Determining where your world is in the galaxy can be a task not paid attention to, or it can be a matter often glossed over. However, if you're planning the logistics of a science fiction roleplay and setting up intergalactic travel, the topic has a fine chance of manifesting. Even if not, if you're creating your own planet and you wish to have every detail plotted, taking the time to think about where your planet is will add a depth to the ecosystems and atmosphere. In this section of "Building a Planet", I'm going to discuss the type of star the planet orbits.There are several options for this. There are, after all, so many types of stars! This can affect your planet more than you might realize and is worth taking into consideration. Some examples are: red dwarfs, red giants, and yellow supergiants. Red dwarf stars have a low mass compared to many other stars, as well as a low core temperature. Because of this, nuclear fusion occurs as a fairly slow rate and these stars give off little light. The low level of light and heat would mean that any planet in the "habitable zone" (for humans, anyway!) would be so close to the planet that it would be at a high risk of being tidally locked (not good for a planet, since this means one side of the planet would always be facing the star, much like only one side of the moon faces Earth, thus causing one side to always be experiencing "nighttime" and the other in perpetual daylight). The zones cause by this would create vastly differing temperatures, one extremely cold and the other very hot. Theories about about habitability in these conditions via a water mass to circulate heat or migration of a species. Red giants are stars whose core has been depleted of its hydrogen and has thus switched to thermonuclear fusion. They have an enormous outer atmosphere and radius but have a low core temperature. The inner core of the star is contracting and a shell is formed outside which results in the star heating up once more, causing the large radius and the outer layers expand. Red is actually a cooler color as far as heat is concerned and the color is due to the exhausted core of the star attempting to heat a larger surface area, making the planet a lower color on the heat spectrum, even though it has become much hotter as the core shrunk. This means that the "habitable zone" for life forms we know of will be pushed back, since the star is expanding AND getting hotter. Yellow supergiants are unstable. They have a high luminosity and temperature, which renders them thus, as well as their sheer size. Supergiants tends to have higher amounts of heavy metals than other stars and because they burn through helium and into the heavier elements (even up to iron), in addition to their size, they will end up a supernova. To exist orbiting a star of these conditions, planets orbiting one would most like have to be incredibly large and very dense to avoid being swallowed or disintegrated by such a star. There are so many other stars out there, with their own unique conditions and restrictions! I encourage you to pursue more knowledge when you're building a planet and to consider what type of planet it would need to be in order to orbit a given star and what type of life would exist on such a planet.