Black hole in distant galaxy dazzles scientists with unprecedented flare

Astronomers worldwide witnessed an extraordinary phenomenon in the centre of a distant galaxy. It was the first event of its kind to be observed in the history of astronomy.

In 2019, a galaxy designated as SDSS1335+0728, which had not stood out in any way and was located 180 million light-years from our planet, suddenly began to brighten. This unexpected flare drew the attention of scientists, who began to intensely observe the phenomenon using various instruments, both space-based and ground-based. Among them was the Very Large Telescope (VLT), which is part of the European Southern Observatory (ESO) located in Chile.

Professor Paula Sánchez Sáez from ESO describes the phenomenon as follows: "Imagine watching a distant galaxy for years, and it always seemed calm and inactive. Suddenly, you see violent changes in its brightness, unlike anything we knew before."

The galaxy's brightening could be caused by various phenomena, such as a supernova explosion or the so-called tidal disruptions, which occur when a black hole rips apart a star approaching it. However, these flares usually last only a few tens to a maximum of a few hundred days. In the case of galaxy SDSS1335+0728, the flare has continued for over four years since the first changes were noticed.

Furthermore, the characteristics of this flare differ from anything observed so far. After a thorough analysis of data collected from various instruments, scientists noticed that following the flare, the galaxy emits much more ultraviolet, visible, and infrared light. In February of this year, it also began to emit X-rays.

"Such behavior is unprecedented," stated Prof. Sánchez Sáez.

Scientists believe that the most likely explanation is a flare in the galaxy's core, where a supermassive black hole is located, similar to the center of our galaxy, the Milky Way.

"This would be the first time we've seen a black hole activate in real-time," emphasized co-author of the discovery Lorena Hernández García.

According to scientists, the black hole at the center of the observed galaxy began rapidly consuming the surrounding gas. Supermassive black holes are located in the centres of most galaxies, including our Milky Way. Therefore, a similar phenomenon could also occur in the supermassive black hole of our galaxy (Sagittarius A*), although the probability of such an event is unknown.

Astronomers worldwide continue to observe the galaxy SDSS1335+0728, trying to understand what caused its flare. There is a chance that the changes they observe might be explained differently – for example, by a prolonged tidal disruption or some utterly unknown phenomenon. "Regardless of the nature of these changes, this galaxy provides us with valuable information about how black holes grow and evolve," Prof. Sánchez Sáez points out.

"We expect that instruments such as MUSE on the VLT or those operating on the already under-construction Extremely Large Telescope (ELT) will prove crucial in understanding why the galaxy is brightening," added the professor.