Post making contest 6.0

This is puzzle #3: Dispatches From The Outer Cosmos

CLUSTER 2016/17
BRIGHTEST STAR: F2IV/V
NOTEWORTHY PLANETS:

• This planet is often overlooked in favour of a potentially habitable Earth-sized world orbiting four and a half times further out, but this one's the largest in the system. On the other hand, it's home only to a trio of animals, one of whom is constantly seeking to expand its menagerie ménage à trois...
  
• Not much is known about this planet - it takes just 94 hours to complete an orbit (semi-major axis 4.5 million miles) about its rotationally variable parent star, and is the smallest of three. Its natives however, disseminated throughout the galaxy, are notorious for getting het up over simple card games, and are thus very much known about.

CLUSTER 2017
BRIGHTEST STAR: F5IV/V
NOTEWORTHY PLANETS:

• Remarkably, the planets of this system all orbit in the same plane, aligned with the rotation of its K-type star. The inhabitants of the outermost (which, actually, is only out at ~0.5AU) are very serious about two things above all else: consensual sex and constant questioning. Their development of interstellar travel caused no end of headaches...
  
• Orbiting a metal-rich red dwarf every five days, this "mini-Neptune" has a radius roughly two and a half times that of Earth's. One of its moons is a dedicated psychiatric hospital for strangely-disguised squirrels, run by the sole remaning member of the native species.

CLUSTER 2016
BRIGHTEST STAR: K3III-IV
NOTEWORTHY PLANETS:

• This lava world found fame in its hellishness; being so close to its parent star, it zips around it in just eight and a half hours and has a surface temperature of ~2500K! Its inhabitants place great value in cold things, which is somewhat understandable, and some partake of a peculiar ritual involving frozen hydrogen, which really isn't.
  
• Orbiting around 73.5 million miles from a Sun-sized star, this Neptune-esque planet was long ago the cradle of a race that lived in sophisticated constructions towering above its solid core. Nowadays, a religious sect from a neighbouring star sail about its atmosphere in search of these...

CLUSTER 2015b
BRIGHEST STAR: K3III
NOTEWORTHY PLANETS:

• Here's a planet orbiting a star that's ascending the red giant branch - in other words, it's expanding and will engulf this planet in about 55 million years. In light of this, its entire population has dedicated itself to what they hope will be their legacy: an explosive that will tastefully rearrange at least two rooms of your house. Well, it keeps them happy...
  
• This planet has a circumbinary orbit about its parents, despite doing so rather closer than what should have been inner limit for planet formation about a binary star. Being roughly half gas and half rock and ice, it's not the most liveable of places (especially not at an average temperature of 188K!), and indeed its residents refrain from grumbling only because of the ballistic devices (assigned by the government to each and every individual) that keep them very much in line...

CLUSTER 2015a
BRIGHTEST STAR: A1
NOTEWORTHY PLANETS:

• Another gas giant with a circumbinary orbit, this about a pair dwarfs. What sets this one apart is just how wobbly it is, with the tilt of its spin axis varying by about 30 degrees every eleven years or so! The two lovers that staff the research ship in its atmosphere constantly bicker about the future of their feline companion, with one of them hopeful it might join a posse... the other is not so sure...
  
• This planet does not exist. In this system, there's a planet at 5.7 million miles, another at 10.5, and then... nothing. Certainly not another three more planets, that's for sure. And yet, legend has it that, once upon a time, at the fringes of this system lay a world in the grip of a biomechanical empress, whose literal iron fist prevailed for thousands of years. Upon her inevitable corrosion, a monument was erected both to and from her in perpetual polar grimace... but, in the absence of the relevant planets, surely this can only be myth?

End of message.