</a:mn><a:mo>×</a:mo><a:msup><a:mrow><a:mn>10</a:mn></a:mrow><a:mrow><a:mn>4</a:mn></a:mrow></a:msup></a:mrow><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi>years</a:mi></a:mrow></a:math>. We infer the component masses of the binary to be between 0.86 and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mn>2.26</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:msub><c:mrow><c:mi>M</c:mi></c:mrow><c:mrow><c:mo stretchy="false">⊙</c:mo></c:mrow></c:msub></c:mrow></c:math>, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mrow><f:mn>1.17</f:mn><f:mi>–</f:mi><f:mn>1.60</f:mn><f:mtext> </f:mtext><f:mtext> </f:mtext><f:msub><f:mrow><f:mi>M</f:mi></f:mrow><f:mrow><f:mo stretchy="false">⊙</f:mo></f:mrow></f:msub></f:mrow></f:math>, with the total mass of the system <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mrow><i:mn>2.7</i:mn><i:msubsup><i:mrow><i:mn>4</i:mn></i:mrow><i:mrow><i:mo>−</i:mo><i:mn>0.01</i:mn></i:mrow><i:mrow><i:mo>+</i:mo><i:mn>0.04</i:mn></i:mrow></i:msubsup><i:msub><i:mrow><i:mi>M</i:mi></i:mrow><i:mrow><i:mo stretchy="false">⊙</i:mo></i:mrow></i:msub></i:mrow></i:math>. The source was localized within a sky region of <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:mrow><l:mn>28</l:mn><l:mtext> </l:mtext><l:mtext> </l:mtext><l:mrow><l:msup><l:mrow><l:mi>deg</l:mi></l:mrow><l:mrow><l:mn>2</l:mn></l:mrow></l:msup></l:mrow></l:mrow></l:math> (90% probability) and had a luminosity distance of <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:mrow><n:mrow><n:mn>4</n:mn><n:msubsup><n:mrow><n:mn>0</n:mn></n:mrow><n:mrow><n:mo>−</n:mo><n:mn>14</n:mn></n:mrow><n:mrow><n:mo>+</n:mo><n:mn>8</n:mn></n:mrow></n:msubsup><n:mtext> </n:mtext><n:mtext> </n:mtext></n:mrow><n:mrow><n:mi>Mpc</n:mi></n:mrow></n:mrow></n:math>, the closest and most precisely localized gravitational-wave signal yet. The association with the <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline"><p:mi>γ</p:mi></p:math>-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline"><r:mi>γ</r:mi></r:math>-ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology. Published by the American Physical Society 2017

Referenced In

StarTalk

Season 17, Episode 33: Gravitational Waves from Colliding Neutron Stars

Hey StarTalkians! Episode 33 of Season 17 was another Cosmic Queries edition, with Neil and Negin working through a grab-bag of questions covering everything from LIGO to lycanthropy. One interesting question asked about visible sources of gravitational waves:

Cosmic Queries – LIGO, Light, & Lycanthropy - StarTalk Radio

(from 34:00)

Neil addressed this question very well, but after the excitement of the famous first gravitational wave observation, this “visible” result got comparatively little attention.  

The GW170817 Observation: Seeing the Source

Neil’s answer is based on the GW170817 observation in August 2017. The LIGO and Virgo gravitational wave detectors picked up a signal consistent with two in-spiralling neutron stars.

This is kind of fitting, because the first indirect evidence of gravitational waves came from a binary neutron star system.

Neutron stars aren’t particularly massive – around 1.4-times the mass of the sun – but they are incredibly compact, crammed into a radius of just 10 km or so. If the Earth was shrunk until it was as dense a neutron star, it would end up just 305 meters in diameter.

Observations of two neutron stars orbiting closely showed a decrease in orbital energy, which physicists assumed was a sign of gravitational wave emission.

The GW170817 observation corroborates this. Two US-based LIGO detectors made the observation, and the Virgo detector in Italy helped localize the source. Such binary neutron star mergers also create gamma-ray bursts, and right around that time, NASA’s Fermi space telescope spotted a matching burst.

It’s like hearing a siren from inside your apartment. You know there’s an emergency somewhere, but you don’t know the exact source until you follow the sound and locate the flashing light.  

How Pulsars Can Become the Detector

While checking into Neil’s comment, something else incredibly cool came up. Other researchers used pulsar signals to detect gravitational waves in a different way. Pulsars are neutron stars that give off regular flashes, like a lighthouse whipping around and periodically pointing at you. They’re like cosmic clocks.

Tracking 25 pulsars, researchers looked for slight variations in the timing of the pulses, a sign of disturbance by a gravitational wave. Like a spider waiting for vibrations along its web, they were able to detect a gravitational wave background. These were probably created by binary black hole systems.

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Jun 6, 2026 1:30 PM

This is really cool, and mind-bending! Let's see if I understood this correctly.

So we had first detected gravitional waves in 2015. And then in 2017, we detected not just the gravitional waves, but also a burst of electromagnetic waves (light) from the same event (merger)?

Help me out here: what is the broader significance of this observation? Is it just the ability to study the light burst, similar to how we study the results from particle accelerators?

Thank you!