D11 Multimessenger Astronomy

Topic

Multi-messenger astronomy combines messengers of completely different natures—all originating from the same cosmic event—such as photons across the entire electromagnetic spectrum, gravitational waves, neutrinos, and cosmic rays; it combines them precisely because no single messenger can tell the full story of that event on its own.

The first-ever detected merger of two neutron stars was observed simultaneously via gravitational waves and a short gamma-ray burst, and this combined observation ushered in the era of multi-messenger astronomy.

The interferometers that detect these gravitational waves measure a relative deformation of space so minute that recording it requires arms several kilometers long and a measurement precision far smaller than the size of an atom itself.

Meanwhile, a nearby supernova was detected simultaneously in neutrinos and visible light for the first time, and this dual detection confirmed the stellar-collapse model that had produced the supernova.

A future space-based detector will extend this multi-messenger technique to much lower gravitational-wave frequencies—frequencies produced by the merger of supermassive black holes—thereby complementing the ground-based neutrino and cosmic-ray observatories that exist today. Thus, from the diverse messengers with which this text begins to the future space-based detector with which it concludes—taking in neutron star mergers, kilometer-scale interferometers, and the supernova detected in both neutrinos and light—multi-messenger astronomy allows a single cosmic event, recounted by multiple simultaneous witnesses, to reveal far more than any one of those witnesses could convey on its own.

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