The mysterious brightening of a galaxy far, far away has been traced to the heart of the galaxy and the sudden awakening of a giant black hole 1m times more massive than the sun.
Decades of observations have found nothing remarkable about the distant galaxy in the constellation Virgo, but that changed in late 2019 when astronomers noticed a dramatic increase in its brightness that continues to this day.
Researchers now believe they are witnessing changes never seen before, with the black hole at the galaxy’s core putting on an extreme cosmic light show as huge amounts of material fall into it.
“We discovered this source at the moment it started to show these variations in brightness,” said Dr Paula Sánchez-Sáez, a staff astronomer at the European Southern Observatory headquarters in Garching, Germany. “This is the first time we’ve seen it in real time.”
The galaxy, which goes by the snappy codename SDSS1335+0728 and lies 300m light-years away, was flagged to astronomers in December 2019 when an observatory in California called the Zwicky Transient Facility recorded a sudden increase in its brightness.
The warning prompted a flurry of new observations and checking of archived measurements from ground- and space-based telescopes to understand more about the galaxy and its past behavior.
The scientists discovered that the galaxy recently doubled in brightness in mid-infrared wavelengths, became four times brighter in the ultraviolet, and at least 10 times brighter in the X-ray range.
What caused the sudden brightening is unclear, but sign up Astronomy and Astrophysicsthe researchers say the most likely explanation is the creation of an “active galactic nucleus” where a large black hole at the center of a galaxy begins to actively consume the material around it.
Active galactic nuclei emit a broad spectrum of light as gas around the black hole heats and glows, and surrounding dust particles absorb some wavelengths and re-emit others.
But this is not the only possibility. The team did not rule out an exotic form of “tidal disruption event,” a highly restricted phrase to describe a star that is torn apart after straying too close to a black hole.
Tidal disruption events tend to be short-lived affairs, brightening a galaxy for no more than a few hundred days, but more measurements are needed to rule out the process. “With the data we currently have, it is impossible to disentangle which of these scenarios are real,” Sánchez-Sáez said. “We must continue to monitor the source.”
