When most of us get the urge to watch some violence and explosions on a grand scale, we head to the nearest cinema for the latest action thriller. When astronomers get that urge, they head to the nearest space telescope and look for the latest tidal disruption event (TDE). This don’t happen nearly as often as Vin Diesel flicks, but astronomers assure us that watching black holes consume stars that dare to violate their space is much more satisfying. This only happens about once every 10,000 to 100,000 years in a galaxy the size of the Milky Way and they’ve managed to see about 40 of them. However, they’ve never seen one like ASASSN-19bt, which they recently watched shred a star into solar spaghetti strands before twirling it on a cosmic fork and slurping it down. (Note to self – never write while hungry.)
Before we go any further, let’s address the obvious — ASASSN-19bt would be a great name for a killer movie robot, the Tidal Disruptions would make a great name for a band and the Tidal Disruption Event would be a super name for a monster truck rally on a beach.
Back to ASASSN-19bt. Its discovery was an accident by astronomers from Carnegie Observatories using NASA’s Transiting Exoplanet Survey Satellite (TESS) and a worldwide network of robotic telescopes headquartered at The Ohio State University called ASAS-SN (All-Sky Automated Survey for Supernovae).
“We’ve been closely monitoring the regions of the sky where TESS is observing with our ASAS-SN telescopes, but we were very lucky with this event in that the patch of the sky where TESS is continuously observing is small, and in that this happened to be one of the brightest TDEs we’ve seen. Due to the quick ASAS-SN discovery and the incredible TESS data, we were able to see this TDE much earlier than we’ve seen others — it gives us some new insight into how TDEs form.”
Patrick Vallely, National Science Foundation Graduate Research Fellow at Ohio State and co-author of the paper on the discovery published this week in The Astrophysical Journal, described the lucky discovery in an OSU press release. Chris Kochanek, a professor of astronomy at OSU, explains the odds of finding a TDE, which can only occur if the black hole is extremely close to a star — about the distance from Earth to the Sun.
“Imagine that you are standing on top of a skyscraper downtown, and you drop a marble off the top, and you are trying to get it to go down a hole in a manhole cover. It’s harder than that.”
The key, according to Thomas Holoien in the press release by Carnegie Observatories, was to look for the telltale cosmic burp of bright light that a black hole belches as it consumes its plate of solar spaghetti.
“Only a handful of TDEs have been discovered before they reached peak brightness and this one was found just a few days after it started to brighten; plus, thanks to it being in what’s called TESS’ ‘Continuous Viewing Zone,’ we have observations of it every 30 minutes going back months—more than ever before possible for one of these events. This makes ASASSN-19bt the new poster child for TDE research.”
The “new poster child for TDE research.” What an honor … at least among astronomers. Actually, it’s well-deserved because of ASASSN-19bt’s unusual characteristics. Its home galaxy (2MASX J07001137-6602251, located around 375 million light-years away in the constellation Volans) is younger and more dust-filled than has previously been observed for other TDE events and its growth to extreme brightness was very smooth – unlike the choppiness of non-TDE cosmic events. While the black hole today weighs around 6 million times our sun’s mass, when it was a star it was about the same size as the Sun.
Ladies and gentlemen! Let’s hears some noise for the Tidal Disruptions!