Gravitational Waves: Detection Methods and Recent Discoveries — A Review of Interferometric Astronomy from LIGO-Virgo-KAGRA to the Next-Generation Era

Abstract

ABSTRACT Gravitational-wave astronomy has matured, within less than a decade, from a landmark first detection into a routinely productive observational discipline. This paper undertakes an analytical review of the detection methods underlying this transformation and the scientific discoveries they have enabled, from the first direct observation of gravitational waves in September 2015 through the completion of the fourth Advanced LIGO-Virgo-KAGRA observing run in November 2025. Drawing on secondary data compiled from the Gravitational Wave Transient Catalogs published by the LIGO-Virgo-KAGRA Collaboration, public detector data releases, and peer-reviewed literature, the study examines the evolution of laser interferometric detection technology, cumulative detection trends across four observing runs, and landmark discoveries including the first binary neutron star merger observed with an electromagnetic counterpart and recent high-significance events from the current observing era. The analysis indicates that cumulative confirmed detections grew from 11 events at the end of the second observing run to over 250 candidate events by the conclusion of the fourth observing run, driven substantially by improvements in detector strain sensitivity and the expansion of the global detector network. The paper identifies a persistent research gap concerning the limited electromagnetic characterization of compact objects in the so-called mass gap between neutron stars and black holes, and the continued absence of a fully operational Southern Hemisphere or South Asian detector capable of closing existing gaps in all-sky localization coverage. Based on the findings, the study proposes an integrated conceptual framework linking compact binary inspiral, interferometric strain detection, multi-detector triangulation, and astrophysical and cosmological insight, and discusses its implications for the planned next-generation detector era.

KEYWORDS: Gravitational Waves, LIGO, Virgo, KAGRA, Interferometric Detection, Binary Black Hole Mergers, Multi-Messenger Astronomy, Gravitational-Wave Astronomy