Scientists just witnessed a huge black hole 'waking up' and shining brightly all of a sudden

Black holes are the most fascinating yet mysterious astronomical objects ever studied. Dubbed “cosmic monsters,” these concentrated masses of energy are known to devour everything that touches their boundary. Unless any cosmic object such as a star or a planet comes near a black hole, it remains dormant. But each time a star collapses and pricks its boundary line, the black hole gets triggered into awakening. Recently, a team of researchers reported that they have witnessed the roaring awakening of a massive black hole that is 1 million times the mass of the Sun, per The Guardian. The detailed study will be published in Astronomy & Astrophysics.

The black hole that has been waking up from a long-time slumber, sits at the center of a galaxy codenamed SDSS1335+0728. The galaxy floats in the Virgo constellation, 300 million light years away from Earth. Scientists had been observing this galaxy for years but nothing noteworthy was observed. This changed in December 2019 when they started noticing that the galaxy was emitting an unusual flare, a dramatic surge in luminosity unlike they had ever witnessed before. The brightness kept on increasing, and after four years, it was still glaring bright. Upon analyzing data from various standpoints, they concluded that the giant supermassive beast was waking up.

“These giant monsters usually are sleeping and not directly visible,” said study co-author Claudio Ricci, associate professor at Diego Portales University in Chile, in a press release by ESO (European Southern Observatory). “In the case of SDSS1335+0728, we were able to observe the awakening of the massive black hole, which suddenly started to feast on gas available in its surroundings, becoming very bright.”

Scientists first came to know about the glaring galaxy through Zwicky Transient Facility in California where they recorded a sudden leap in the galaxy's brightness in 2019. Further observations indicated that the galaxy had become four times brighter. It was emitting not only ultraviolet and infrared frequencies but was also spewing 10 times more X-rays than before. Four years later, it is still getting brighter each day. “We discovered this source at the moment it started to show these variations in luminosity,” said Dr Paula Sánchez-Sáez, an astronomer at ESO headquarters in Germany told The Guardian. “It’s the first time we’ve seen this in real-time.”

The only reason they could propose, behind this bright light, was that the black hole encountered huge amounts of material in its periphery, either through the crushing of a massive star or through a supernova explosion. “This behavior is unprecedented,” Dr. Paula added in the ESO press release, “Imagine you’ve been observing a distant galaxy for years, and it always seemed calm and inactive. Suddenly, its core starts showing dramatic changes in brightness, unlike any typical events we've seen before.” Study co-author Lorena Hernández García of the Millennium Institute of Astrophysics in Chile, also said in the press release that a flare like this "has never been observed before" in real-time.

The researchers hypothesized that the most likely explanation is the creation of an “active galactic nucleus” where a vast black hole at the center of the galaxy starts actively consuming the material around it. As the black hole eats up the surrounding objects, the active galactic nucleus emits a broad spectrum of light, heating up, glowing, and radiating light.

Apart from this, the team also considered the possibility of a “tidal disruption event (TDE).” TDE refers to the process when a star is ripped apart, crushed, and pulled inside a black hole for coming too close to its boundary. The black hole strips away the glowing, superheated material from planets, stars, gas, dust, and other black holes, and gobbles it in. Once this material is lost forever inside the black hole, it emits unusually bright rings of light at its boundary.

However, the possibility of TDE was ruled out later because TDE usually lasts for a brief period like a few hundred days. But this galaxy has been glowing for more than four years. “The most tangible option to explain this phenomenon is that we are seeing how the core of the galaxy is beginning to show activity,” said García. “If so, this would be the first time that we see the activation of a massive black hole in real-time,” she added. 

To further analyze the phenomenon, the team consulted archival data from NASA’s Wide-field Infrared Survey Explorer and Galaxy Evolution Explorer, the Two Micron All Sky Survey, the Sloan Digital Sky Survey, and other observatories, per CNN. They compared the data with follow-up observations taken by the ESO’s Very Large Telescope (VLT), the Southern Astrophysical Research Telescope in Chile, the W. M. Keck Observatory in Hawaii, and NASA’s space-based Neil Gehrels Swift and Chandra X-ray observatories.

They believe that if they can decipher the mystery behind this black hole awakening, they will be able to reveal some interesting insights about how black holes evolve. “Regardless of the nature of the variations, (this galaxy) provides valuable information on how black holes grow and evolve,” Dr. Paula said. “We expect that instruments like MUSE on the VLT or those on the upcoming Extremely Large Telescope will be key in understanding why the galaxy is brightening.”