Free Astronomy Magazine May-June 2024

MAY-JUNE 2024 pher Onken, an astronomer at ANU. He added that this object showed up in images from the ESO Schmidt Southern Sky Survey dating back to 1980, but it was not recognised as a quasar until decades later. Finding quasars requires precise ob- servational data from large areas of the sky. The resulting datasets are so large, researchers often use ma- chine-learning models to analyse them and tell quasars apart from other celestial objects. However, these models are trained on existing data, which limits the potential can- didates to objects similar to those already known. If a new quasar is more luminous than any other pre- viously observed, the programme might reject it and classify it instead as a star not too distant from Earth. An automated analysis of data from the European Space Agency’s Gaia satellite passed over J0529-4351 for being too bright to be a quasar, sug- gesting it to be a star instead. The researchers identified it as a distant quasar last year using observations from the ANU 2.3-metre telescope at the Siding Spring Observatory in Australia. Discovering that it was the most luminous quasar ever ob- served, however, required a larger telescope and measurements from a more precise instrument. The X- shooter spectrograph on ESO’s VLT in the Chilean Atacama Desert pro- vided the crucial data. The fastest-growing black hole ever observed will also be a perfect tar- get for the GRAVITY+ upgrade on ESO’s VLT Interferometer (VLTI), which is designed to accurately measure the mass of black holes, in- cluding those far away from Earth. Additionally, ESO’s Extremely Large Telescope (ELT), a 39-metre tele- scope under construction in the Chilean Atacama Desert, will make identifying and characterising such elusive objects even more feasible. Finding and studying distant super- T his image shows the region of the sky in which the record- breaking quasar J0529-4351 is situ- ated. Using ESO’s Very Large Tele- scope (VLT) in Chile, this quasar has been found to be the most lumi- nous object known in the Universe to date. This picture was created from images forming part of the Digitized Sky Survey 2, while the inset shows the location of the quasar in an image from the Dark Energy Survey. [ESO/Digitized Sky Survey 2/Dark Energy Survey] stronomers have characterised the most luminous quasar ob- served to date, which is powered by the fastest-growing black hole. This black hole is growing in mass by the equivalent of one Sun per day. The matter being pulled in toward this black hole forms a disc that meas- ures seven light-years in diameter — about 15,000 times the distance from the Sun to the orbit of Neptune. [ESO] massive black holes could shed light on some of the mysteries of the early Universe, including how they and their host galaxies formed and evolved. But that’s not the only rea- son why Wolf searches for them. “Personally, I simply like the chase,” he says. “For a few minutes a day, I get to feel like a child again, playing treasure hunt, and now I bring everything to the table that I have learned since.” !