My husband has been re-watching Game of Thrones. As I've said before, I don't like political intrigue, nor a cast of thousands, so this is not my cup of tea. But the characters mention they are ending a summer of 500 years, and the winter will soon be on them. That comment has me intrigued.
What kind of solar system would they be in that a season could last for hundreds of years?
I read a book many years ago - I don't remember the title or the author, sorry - where the planet's orbit was a lop-sided elliptical around its sun. When winter came, everything hibernated, even the people. The length of their year did not equal one of ours, but a year - one revolution around their sun - did involve seasons. So that wasn't the answer.
I then thought about the planet NASA has discovered that has 4 suns. That in itself is mind-boggling. The planet revolves around one star, which is in a mutual revolution with a second star, and that pair of stars is in a mutual revolution with another pair of stars.
I don't have enough math and physics to do any computations, so I just have to use some logic to try and get a feel for it. The first pair of stars have to be far enough away from each other that they don't tear each other apart, and also so they don't burn the planet to a crisp when it passes between them. But when that planet is between them, it would be extra warm. As the stars go around each other, that extra warmth would move around their calendar, until the 'extra warmth' was actually during their winter. It might not seem like they were having any winter.
How long would it take for this 'extra warmth' to move around the planet, from producing warm autumns through not-really winters and into warm springs? I don't know. It would depend on how long it takes for those 2 stars to revolve around each other. A thousand years might be too fast.
That might help explain a REALLY LONG summer, but it doesn't explain an equally long winter. When both stars were on the same side of the planet, they would have hot summers and cold winters. Bummer. I thought I might be on to something.
Do we have any physicists in the audience who would like to weigh in on this?