A record of brilliance and gluttony

Brightness comparable to 500 trillion suns: Astronomers have reported the brightest known object in the universe right now. It is a quasar – an active galactic nucleus. Calculations showed that the force of the radiation is due to a luminous disc of matter, which in turn is driven by a record-hungry “dark creature”: the supermassive black hole at the heart of the galaxy devours about one solar mass per day.

The short-shaped quasar stands for “quasar-stellar object” – this name indicates that these objects can appear to an observer like bright stars. But they are actually giant structures far away from us: quasars are the radiant cores of galaxies that are among the brightest objects in the universe. Its brightness is due to the influence of the supermassive black hole at the center of the galaxy. It attracts matter from the environment, which forms a rotating disk, and is then sucked in pieces by the gravitational giant. Because of the energy released in the form of radiation, the accretion disk shines so intensely that light reaches us despite sometimes enormous distances.

Beacons of the universe on the horizon

Many quasars are already known and characterized. The following applies: As a general rule, brighter black holes indicate faster-growing supermassive black holes. When it comes down to it, the international team of astronomers now offers superlatives. The object, named J0529-4351, has been known for a long time, but was thought to be a star. “It seems surprising that this quasar has remained unidentified until now, while we know of so many less impressive specimens,” says co-author Christopher Onken of the Australian National University (ANU) in Canberra. As he and his colleagues explain, this is because of the strong brightness of J0529-4351. An automatic analysis of data from the European Space Agency's Gaia satellite classified the object as too bright to be considered a quasar and identified it as a star instead.

But then, through observations made by the Australian National University's 2.3-meter telescope at Siding Spring Observatory in Australia, researchers were able to prove that J0529-4351 could not be a star: the characteristic redshift of the light showed that the object was very far away. . It is – hence it is a quasar. To reveal more details, astronomers targeted J0529-4351 with additional telescopes and analysis instruments. The X-Shooter spectrograph on the European Southern Observatory's (ESO) Very Large Telescope (VLT) provided the important data. Scientists then applied the information in models that enabled conclusions to be drawn about the properties of the quasar or black hole responsible.

Superlatives appear

This showed that quasar J0529-4351 is more than twelve billion light-years away from Earth. It still appears prominent because it shines 500 trillion times brighter than the Sun. This makes J0529-4351 not only the brightest object of its kind, but also the brightest object ever observed, astronomers say. A few years ago, there were reports of a quasar that appeared to shine with the force of 600 trillion suns. But it later turned out that the brightness was amplified by gravitational lensing – a galaxy located between us and the distant quasar. The actual brightness of J043947.08+163415.7 was then reduced to about eleven trillion solar luminosities. However, in the case of quasar J0529-4351, there are no signs of a lensing effect, the authors write.

What could be responsible for the massive luminosity can be inferred from the modeling results, as the astronomers say: “All of this light is coming from a hot accretion disk about seven light-years in diameter – this could be the largest accretion disk in the universe.” says co-author Samuel Lai of the Australian National University. It's about a black hole to which scientists can also assign amazing features: “We have discovered the fastest-growing black hole known to date. It has a mass of 17 billion solar masses and consumes just over one solar mass per day.

The research team now wants to continue observing quasar J0529-4351, or the rapidly growing black hole. The discovery and study of distant, supermassive black holes could shed light on some of the mysteries of the early universe. According to the authors, J0529-4351 now represents an ideal target for the GRAVITY+ upgrade on the European Southern Observatory's VLT Interferometer (VLTI), which aims to record the mass of black holes more precisely. The team also has high hopes for the European Southern Observatory's Extremely Large Telescope (ELT), which is currently being built in Chile's Atacama Desert.

Source: European Southern Observatory Specialized article: Natural Astronomy, doi: 10.1038/s41550-024-02195-x

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