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	Pulsar Timing Array	Epoca della Reionizzazione 21-cm
Campo	Astronomia	Astronomia
Famiglia	Process / pipeline	Process / pipeline
Anno di origine	1979	1990
Ideatore	Stephen Detweiler	David Scott
Tipo	Observational timing method	Radio observational method
Fonte seminale	Sazhin, M. V. (1978). Opportunities for detecting ultralong gravitational waves. Soviet Astronomy, 22, 36-38.	Scott, D., & Rees, M. J. (1990). The 21-cm signature of the ionization of the intergalactic medium. Monthly Notices of the Royal Astronomical Society, 247, 510-516.
Alias	PTA, Millisecond Pulsar Timing, Pulsar Timing Residuals	EoR 21-cm, Hydrogen Line Observations, 21-cm Signal Mapping
Correlati	3	3
Sintesi	A pulsar timing array uses multiple millisecond pulsars as a distributed network of gravitational wave detectors across the galaxy. Proposed theoretically by Stephen Detweiler in 1979, this method exploits the extraordinary timing precision of pulsars to detect the subtle spacetime distortions caused by gravitational waves. In 2023, the first evidence for a stochastic background of gravitational waves was announced using pulsar timing arrays.	The 21-centimeter line observation of neutral hydrogen is a powerful technique for studying the Epoch of Reionization, when the first stars and galaxies ionized the intergalactic medium about 13 billion years ago. Proposed by Scott and Rees in 1990, this method probes the universe's transition from the dark ages to the cosmic dawn through the characteristic hyperfine line emission of hydrogen.