I've never really been a fan of Anne McCaffrey; I find her style too earnest. But I've found myself in the middle of a most peculiar argument about her planet, Pern.
For those of you who don't know, Pern is a planet around the star Alpha Sagittarii. Within its system is another planet, the Red Star, that has a highly elliptical orbit that lasts for 250 "turns", or Pernian years. When it reaches perihelion, the Red Star sends a fungus called thread onto the surface of Pern which decimates everything it touches.
And here's where the argument comes in. Apparently McCaffrey classes the Red Star as a "Sedna class inner Oort cloud object". Whether it is or not depends, naturally, on how long a "turn" is. For the Red Star to have a year as long as Sedna's, a Pernian "turn" would have to be 40 years long. And thankfully, that's where I know I can count on you guys.
Alpha Sagittarii, or Rukbat, is 2.3 solar diameters across, 3.2 solar masses, and 112 solar luminosities. So, all I need you clever science types to do is figure out where the star's habitable zone is, and then we can figure out how long Pern's year is.
If you do this for me I'll be very very nice.