The basic physics of the binary black hole merger GW150914

TL;DR

This paper explains the GW150914 black hole merger detection using basic physics concepts, showing how the data reveals the inspiral and merger of two ~35 solar mass black holes and estimating their distance and energy radiated.

Contribution

It provides an accessible, physics-based analysis of the GW150914 signal consistent with complex relativistic models, emphasizing understanding from fundamental principles.

Findings

Black holes each about 35 solar masses

Black holes orbited at ~350 km separation before merging

Significant gravitational wave energy radiated

Abstract

The first direct gravitational-wave detection was made by the Advanced Laser Interferometer Gravitational Wave Observatory on September 14, 2015. The GW150914 signal was strong enough to be apparent, without using any waveform model, in the filtered detector strain data. Here, features of the signal visible in the data are analyzed using concepts from Newtonian physics and general relativity, accessible to anyone with a general physics background. The simple analysis presented here is consistent with the fully general-relativistic analyses published elsewhere,in showing that the signal was produced by the inspiral and subsequent merger of two black holes. The black holes were each of approximately 35 Msun, still orbited each other as close as ~350 km apart, and subsequently merged to form a single black hole. Similar reasoning, directly from the data, is used to roughly estimate how far these black holes were from the Earth, and the energy that they radiated in gravitational waves.