[Music throughout]On January 21, 2019,
for the very first time, NASA’s TESS saw a black hole destroy a star.
This was a tidal disruption event, which occurs when a star
passes too close to black hole. Extreme gravity causes
the star to bulge and break apart into a stream of gas.
The tail of the stream escapes into space, but the rest swings around
to form an accretion disk. This event,
called ASASSN-19bt for the All-Sky Automated
Survey for Supernovae, which first identified it, happened in the TESS
continuous viewing zone. TESS’s four cameras scan large
sectors of the sky, and one constantly monitored this region for a full
year. TESS saw ASASSN-19bt
as soon as it started to brighten, days before other observatories
spotted it. NASA’s Swift satellite
quickly observed the outburst in visible light, UV,
and, along with the European XMM-Newton satellite, X-rays.
The UV measurements are the earliest recorded
for a tidal disruption to date. They showed the event’s temperature
dropped almost 50% in just a few days. Such a steep
decrease has never been seen in a tidal disruption before.
These outbursts are rare, happening only 
once every 10,000 to 100,000 years in a galaxy
like our own. Future discoveries will help us
learn even more about these uncommon cosmic blasts.
[Music][Explore: Solar system & beyond]
[NASA]
