The brightest object in the universe is a quasar with a black hole inside

The light from the brightest object known took more than 12 billion years to reach Earth, since the infancy of the universe. The light from this quasar, as this type of object is known, was so intense that for a time it was thought to be a nearby star. It appeared in sky surveys 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, which formed around a black hole with the mass of more than 17 billion suns. This object devours matter equivalent to our Sun every day and affects its surroundings in such a way that it emits enormous amounts of light — light that has 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, published an analysis in the journal Nature Astronomy showing that the J0529-4351 quasar is the fastest growing and brightest of all known quasars.

Quasars, or quasi stellar objects, are so called because, when they began to be discovered with radio telescopes in the late 1950s, astronomers realized that these distant and powerful objects had been mistaken for simple nearby stars when seen through telescopes. Since then, more than a million have been identified. But they are often hidden from the naked eye, as the authors of the paper explain. In an automated analysis of data obtained by Gaia, a European Space Agency probe that has cataloged some one 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 object’s distances, dimensions and brightness with the X-shooter spectrograph on the Very Large Telescope (VLT), the European Southern Observatory’s facility in Chile’s Atacama Desert.

Mar Mezcua, from the Institute of Space Sciences (ICE-CSIC), in Barcelona, argues 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 process it properly, there are many discoveries that go unnoticed.” In the search for quasars, large regions of the sky are analyzed and then models, including machine learning tools, 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. This makes it difficult to make new discoveries when objects deviate from the norm.

For Isabel Márquez, from the Institute of Astrophysics of Andalusia in Spain, the size of this object will be useful when it comes to testing the relationship between the mass and luminosity of distant black holes, which currently requires many extrapolations. “When the ELT [the Extremely Large Telescope, which is being built in Chile] is working 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 assess whether the estimates that used to calculate the sizes and other characteristics of black holes are adequate. On the VLT, there is an instrument called GRAVITY+ that is used to measure the mass of black holes. The quasar J0529-4351 will help update it.

The discovery of such large objects in early stages of the universe shows “the predilection of the universe to form 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,” she adds.

In Mezcua’s opinion, this kind of discovery “gives weight to the black hole seed theory.” It’s a type of object that could help explain how such massive black holes could have formed so early on in the universe, when it is not clear how so much matter could have been formed. Discoveries like J0529-4351 or those being made by the James Webb Space Telescope, which is detecting black holes even older than J0529-4351, which appeared just 400 million years after the Big Bang, are rewriting the history of the early days of the cosmos — an investigation that is essential to understanding how the cosmos evolved into the universe that we live in today.

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