A femtometer (fm), also known as a fermi, is an extremely tiny unit of measurement used to express even smaller distances than a picometer. It is equal to one quadrillionth of a meter, which is 0.000000000000001 meters or 1 × 10^-15 meters. The prefix "femto" denotes a factor of 10^-15 in the International System of Units (SI).
Femtometers are typically used in the field of nuclear physics and particle physics to describe the sizes and distances involved in atomic nuclei and subatomic particles. The nucleus of an atom, for example, is on the order of a few femtometers in diameter. In high-energy physics experiments and discussions about fundamental particles like protons, neutrons, and quarks, femtometers are a relevant unit of measurement due to the incredibly small scales involved.
The Sun's radius, often denoted as "R☉," is the distance from the center of the Sun to its outer edge or surface. The Sun is not a solid object but a massive, hot, and highly compressed ball of gas, primarily hydrogen and helium.
The average or mean radius of the Sun is approximately 696,340 kilometers (about 432,685 miles). Keep in mind that the Sun's outer boundary is not sharply defined, and its structure consists of different layers, including the core, radiative zone, convective zone, and the visible surface known as the photosphere.
The Sun's radius is a fundamental parameter in astronomy and solar physics and is used as a reference point for measuring distances within the solar system and studying the properties and behavior of the Sun.