Kilonova

A brief astronomical transient powered by radioactive decay in neutron-rich debris from a compact-object merger. Its ejecta forge heavy elements, including gold and platinum.

Neutron star merger: A collision and coalescence of two neutron stars, releasing gravitational waves and ejecting matter. The merger launches the neutron-rich material whose radioactive decay powers a kilonova.
GW170817: A gravitational-wave signal detected in 2017 from the merger of two neutron stars. Its counterpart established the first directly observed kilonova associated with a neutron-star merger.
Nucleosynthesis: The formation of atomic nuclei through nuclear reactions in cosmic environments. Kilonova spectra test whether compact-object mergers contribute substantially to heavy-element nucleosynthesis.
Supernova: A stellar explosion that produces a dramatic increase in brightness and ejects stellar material. Supernovae usually arise from stellar death, whereas kilonovae follow compact-object mergers.
R-process: A sequence of rapid neutron captures that builds many elements heavier than iron. Kilonova ejecta provide conditions for this process to synthesize heavy nuclei.
AT2017gfo: The optical and infrared transient associated with the neutron-star merger GW170817. Its fading colors and spectra became the benchmark observations for kilonovae.
Gravitational-wave astronomy: The study of astronomical objects and events through gravitational-wave measurements. Joint wave and light observations of kilonovae reveal merger properties unavailable from either channel alone.
Macronova: An alternative name historically used for the optical and infrared transient from a compact-object merger. The competing label reflects early uncertainty about how merger-powered transients should be named.
Radioactive decay: The spontaneous transformation of unstable atomic nuclei, often releasing particles or photons. Decay of freshly made nuclei deposits the heat that keeps the ejecta luminous.
LIGO: A pair of observatories that detect gravitational waves using laser interferometry. LIGO detected the merger whose electromagnetic counterpart revealed a kilonova.

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