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 , 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.

Highlights

  • Advanced LIGO made the first observation of a gravitational wave (GW) signal, GW150914 [1], on September 14th, 2015, a successful confirmation of a prediction by Einstein’s theory of general relativity (GR)

  • A lot of insight can be obtained by applying these basic physics arguments to the observed strain data of GW150914

  • These show the system that produced the gravitational wave was a pair of inspiraling black holes that approached very closely before merging

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Summary

Introduction

Advanced LIGO made the first observation of a gravitational wave (GW) signal, GW150914 [1], on September 14th, 2015, a successful confirmation of a prediction by Einstein’s theory of general relativity (GR). The result that GW150914 was emitted by the inspiral and merger of two black holes follows from (1) the strain data visible at the instrument output, (2) dimensional and scaling arguments, (3) primarily Newtonian orbital dynamics and (4) the Einstein quadrupole formula for the luminosity of a gravitational wave source.. The result that GW150914 was emitted by the inspiral and merger of two black holes follows from (1) the strain data visible at the instrument output, (2) dimensional and scaling arguments, (3) primarily Newtonian orbital dynamics and (4) the Einstein quadrupole formula for the luminosity of a gravitational wave source.1 These calculations are straightforward enough that they can be readily verified with pencil and paper in a short time.

Analyzing the observed data
Evidence for compactness in the simplest case
The case of unequal masses
Orbital eccentricity
The effect of objects’ spins
Newtonian dynamics and compactness
Possible redshift of the masses – a constraint from the luminosity
Luminosity and distance
Conclusions
Gravitational radiation from a different rotating system
Findings
Mode analysis
Full Text
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