New research from the University of Birmingham reveals that collisions between massive black holes should be observable by both gravitational wave and X-ray observatories by the start of the next decade.
For the first time, scientists have directly detected gravitational waves — ripples in space-time — in addition to light from the spectacular collision of two neutron stars. This marks the first time that a cosmic event has been viewed in both gravitational waves and light.
The discovery was made using the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO), the Europe-based Virgo detector, and some 70 ground- and space-based observatories. This co-observation represents the fulfilment of the promise of ‘multi-messenger’ astronomy opened up by the first measurement of gravitational waves by LIGO/VIRGO in 2015.
The study, published in Nature Astronomy, points to the coordination of two of the European Space Agency’s (ESA) major space observatories of the 2030s — Athena, the next-generation X-ray space telescope and LISA, the first space-based gravitational wave observatory.
The two projects will be timed to launch so they can be coordinated to begin observations within a year of each other. This will kick-start a period of at least four-years of synchronized science operations and the promise of delivering data on events that no-single technique in astronomy could collect.
This should give astronomers an unprecedented opportunity to create ‘multi-messenger maps’ of the universe with objects and events seen in both the electromagnetic and gravitational wave spectrums. As such, this will enable us to ‘see’ violent events in the Universe that have previously been invisible. Events that could hold the key to unlocking long-standing mysteries in our understanding of cosmic evolution.
These events include collisions between supermassive black holes in distant galaxies and massive black holes consuming compact stellar remnants such as neutron stars and even more diminutive black holes.
The gravitational waves measured by LISA will pinpoint the ripples of space-time that the mergers cause while the X-rays observed with Athena reveal the hot and highly energetic physical processes in that environment. Combining these two messengers to observe the same phenomenon in these systems would bring a huge leap in our understanding of how massive black holes and galaxies co-evolve, how massive black holes grow their mass and accrete, and the role of gas around these black holes.
Professor Alberto Vecchio, Director of the Institute for Gravitational Wave Astronomy, University of Birmingham, and a co-author of the study, has worked on the LISA project for twenty years. He sees the double-punch of LISA/Athena as a fulfilment of his and his colleagues’ hard work: “The prospect of combining forces with the most powerful X-ray eyes ever designed to look right at the centre of galaxies promises to make this long haul even more rewarding.”