I'm a musician interested in astronomy and physics and all, but I have very little scientific background up to date in those fields, so I come here for a little help.
A fiction I wrote, called "The Night" involves a night that is at least 70 years long, and while the planet's inhabitants believes it is some kind of apocalypse, end of time, or God's will, I wanted to find a solid background where such night, while not being frequent, could happen.
First, I thought that a planet orbiting a brown dwarf, itself orbiting a main-sequence star, could experience periods of "more than total" eclipse and be in the umbra of the brown dwarf for some time. In order to last 70 years, though, the orbital period of the planet would have to be insanely great, so I thought it'd be implausible.
Then I came across some info about Epsilon Indi A, who is orbited by E Indi Ba, a brown dwarf, which is orbited by another brown dwarf, E Indi Bb. The problem is that E Indi A is a red dwarf, and E Indi Ba is at 1500 AU of it, and that means that if a planet orbits E Indi Bb (which is at approximately 2 AU of Ba), it would receive so little light (and heat!) from the main star that it would be night almost all year long, even if the radiative heat from the two brown dwarves might make some life possible. The planet needs to experience day in order to have night, too. So that system's out.
And I thought that a similar system, albeit around a larger star (maybe G or F), and closer than the 1500 AU of E Indi Ba. Even if the orbital period of a planet surrounding the analog to Bb would not be insanely long, it would be possible to experience longer than habitual nights in special circumstances.
Could we also include super Jupiters, closer to the main star that could also eclipse it from the point of view of the planet, in order to extend the "night" to an ultimate degree, where such circumstances occur only once in a billion years, let's say.
Can anyone help me a little?
Thanks a lot!