Types of Light from the Sun
There are two main types of energy that come from the Sun. These include visible radiation, which we perceive as light, and invisible infrared energy, which we sometimes think of as heat. Both visible and infrared radiation are part of the electromagnetic spectrum, which includes all the types of energy released by the Sun.
The Light We See
Think of a picture of the Sun taken from space, and compare it with an image of the Sun from Earth. In both images, the Sun appears as white light, which is the result of all of the colors mixed together. The light we see from the Sun comes from the very hot temperatures of its surface, or photosphere. Although astronomers classify our Sun as a yellow dwarf star, its surface is visible to our eyes as white light, from the combination of all the colors in the visible part of the spectrum.
Sometimes, water droplets or ice crystals in the atmosphere create an optical phenomenon to help separate the light into its spectrum of colors. A rainbow is a prime example of this phenomenon, caused by raindrops in the sky essentially acting as a prism to split the light into its component wavelengths.
Ice crystals high in the atmosphere can also separate sunlight into its component colors. Many of the neat light effects we see in the sky, like sun dogs, haloes, and iridescent or polar stratospheric clouds, result from ice crystals scattering light into its individual colors. The colors of light visible to our eyes each radiate at a unique wavelength within the full electromagnetic spectrum.
The Light We Don’t See
Other types of energy, or light, from the Sun, are at wavelengths that our eyes cannot see. These energy types include infrared radiation and small amounts of ultraviolet radiation, x-rays, and gamma rays.
Scientists study the energy released by the Sun at different wavelengths to learn more about the Sun’s properties, including what the Sun is made of and how hot it is. Different regions of the Sun have different temperatures, so looking at the Sun in different wavelengths allows scientists to view those regions and their features. For example, the image below from the NASA Solar Dynamics Observatory shows the Sun at 13 different wavelengths, which helps scientists study the parts of the Sun or view specific solar features, like a solar flare.
Scientists add bright colors to help make solar images visible to the human eye, especially for wavelengths that would otherwise be invisible. When we see a picture of a neon green or bright red Sun, we know the image is based on some non-seeable version of light, like extreme ultraviolet radiation or x-rays. Even visible light images of the Sun’s surface, which would appear white or sometimes light yellow through a telescope, are typically colored darker yellow to provide a better background for discerning sunspots and other features.
These two images of the Sun were taken at nearly the same time on February 3, 2002. The image on the left shows the Sun’s surface) in visible light. The image on the right shows the Sun in ultraviolet (UV) light at a wavelength of 30.4 nanometers (304 Ångstroms). The Sun’s lower atmosphere (chromosphere) shows up especially well in this UV wavelength. Bright areas in the UV image reveal hot, magnetically disturbed regions in the chromosphere that correspond to the locations of sunspots in the visible light photo.