Parts of the Earth's surface that are not desert. A part of the solar system where major impacts are rare. Any Earth-like planet around a star. The two most abundant elements in the Sun are iron and oxygen. The particles must be part of a very hot gas or plasma.
Reactions occur more rapidly when the density is high.
Two protons must approach each other at high speed. The particles must spiral around a strong magnetic field. Nuclear reaction rates in the core of the Sun remain steady because conditions adjust to counteract any tendency for the reaction rate to change. The mass of the Sun is about equal to the combined masses of all the planets. Studies of sunquakes, or heliosiesmology , have revealed that the Sun vibrates only on the surface.