An article published in the journal “Monthly Notices of the Royal Astronomical Society” reports a study on a tidal disruption event cataloged as AT2019qiz in which it was possible to see the phases in which a star was destroyed by a supermassive black hole. A team of researchers led by astrophysicist Matt Nicholl from the British University of Birmingham used various telescopes including ESO’s Very Large Telescope (VLT) and New Technology Telescope (NTT) and NASA’s Spitzer space observatory to follow this event, which lasted about six months, with the star’s “spaghettification” and about half of it swallowed by the black hole.
The AT2019qiz event occurred in the galaxy 2MASX J04463790-1013349, also known as WISEA J044637.88-101334.9, about 215 million light-years from Earth. On September 19, 2019, warnings began circulating that several observers had detected emissions in various electromagnetic bands typical of tidal disruption events. That’s the consequence of a star passing too close to a supermassive black hole whose gravity destroys the star. That type of event has already been spotted and reported for example in an article published in “The Astrophysical Journal” in September 2019 and cataloged as ASASSN-19bt. In the case of the AT2019qiz event, its detection with various instruments from the beginning allowed it to be followed for the six months of its duration with excellent coverage.
Sergio Campana of the Italian National Institute of Astrophysics in Milan, one of the authors of this study, explained that he and his colleagues analyzed the data detected by the Swift space observatory and found that the X-ray emissions arrived almost at the same time as the ones in visible light. This indicates that spaghettification of the star leads to the rapid accretion of matter on the supermassive black hole at the center of the galaxy that hosts it. The researcher stressed the importance of observations at different wavelengths, which provide complementary information on the same phenomenon, as if we could look at the star’s disruption simultaneously with many different eyes.
Francesca Onori of the Italian National Institute of Astrophysics of Teramo, one of the authors of this study, explained that she and her colleagues were able to follow practically the entire evolution of the phenomenon through the evolution of the optical spectra over time. The researcher also stressed the importance of such an accurate observation campaign to obtain information on the characteristics of the stellar material in accretion on a supermassive black hole. She mentioned observing the dissolving blanket of obscuring debris and the high velocities of the stellar material itself as an example.
Regarding the star that was destroyed, Matt Nicholl explained that the observations indicate that it had roughly the mass of the Sun, and about half of it was swallowed by the supermassive black hole, which has a mass over a million times greater.
The galaxy where the AT2019qiz event took place is close enough to have allowed the collection of a lot of data and consequently a detailed study. It will help understand the behaviors of extreme objects such as supermassive black holes and the behavior of matter in surrounding environments, where gravity is extreme.