If I remember correctly Nolan consulted with some actual astrophysicists to get it right. Furthermore, they managed to make use of the Hollywood-funded super computer time to get some actual science out of the deal.
Here's a random article I googled discussing the topic: https://www.wired.com/2014/10/astrophysics-interstellar-blac...
Not just any astrophysicist. It was Kip Thorne, who was already an authority in general relativity even before he received the Nobel prize in 2017 for his work on gravitational waves. His works on the movie led to the publication of a scientific paper: https://aapt.scitation.org/doi/10.1119/1.4916949
I was working at the visual effects studio responsible (Double Negative) at the time. I didn't work on that project but it was pretty cool work they were doing, and was in close collaboration with Kip.
