Convert Sun's Radius (R☉) to Femtometer (fm) instantly.
About these units
Sun's Radius (R☉)
The Sun's radius is approximately 696,340 km, representing the distance from the Sun's center to its photosphere. This measure is essential for understanding solar structure, luminosity, and energy output. Stellar astronomers use the Sun's radius as a benchmark for comparing other stars, often expressing their size in multiples of R☉. Precise knowledge of the Sun's radius aids in modeling solar evolution, predicting solar cycles, and calculating irradiance impacting Earth's climate and space weather. It serves as a fundamental scale for both astrophysics and heliophysics.
Femtometer (fm)
A femtometer, equal to 10⁻¹⁵ meters, is the scale at which the structure of atomic nuclei becomes measurable. Also known historically as a "fermi," this unit is used extensively in nuclear physics to describe the radii of protons, neutrons, and nuclei, which typically span 1–10 femtometers. At this scale, the strong nuclear force dominates interactions, and classical intuition breaks down almost entirely—quantum mechanics provides the only meaningful framework. The femtometer also plays a role in high-energy particle experiments, where the wavelengths of probing particles (like high-velocity electrons) may be expressed in femtometer increments. These small wavelengths allow researchers to resolve sub-nuclear structures. While invisible to any optical instrument, distances in the femtometer range can be inferred through scattering experiments, such as those performed in particle accelerators.