Thanks to precise measurements, astronomers have observed disturbances in the pulses of neutron stars, the characteristic shape of which indicates the existence of a gravitational wave background. A doctoral candidate from the University of Warsaw contributed to the discovery.
According to the university, four teams analysing the timing of pulsars announced the results of the last dozen or so years of observations. Analyses show the existence of signals consistent with the existence of a gravitational wave background from 10(-9th power) to 10(-7.5th power) Hz.
According to the scientists, the source of this signal may be supermassive black hole binaries in merging galaxies throughout the Universe, but there is also a possibility that these waves come from phenomena occurring in the early Universe, i.e. phase transitions, inflation or cosmic strings.
Unlike the first observation of gravitational waves by the ground-based detectors LIGO and Virgo (LVK Consortium) in 2015, detecting a signal at nanohertz frequencies requires an instrument the size of an entire galaxy. This is why observations of pulsars were used in the study.
A member of one of the research groups - Parkes Pulsar Timing Array (PPTA) - is Małgorzata Curyło, a doctoral candidate at the Astronomical Observatory of the University of Warsaw.
She said: ‘Pulsars are stars that emit pulses of radio emission towards Earth with the accuracy of atomic clocks. Thanks to extremely precise measurements, astronomers were able to observe disturbances in these pulses, the characteristic shape of which indicates the existence of gravitational wave background. However, it will take many years to confirm the source of the signal.’
Gravitational-wave astronomy opens a new phase of research at many frequencies - from the 10(-9th power) Hz band, observed with pulsar timing, to the 100-1000 Hz band, observed with LVK ground-based interferometers.
Professor Tomasz Bulik from the Astronomical Observatory of the University of Warsaw said: 'The detection of gravitational waves at low frequencies opens a new window of research in astronomy, a revolution similar to the one that occurred with the beginning of the observation of the Universe - not only in the visible light range, but also in other ranges, such as radio waves. This discovery opens the field of research for decades to come.’
The analyses were performed by the PPTA, the European Pulsar Timing Array (EPTA), the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) and the Indian Pulsar Timing Array (InPTA).
The source paper was published in The Astrophysical Journal Letters. (PAP)
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