[nudephil (OP)]

Here's a question from listener David:

Can we be certain that black holes still exist?

What's the evidence?

[Janus]

https://www.nasa.gov/mission_pages/chandra/news/black-hole-image-makes-history

[evan_au]

Yes.

For many years.the Max Planck Institute has been observing massive stars at the center of the Milky Way galaxy using infra-red telescopes  They have observed long enough to plot the course of a number of bright stars orbiting the supermassive black hole at the center of our galaxy, and this has allowed a quite accurate measure of its mass.
See: https://www.mpe.mpg.de/6590570/Stellar-Orbits

Recent work has even shown that one of these stars, S2, is showing gravitational precession, as predicted by the general theory of relativity:
See: https://www.mpg.de/14692117/detection-of-schwarzschild-precession-in-the-orbit-of-star-s2