Free Astronomy Magazine January-February 2023

46 JANUARY-FEBRUARY 2023 ASTRO PUBLISHING of short-lived, often extreme, events that could then be studied in much greater detail by telescopes such as ESO’s VLT in Chile. “We developed an open-source data pipeline to store and mine important informa- tion from the ZTF survey and alert us about atypical events in real time,” explains Igor Andreoni, an as- tronomer at the University of Mary- land in the US who co-led the paper published today in Nature together with Michael Coughlin from the Uni- versity of Minnesota. In February of this year the ZTF de- tected a new source of visible light. The event, named AT2022cmc, was reminiscent of a gamma ray burst — the most powerful source of light in the Universe. The prospect of witnessing this rare phenomenon prompted astronomers to trigger several telescopes from across the globe to observe the mystery source in more detail. This included ESO’s VLT, which quickly observed this new event with the X-shooter instru- ment. The VLT data placed the source at an unprecedented dis- tance for these events: the light pro- duced from AT2022cmc began its journey when the universe was about one third of its current age. A wide variety of light, from high en- ergy gamma rays to radio waves, was collected by 21 telescopes around the world. The team com- pared these data with different kinds of known events, from collaps- ing stars to kilonovae. But the only scenario that matched the data was a rare jetted-TDE pointing towards by ESO - Juan Carlos Muñoz Mateos Most distant detection of a black hole swallowing a star S tars that wander too close to a black hole are ripped apart by the incredible tidal forces of the black hole in what is known as a tidal disruption event (TDE). Approx- imately 1% of these cause jets of plasma and radiation to be ejected from the poles of the rotating black hole. In 1971, the black hole pioneer John Wheeler introduced the con- cept of jetted-TDEs as “a tube of toothpaste gripped tight about its middle,” causing the system to “squirt matter out of both ends.” “We have only seen a handful of these jetted-TDEs and they remain very exotic and poorly understood events,” says Nial Tanvir from the University of Leicester in the UK, who led the observations to deter- mine the object’s distance with the VLT. Astronomers are thus constantly hunting for these extreme events to understand how the jets are actually created and why such a small frac- tion of TDEs produce them. As part of this quest many tele- scopes, including the Zwicky Tran- sient Facility (ZTF) in the US, repeatedly survey the sky for signs T his artist’s impression illustrates how it might look when a star approaches too close to a black hole, where the star is squeezed by the intense gravita- tional pull of the black hole. Some of the star’s material gets pulled in and swirls around the black hole forming the disc that can be seen in this image. In rare cases, such as this one, jets of matter and radiation are shot out from the poles of the black hole. In the case of the AT2022cmc event, evidence of the jets was detected by various telescopes including the VLT, which determined this was the most distant example of such an event. [ESO/M.Kornmesser]