# Neutron Binary (DD-542)

> In a binary neutron star system, the stars lose orbital energy by emitting gravitational waves, ripples in spacetime predicted by Einstein's general relativity. Their orbits shrink and speed up until they collide and merge. The first such merger was detected in gravitational waves and light on August 17, 2017 (GW170817). The footage, credited to astronomhub, shows an animation of two neutron stars merging.

- Department: Space
- First published: 2025-04-13
- Last updated: 2025-04-13
- Permalink: https://detailenjoyer.com/case/neutron-binary/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## On the timeline

- **Aug. 17, 2017**: GW170817 neutron star merger detected

Full timeline: https://detailenjoyer.com/timeline/?case=neutron-binary

## Quick facts

- **DD-542-F01**: Binary neutron stars. _(Write-up · Exhibit A (System))_
- **DD-542-F02**: Gravitational waves. _(Write-up · Exhibit B (Energy loss))_

## Write-up

Two neutron stars in orbit slowly spiral together. Gravitational waves carry away their energy.

1. **System**: Binary neutron stars.
2. **Energy loss**: Gravitational waves.
3. **Theory**: General relativity.
4. **End**: Merger.
5. **Detected**: GW170817, 2017.

## Related case files

- [Black Hole Binary (DD-464)](https://detailenjoyer.com/case/black-hole-binary/): I linked another binary merger

## Reel vs. record

- **Note**: None needed.

## Video: Neutron Binary: Two Neutron Stars in Orbit Slowly Spiral Together

- Duration: 17.6 s · Published: 2025-04-13
- File: https://detailenjoyer.com/assets/videos/DIYyGV4xC1j.mp4

### Transcript

Did you know, when two neutron stars orbit each other in a binary system, they gradually spiral inward due to the emission of gravitational waves, ripples in space-time predicted by Einstein's theory of general relativity. As they lose energy, their orbital speed increases, and the distance between them shrinks until they collide and merge in a violent event. NOW YOU KNOW!

## Questions & answers

**Q: What carries energy away?**  
A: Spacetime. _(Source: Write-up · Exhibit A (System) · Wikipedia: Neutron star merger)_

**Q: Predicted by?**  
A: Relativity. _(Source: Write-up · Exhibit B (Energy loss) · Wikipedia: Neutron star merger)_

**Q: Orbit over time?**  
A: Inspiral. _(Source: Write-up · Exhibit C (Theory) · Wikipedia: Neutron star merger)_

**Q: End result?**  
A: Collision. _(Source: Write-up · Exhibit D (End) · Wikipedia: Neutron star merger)_

**Q: First detection?**  
A: GW170817. _(Source: Write-up · Exhibit E (Detected) · Wikipedia: Neutron star merger)_

## Sources

- [Wikipedia: Neutron star merger](https://en.wikipedia.org/wiki/Neutron_star_merger)

## Cite this case file

Easterling, Marcus. "Neutron Binary." The Detail Department (DetailEnjoyer), case file DD-542, last updated Apr 13, 2025. https://detailenjoyer.com/case/neutron-binary/