PREVIEW

Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), astronomers have identified a remarkable quasar that not only stands as the brightest of its kind but also claims the title of the most luminous object ever documented.
Quasars, the luminous cores of distant galaxies, are powered by supermassive black holes, and this particular quasar showcases a black hole expanding in mass at an unprecedented rate of one Sun per day.
The energetic process by which black holes collect matter from their surroundings emits vast amounts of light, rendering quasars some of the brightest objects visible in our sky, even from great distances. As a general rule, the luminosity of quasars correlates with the rapid growth of supermassive black holes.
Christian Wolf, an astronomer at the Australian National University (ANU) and lead author of the study published in Nature Astronomy, revealed: "We have discovered the fastest-growing black hole known to date. It has a mass of 17 billion Suns, and eats just over a Sun per day. This makes it the most luminous object in the known Universe."
The quasar, named J0529-4351, is so distant that its light took over 12 billion years to reach Earth.
The matter drawn toward the black hole forms a disc that emits so much energy that J0529-4351 is over 500 trillion times more luminous than the Sun. ANU PhD student and co-author Samuel Lai emphasized the unprecedented size of the hot accretion disc, measuring seven light-years in diameter – a dimension described as the largest accretion disc in the Universe.
Surprisingly, this record-breaking quasar, J0529-4351, was hiding in plain sight for decades.
Co-author Christopher Onken noted: "It is a surprise that it has remained unknown until today when we already know about a million less impressive quasars. It has literally been staring us in the face until now."
Despite showing up in images from the ESO Schmidt Southern Sky Survey dating back to 1980, it went unrecognised as a quasar until recently.
The discovery of quasars relies on precise observational data covering large areas of the sky, often analyzed using machine-learning models. However, these models may reject new quasars if they are more luminous than those previously known, classifying them as stars. J0529-4351 initially escaped notice as a quasar in automated data analysis from the European Space Agency’s Gaia satellite, which suggested it might be a star due to its brightness.
The revelation that J0529-4351 is the most luminous quasar ever required data from the X-shooter spectrograph on ESO’s VLT, highlighting the significance of larger telescopes and more precise instruments.