The Planets

Planet #1

The first planet that orbits the Star is a tiny, hot terran planet. It is only 0.131 times the mass of Earth, and 67.913% of that mass comes from its iron core alone. It has a density of 6.468 g/cm², and has roughly half (0.481 times) the radius of Earth. Its gravity is 5.541 m/s², a little over half of Earth's gravity. It has only 4.8 degrees of axial tilt, so it experiences almost no seasonal variation in temperature. It orbits 0.18 AU away from the Star, which contributes to its alarming average surface temperature of 582 °C (~1080 °F). (Of course, another contributing factor would be its bond albedo of 0.079.) It has no atmosphere, which certainly doesn't help things! Its inclination is 4.3° relative to Isuja. It is tidally locked to the Star, so the same sun-baked side always faces toward it. It takes 69.356 Earth days to complete one orbit around the Star (this is also the length of one day). It has one small moon, which is a captured asteroid. This moon is very small, but it orbits very close to the planet, resulting in what would be very strong tides if there was water on the planet.

Isuja

Isuja is the second planet that orbits the Star; it orbits at 1.60 AU. It is slightly more massive than Earth (1.261 Earth masses). 34.63% of that mass comes from its core; the average density of Isuja is 5.804 g/cm². Isuja's radius is 1.062 times Earth's, and its gravity is 10.964 m/s². It has 41.47 degrees of axial tilt, so seasonal variation is very significant on Isuja. One day on Isuja lasts 21.370 hours. Isuja has a bond albedo of 0.322, meaning that it's just slightly more reflective than Earth is. The Isujan year is 660.023 Earth days long, or 739.227 Isujan days.

Planet #3

The third planet that orbits the Star (at 3.14 AU) is much larger than Isuja or Earth ─ its mass is 2.731 Earth masses, giving it a radius of 1.324 Earth radii and gravity of 15.289 m/s². It has 22.826 degrees of axial tilt, giving it roughly the same seasons as Earth, in everything but the temperature. The third planet has a thin atmosphere, composed primarily of carbon dioxide. It is far enough from the Star that, if it had no atmosphere, it would have a temperature of around -68 degrees Celsius (-90 °F). However, due to all the carbon dioxide, its average surface temperature is actually 11 degrees Celsius, which is 52 degrees Fahrenheit. Its inclination is -2.11° relative to Isuja. Its year is 1786.589 Earth days.

Planet #4

The fourth planet in Isuja's solar system is a small, icy world. Imagine if Mercury orbited where Mars is. It's 6.100 AU away from the Star, and it has an extremely thin atmosphere. It is 0.687 times the mass of Earth, so it's smaller, but its dense iron core, which contributes 72.812 percent of its mass, means that it actually has almost exactly Earth gravity (1.001 times Earth). Its surface temperature is -131 degrees Celsius (-203.8 degrees Fahrenheit). It takes 13.244 Earth years to complete one orbit around the Star. It is inclined 9.13 degrees relative to Isuja. It has the relatively low bond albedo of 0.192.

Planet #5

The fifth planet is a large gas giant, rather like Jupiter. It orbits 25.92 AU away from the Star, so it takes 116.007 Earth years to complete just one orbit. It spins in a retrograde manner, so the Star rises in the west and sets in the east. Remarkably, it is 197.913 times the mass of Earth. Its core is small relative to the overall planet, taking up only 5.124 percent of its mass. Despite the huge mass, the fifth planet is actually only 4.424 Earth radii in width. However, it is extremely dense, weighing 12.595 grams per cubic centimeter (on average). This gives it its immense gravity of 99.175 m/s². Its inclination relative to Isuja is -5.10 degrees, and its bond albedo is 0.371.

Planet #6

The sixth planet is a smaller gas giant, 47.54 AU away from the Star. It is small, only 9.637 Earth masses. 4.819% of the mass comes from its core. It's a little less than twice Earth's radius, and is inclined 9.140 degrees on its axis. It falls almost perfectly in line with Isuja, having an inclination of -0.03 degrees. This planet, as well as the seventh, is invisible to the naked eye from Isuja, and would not be known as one of the planets until modern times.

Planet #7

The seventh planet is the furthest planet away from the Star. It is 94.90 AU away from the Star and orbits at the inclination of 14.12 degrees (relative to Isuja). It is 13.923 Earth masses, comparable in mass to Neptune. It has effectively no seasons, due to its 0.142° axial tilt. Its density is 7.746 g/cm³, and it is only 2.148 Earth radii. More than anything else, the seventh planet is cold: its average temperature is -232 degrees Celsius, which is ─ wait for it ─ negative 386 degrees Fahrenheit! It takes 812.704 Earth years for this planet to orbit once, so it seems to hang in one spot in the sky when observed (through a telescope, of course).