Gargantua

"Murphy’s Law Doesn’t Mean That Something Bad Will Happen. It Means That Whatever Can Happen Will Happen."

Gargantua is a very massive, rapidly spinning black hole. It is orbited by the planets Miller and Mann, as well as an unnamed neutron star. A main sequence star Pantagruel was located within a year's flight of Gargantua along with the habitable planet Edmunds. Gargantua is within a several week spaceflight of the Wormhole.

By calculations of Kip Thorne, Gargantua is about 100 million solar masses, placing it firmly as a supermassive black hole. Furthermore, it is an edge case in that it's somehow spun up to maximum minus 0.00000000000001 of the maximum, dragging space around it as it did so. Several of the visual effects were toned down severely from what it would actually look like; the event horizon would be warped and red and blue shifted. Miller's planet would have been under the level of the accretion disk and the event horizon would have covered 40% of the visible sky. By those same calculations, orbital transfers to Miller's would likely require slingshot maneuvers around intermediate mass black holes at both the start of maneuvers and at the end, as the energy requirements seemingly preclude other methods of getting the required energy. Partially alluded to in movie by the short reference to a neutron star being useful for slingshot maneuvers.