Almost every galaxy has a black hole: a massive black hole that's millions or even billions of times heavier than our Sun. Some of these black holes lie dormant and dark for thousands of years, unnoticeable to astronomers' eyes, whereas others shine bright.
The dormant ones become visible when a star passes too close to it, and the passing star ends up being shredded to pieces and swallowed up — this phenomenon creates a tidal disruption event (TDE), which shines as brightly as a supernova.
Thanks to updated technology, astronomers are now able to capture these TDEs, opening up insights into these events and the hidden black holes.
Trying to understand black holes
"We’re still in the trenches, trying to understand the physical mechanisms powering these emissions," said Suvi Gezari of the University of Maryland, College Park.
Gezari presented an analysis of 39 TDEs earlier this month, with 22 recently captured TDEs, and 17 older ones. The first TDE was spotted by an x-ray mapping satellites back in the 1990s.
In a regular TDE image, a black hole's gravity shreds an approaching star into thin strips. The black hole then swallows half of the star's matter while the rest of it moves away in long streams.
Now, survey telescopes like California's Zwicky Transient Facility (ZTF) also capture these events and alert other observatories like NASA's Swift telescope. These then make follow-up observations with ultraviolet and x-ray wavelengths.
However, even with these technologies, astronomers are still looking to find out how to calculate a black hole's mass. So far, crude measurements are created thanks to the black hole's galaxy size.
Luckily, more and more TDEs are being captured, with hundreds of thousands of new discoveries expected to happen every year. As Gezari mentioned "My dream is for TDEs to be some kind of ruler or scale for black hole mass. We’re not there yet but we’re getting closer."