Determine how surprising gravitational-wave astronomy will be

Determine whether gravitational-wave astronomy will ultimately prove as surprising as its electromagnetic-astronomy predecessors, including whether future gravitational-wave observations will reveal unexpected phenomena or fundamentally new astrophysical and physical insights.

Background

The review discusses how gravitational-wave astronomy has already produced unexpected findings, including unexpectedly massive stellar black holes, compact objects in the lower mass gap, and the multimessenger phenomena associated with GW170817. Future ground-based, space-based, and deci-hertz detectors will expand both the sensitivity and frequency range of observations, potentially exposing new populations, unexplored cosmic epochs, subtle deviations from general-relativistic waveforms, or entirely new source classes.

The authors explicitly leave unresolved whether these expanded observations will generate surprises comparable to those produced by new electromagnetic observing bands, such as pulsars, quasars, cosmic acceleration, and fast radio bursts. The uncertainty concerns the ultimate scientific character and scale of discoveries enabled by gravitational-wave astronomy, rather than a specific source population or observational measurement.

References

Whether GW astronomy will prove as surprising as its EM predecessors is, however, an open question.

— The Promise of Gravitational-Wave Astronomy  (2610.17647 - Ajith, 13 Oct 2026) in Section “Concluding remarks: The element of surprise in GW astronomy”