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Astronomers are witnessing an unprecedented spectacle in the cosmos: a massive black hole has opened in the center of a distant galaxy.
In late 2019, a team of astronomers noticed an otherwise unremarkable galaxy named SDSS1335+0728, 300 million light-years away in the constellation Virgo. A sudden spike in the galaxy’s brightness was automatically detected by the Zwicky Transient Facility telescope at the Palomar Observatory in California.
With a very wide field of view, the camera scans the entire northern sky every two days, capturing details of celestial objects such as near-Earth asteroids as well as distant bright supernovae.
An interdisciplinary team of astronomers and engineers followed up Zwicky’s observation by using information from space and ground-based telescopes to see how the galaxy’s luminosity changed over time.
To their surprise, the researchers realized that they were witnessing a special moment when a cosmic monster woke up. The results of their study have been accepted for publication in the journal Astronomy & Astrophysics.
“Imagine you were looking at a distant galaxy for many years, and it always seemed calm and inactive,” said Paula Sánchez Sáez, lead author of the study, an astronomer at the European Southern Observatory in Germany, in a statement. “Suddenly, its (core) starts to show big changes in brightness, unlike any typical events we’ve seen before.”
The team classified the galaxy as an active galactic nucleus, or a bright, dense region powered by a supermassive black hole.
A number of celestial situations can cause a galaxy to suddenly brighten, such as supernova explosions or when stars get too close to black holes and break apart during a phenomenon called disruption events tide.
But such events last only dozens or hundreds of days—and SDSS1335+0728 continues to grow in brightness more than four years after researchers first saw it flash in luminosity like the flick of a cosmic light switch.
And the brightness variations in the galaxy are unlike anything astronomers have seen before, which made them even more alarmed.
An unprecedented cosmic event
To find answers, the team consulted archival data from NASA’s Wide Field Infrared Probe and Galaxy Evolution Explorer, the Two Micron All Sky Survey, the Sloan Digital Sky Survey and other observatories.
The researchers compared the data with follow-up observations taken by the European Southern Observatory’s Very Large Telescope, or VLT, in Chile, the Southern Astrophysical Research Telescope in Chile, the WM Keck Observatory in Hawaii and NASA’s space-based Neil Gehrels Swift and Chandra. X-ray observatories.
Together, the data sets presented a broad portrait of the galaxy before and after the December 2019 observation, revealing that the galaxy has shifted to emit significantly more ultraviolet, visible and infrared light in recent years, and X- rays starting in February – something never seen before. behavior, said Sánchez Sáez.
Since the galaxy is 300 million light-years away, the events seen by astronomers took place in the past – but the light from these events is just reaching Earth after traveling across space with the millions of years. One light year is the distance light travels in one year, which is 5.88 trillion miles (9.46 trillion kilometers).
“The most tangible option to explain this phenomenon is that we are seeing how the (core) of the galaxy is starting to show activity (…),” said co-author of the study Lorena Hernández García, an astronomer in Millennium Institute of Astrophysics and National University of Ireland. Valparaiso, both in Chile, in a statement. “If so, this would be the first time we’ve seen a supermassive black hole being activated in real time.”
Heavenly giants sleep
Supermassive black holes are classified as massive holes with a mass greater than 100,000 times that of our sun. They can be found in the center of most galaxies, including the Milky Way.
“These giant monsters are usually asleep and not directly visible,” study co-author Claudio Ricci, an associate professor at the University of Diego Portales in Chile, said in a statement. “In the case of SDSS1335+0728, we were able to observe the wake of the supermassive black hole, (which) suddenly feasted on available gas around it, becoming very bright.”
Previous research has shown inactive galaxies that appeared to become active after several years, which usually triggers black hole activity, but the process of black hole awakening has not been directly observed before, until now, Hernández said. Garcia.
The same scenario could play out with Sagittarius A*, the supermassive black hole at the center of the Milky Way, but astronomers aren’t sure how likely it is, Ricci said.
Astronomers cannot rule out that their observation could be an unusually slow episode of tidal disruption, or a new, unfamiliar phenomenon.
“Regardless of the nature of the changes, (this galaxy) provides valuable information on how black holes grow and evolve,” said Sánchez Sáez. “We expect that instruments like (MUSE on the VLT or those on the upcoming Very Large Telescope) will be key to understanding (why the galaxy is brightening).
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