A future Test-Pilot stranded at the fare side of the Galaxy trying to find a way home while solving the mystery of a black planet.

Normally the word 'Stranded' is a good word to use. If someone is 'stranded' on a desert island, we get a picture of the situation.

But in the specific case of this logline, you need just a word or two more.
I decided to think, off the top of my head, reasons why a pilot might be stranded.

1: His spaceship ran out of fuel.
2: His spaceship broke down.
3: His spaceship blew up.
4: He was captured by aliens
5: The mysterious black planet interfered with the workings of his spaceship.

Since the mysterious black planet seems to be the hook of your story, I would go with number 4 and connect why he is stranded directly to the mysterious black planet.
Now the lead must explore the black planet if he is to stop the interference and complete his goal of getting home.

The term, "A future Test-Pilot" could be read two different ways, might want to change that for clarity.
Because no matter how illogical it may seem, if a sentence can be read the 'wrong' way, it will be.

As variable said, a logline (and script) must be built on the spine of one primary action toward achieving one overarching objective goal.? All other actions are vertebrae to achieving that one goal.

And what is there about the black hole that makes it a mystery that MUST be solved?? Or else what?? What's at stake if he doesn't solve the mystery??