The light from the most luminous object known took more than 12 billion years to reach Earth, since the infancy of the universe. The light from this quasar, as these types of objects are known, was so intense that, for a time, it was thought to be a nearby star. It appeared in sky scans from 1980 and then in a recent one from 2022, but in both cases J0529-4351, as the object has been named, was thought to be a sun. However, it was a quasar, a gigantic disk of gas and dust, seven light years in diameter, formed around a hole with the mass of more than 17 billion suns. This object devours the matter equivalent to our Sun every day and shakes its surroundings in such a way that it emits enormous amounts of light that have reached us since the dawn of the cosmos. This week, a team of scientists led by Christian Wolf, from the Australian National University in Canberra, publishes in the journal Nature Astronomy an analysis that shows that quasar J0529-4351 is the fastest growing of all known and the brightest.
Quasars, from English quasi stellar object (near-stellar objects), they are so called because, when they began to be discovered with radio telescopes at the end of the 1950s, astronomers realized that those distant and powerful objects had been confused when seen by the telescope with simple nearby stars. Since then, more than a million have been identified. But they are often hidden in plain sight, as the authors of the article say. In an automated analysis of the data obtained by Gaia, a European Space Agency probe that has cataloged some billion astronomical objects, J0529-4351 was thought to be too bright to be a quasar and was identified as a star. Its true nature was revealed last year with observations from the Australian National University’s 2.3-meter telescope at the Siding Spring Observatory. Scientists were then able to accurately estimate the distances, dimensions and brightness of the object with the spectrograph. X-shooter of the Very Large Telescope (VLT), the facility of the European Southern Observatory in the Atacama Desert, Chile.
Mar Mezcua, from the Institute of Space Sciences (ICE-CSIC), in Barcelona, considers that the most interesting aspect of the work is that it shows how “although we have an immense amount of data, if we are not able to treat it well, there are many discoveries that go unnoticed.” In the search for quasars, large regions of the sky are analyzed and then models, sometimes machine learning, are used to try to distinguish quasars from stars or other celestial objects. As with other similar computer models, they are trained with images of what is known and classified, something that makes it difficult to make new discoveries when objects deviate from the norm.
For Isabel Márquez, from the Institute of Astrophysics of Andalusia, CSIC, the size of this object will be useful to test the relationships between mass and luminosity of distant black holes, something that, until now, requires many extrapolations. “When the ELT (the Extremely Large Telescope, which is being built in Chile) works and optical interferometry can be done, it will be one of the first objects that will be investigated,” says Márquez. This very bright quasar will help us find out if the estimates used to calculate the sizes and other characteristics of black holes are adequate. On the VLT there is an instrument, GRAVITY+, that is used to measure the mass of black holes and the quasar J0529-4351 will serve to update it.
The discovery of such large objects in early stages of the universe shows “the universe’s predilection for forming very massive objects, in denser areas and with more galaxies than now,” explains Márquez. “In the later universe these objects can no longer be generated,” he adds. In Mezcua’s opinion, this type of discovery “gives weight to the theory of seed holes”: a type of objects that would help explain how such massive black holes formed so early, when it is not clear how so much matter could have accumulated. Discoveries like the one announced today or those being made by the space telescope James Webbwhich is detecting black holes even older than J0529-4351, which appeared only 400 million years after the Big Bang, are reconstructing the history of those early days of the cosmos, essential to understanding how it evolved into the universe we inhabit.
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