Extraterrestrial Life/Requirements For Life

Below, the requirements are listed.

Star

For a star to be able to host habitable planets, it must:

This section is unfinished.

For a planet to be habitable by life similar to that on Earth, it must:

have a temperature that stays between -15°C, below which chemicals start reacting too slowly for life to occur and water freezes, and 115°C, above which protein and carbohydrate molecules, as well as genetic material, start to decompose and water evaporates.
be at just the right distance from the star so it gets enough energy from the star.
have continuous liquid water on its surface.
enough mass for radioactive heating, which allows for geological activity.
a thick atmosphere to protect the planet, stabilize its climate, and provide sufficient pressure to hold liquid water. However, it must not be so thick that it creates a greenhouse effect that makes the planet too hot.
not be too close to massive planets which can divert asteroids towards or strongly perturb its orbit.
have a massive planet well outside of its orbit that diverts dangerously large asteroids away from it.

This section is unfinished.