Black Hole Collision Calculator

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Solar masses are the standard unit in gravitational-wave astronomy. Switch to kilograms for laboratory-scale comparisons.
The primary (larger) black hole mass. The first LIGO detection GW150914 had a primary of about 36 solar masses.
M☉
The secondary (smaller or equal) black hole mass. GW150914 had a secondary of about 29 solar masses.
M☉
Final black hole massHeavy stellar-mass black hole
61.54M☉

Mass remaining after gravitational-wave energy is radiated away

Chirp mass28.1M☉
Energy radiated (gravitational waves)3.463M☉c²
Energy radiated6,190.617×10⁴⁴ J
Event horizon radius (BH 1)106.34km
Event horizon radius (BH 2)85.66km
Event horizon radius (final)181.77km
Event horizon growth-0.1%
Peak inspiral frequency (ISCO)67.6Hz
Ringdown frequency169.9Hz
Final mass (M☉)61.54
Energy radiated (M☉ equiv)3.463
Chirp mass (M☉)28.1
Before merger192
After merger181.77

Horizon growth: -0.1%

  • BH 1 radius (km)
  • BH 2 radius (km)

A 36.0 + 29.0 M☉ merger leaves a 61.5 M☉ black hole.

  • About 5.3% of the total mass (3.46 M☉ = 6190.62 ×10⁴⁴ J) is radiated as gravitational waves - more power than all the stars in the observable universe emit in the same instant.
  • The inspiral chirps up to about 68 Hz at the ISCO, then the merged black hole rings down near 170 Hz.
  • The final event horizon radius is 181.8 km - comparable to a city, yet containing 61.5 solar masses.
  • A gravitational-wave observatory would measure a chirp mass of 28.10 M☉, the combination of m1 and m2 that drives the waveform frequency evolution.

Next stepThe peak frequency falls in LIGO's sensitive band (10-2000 Hz), so this merger would be detectable by ground-based observatories at cosmic distances.

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