Is Gargantua a black hole or a wormhole?

Question

I will write the events in sequence but in a brief manner. Later on questions will be asked. Correct me if I'm wrong anywhere.

First of all Cooper and his crew go through a wormhole that is near Saturn into another system (Gargantua's system) where they go to Miller's and Mann's planet and after an encounter with Dr.Mann, and after docking with Endurance CASE warns Cooper that Endurance is slipping towards Gargantua's pull. Then a lot happens and Cooper and TARS end up in a tesseract and after relaying the data

1. Is it that "they" the 5th dimensional beings (after the job is done) safely scoop Cooper out of Gargantua (the tesseract actually; which is not in Gargantua's singularity but in the 5D box) and send him back in that 5D box through the extra dimensions back to our solar system through the SAME wormhole through which he came in first to visit Miller’s and Mann’s planet which is also near Saturn?

2. If it is that then why does this timeline show as if Gargantua was used as a wormhole to transport him back to our universe? I mean Gargantua is a black hole and so the picture is misleading right? It also shows the same structure of Gargantua on below left of Cooper station in our universe as it was in the other system (Gargantua's system), but there is ONLY ONE wormhole which has no resemblance with Gargantua’s structure. Am I right?

   

3. See the image, you will find in the poster infographic below that they have written wormhole (which they use to go to Gargantua's system) as a black hole! That is wrong, am I right?

So was the wormhole they came through a "normal" wormhole or actually a black hole? And is Gargantua a wormhole or a black hole? What explains the contradictions between this infographic and how I understood the story, did I misunderstand anything or is this picture just inaccurate?

Answer 1

Yes, you are right, Gargantua is a black hole.

You described the story of the movie quite correctly and it is actually that timeline image you linked that is wrong in some parts and a little inaccurate in other parts.

1. Yes, after falling into Gargantua Cooper lands in the tesseract, which is something of a 4-dimensional represenation of the "Bulk Beings'" 5-dimensional universe, placed there for him by them. And through this thing they send him back to Saturn at the end. It is not entirely clear how exactly they send him back from there. While his "hand shake" with Amelia suggest that the wormhole is involved somehow, it is not clear and that hand shake might as well have happened in some other weird spacetime way.

2. You are totally right, Gargantua is a black hole, not a wormhole and neither was Gargantua directly visible from Cooper Station's side of the wormhole (other than maybe indirectly through the wormhole). The graph is a little inaccurate there when it depicts the black hole both as a wormhole and with one end on the Saturn side. I would think this was just artistically chosen this way to convey that it is the black hole (or more exactly, the tesseract in there) that is used to transport Cooper back to Staturn, however that actual transport really works.

3. Yes, you are right. This is just a plain and clear error in the image. They definitely mean the wormhole there (as it's also drawn that way), which is something completely different from a black hole.

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On a related note, I for myself prefer the second timeline listed here (which also lists the one you got), as it is much more detailed and accurate. It has (what I think to be) a few little mistakes and misunderstandings too, but is overall much more accurate to the timeline and events of the film:

Answer 2

TL;DR The Bulk Beings are so technologically advanced that they could manipulate the Black Hole and Worm Holes like child's play, creating new or modifying them to save Cooper.

According to this Space.com infographic on this Space.com article, sourced from various books, including the accompanying science guide to the movie "The Science of Interstellar" by the movie's physics consultant Kip Thorne:

A wormhole is nothing but an artificially connected set of black holes, which themselves are the creation of massive gravitational forces.

The Bulk Beings, future humans capable of surviving in 5th dimensional space, are shown to have control over gravity in our 3rd dimensional space. To wit, they created the wormhole between Saturn and the Gargantua system. They manipulated time and space so that Cooper could manipulate gravity across time. They plucked Cooper out of a supermassive black hole into a construct, the tesseract, 4th dimensional space.

So there is two easy to consider methods they saved Cooper.

1. They plucked him out of the black hole Gargantua, and send him back through the Saturn wormhole, by manipulating gravity. Think of Cooper becoming a surfer in a pocket of space/air that is his surfboard. Manipulated Gravity and normal space being the wave.

2. Since they are capable of engineering a 1.25 mile wide, 10 billion light year long wormhole, which the above infographic shows is the artificial manipulation of black holes, The Bulk Beings manipulated Gargantua to connect to the Saturn Wormhole and/or a new singularity long enough to drop Cooper off.

To explain the Future Cooper touching Past Brand, The Bulk Beings pulled Cooper and TARS at some point after they pass the event horizon and TARS gets the Quantum Data they need, and before they reach the end of the singularity to their spaghetti deaths. Frankly, Cooper and TARS shouldn't have been able to enter the Event Horizon without dying unless the Bulk Beings were protecting them from the Gravity THE ENTIRE TIME.