Clouds in the sky, or too many city lights.
This question cannot be answered as both criteria are different. See related questions.
A Supernova. See related question
No, Australia cannot see the North Star in the night sky because it is located in the northern hemisphere and is not visible from the southern hemisphere.
The whole of the universe is made up of single stars, so your question is not that clear. You may be referring to the first start you see at dusk, which is probably Venus, which is in fact a planet. You may even see Sirius, the bright star in Canis Major. To see just a single star has no specific meaning unless you want to put a meaning to it youself, in that case you have all the meanings in the world to choose from.
No. As you have no doubt noticed, you cannot see the stars during the day.
It is easy. A single event cannot be any of the things mentioned in the question.It is easy. A single event cannot be any of the things mentioned in the question.It is easy. A single event cannot be any of the things mentioned in the question.It is easy. A single event cannot be any of the things mentioned in the question.
Multiple questions in a single question. See related questions.
Whose single season has no
You can see Venus, as the morning or evening star. It's especially bright at those times.
The closest would be the pistol star with a radius of about 300 -> 340 times that of our own Sun. See related link for more information.
The North Star is almost directly over the north pole, so it cannot be seen south of the equator.
there are names for the constellations but I'm not sure about every single star