Star Types

In Iridium Moons, Hyperspace drives only function in regions where spacetime is sufficiently flat, which is to say they do not work in the presence of strong gravitational fields as the ones produced by stars. When too close to a star, a ship can not activate its Hyperspace drive, and any ship in Hyperspace will automatically jump back into normal space once it gets too close to a star for the Hyperspace drive to work. How far away a ship has to be to use its Hyperspace drive depends on the mass of the star. And the time it takes for a ship to get sufficient distance from a star depends on its speed and the distance between the star and the planet it took off from.

The time that it takes for a ship to move through normal space to reach a planet after it comes out of Hyperspace, or to jump into Hyperspace after taking off from a planet, often takes several days or even weeks. Time which can be very important to determine if character can reach their destination before it is too late, or which their enemies can use to send messages to their allies to prepare for their arrival. As such, knowing both the distance from the star where ships enter and exit Hyperspace, and the distance a destination planet has from its star can be very important. For space stations and lifeless planets, the distance to the star can be anything. But for planets with plant and animal life on them, the possible distances at which the energy from the star is not too intense or too weak is much more restrained.

The table below shows main sequence stars sorted by mass, which is the main defining aspect of main sequence stars.
The first three colums show the star's mass, radius, and amount of energy it radiates into space (luminosity). All the values in these columns are converted to masses of the Sun, radius of the Sun, and luminosity of the Sun, so for the Sun all these values are 1.
The fourth column shows the star's type and color.
The next columns show the minimum distance an Earth-like planet needs to have from the star without getting boiled, and the maximum distance it can have without getting completely frozen. The gasses in the planet's atmosphere and its ability to reflect light back into space can make huge differences for the local temperatures, and of course temperatures can vary greatly between the equator and the poles, so you can still have cold planets near the minimum distance and hot planets near the maximum distance, or anywhere inbetween. Hyperspace minimum shows the minimum distance a ship must have from the star to use a Hyperspace drive. The numbers for each column are in Astronomical Units, which is the distance between the center of the Sun and the center of the Earth. It is a simple and intuitive unit for comparison and used by the Coriolis rules for space travel.
The final colum shows how large a star of the given radius would appear in the sky as seen from a planet that receives the same amount of energy from its star as the Earth gets from the Sun. It shows the angular diameter in degrees, as well as the apparent diameter of Sun in brackets. (Larger stars would actually look smaller in the sky for Earth-like planets. Even though they are larger, their luminosity becomes much more intense, so you have to be even farther away to get the same amount of brightness.)

The next table shows how common the different types of stars are in the universe. Abundance shows the percentage of main sequence that are of the given type, and the Binary column shows the likelihood of such a star being part of a binary pair. Systems with three or even more stars are possible, but it seems very improbable for planets to exist with three or more suns in the sky. If more than two stars are close together, the complex gravitational interactions between them would make stable orbits for any planets nearly impossible, and if any third or further stars were sufficiently far away to avoid this problem they would probably look more like planets in the sky than like another sun. As such, Iridium Moons only has planets with either one or two suns.

The vast majority of planets that characters would have any reason to visit would probably be K-type orange stars, as they are by far the most likely to produce planets with native life on them. They are quite common, very long lived with a lot of time for life to evolve, and produce little problematic radiation that might be hostile to life. The next most common type of suns would be G-type yellow stars like the Sun. They are not very common and only last half as long as K-type stars, but they are perfectly capable of supporting inhabited planets. F-type yellow-white stars can also have planets that support life, but they would be even more uncommon that G-type stars.
M-type red dwarfs make up around half of all stars in the universe. However, many of these stars are known to occasionally produce heavy bursts of high energy radiation that would likely kill any life on planets close enough to have Earth-like temperatures. While planets around red dwarfs would only rarely have any native life on them, they are very well suited for pure mining operations, as the star's low gravity allows ships to land and leave very quickly.
A-type white giants and B-type blue-white giants are very rarely seen as the sun for any settled planet. They are not only very rare stars, but are very short lived and unlikely to have planets with even microbial life on them before they explode as supernovas. Mining in them is possible, but for A-type stars, ships would take twice as long to land and leave the system again than it takes for red dwarf systems, and it gets even worse than that in B-type systems.

Another type of star that characters might visit are white dwarfs. These are the remains of dead K, G, and F-type stars. They are nothing more than the burned out cores of the stars they used to be, which still glow white hot but don't produce any further energy. Before their death, they would have completely destroyed any planets close to them and striped those further out of their atmospheres. On any such planet, they would look like a very bright star instead of a sun, but one so bright that it still produced dim daylight on the surface. A red dwarf has a mass of about 0.6 times the mass of the Sun, which means it has a minimum distance of 23 AU for hyperspace jumps.

On the other end of the extreme are red giants. These are stars that have ended the main sequence phase and bloat up to many hundreds or thousands of times of their original radius. This destroys any life on planets that would previously been habitable, but this process is slow enough to have no effect on any mining operations farther out in the system. While most stars become red giants at the end of their lives, this is only a relatively short phase of their existance, and as such they are not very common.

For the New Frontier, the distribution of star systems is like this:

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