From the July 2020 issue

In what part of the electromagnetic spectrum does the Sun emit energy?

By | Published: July 9, 2020 | Last updated on May 18, 2023
The Sun appears here in ultraviolet light, which has a wavelength slightly shorter than that of visible light. Looking at the Sun in this portion of the electromagnetic spectrum highlights its delicate — and extremely hot — outer atmosphere, the corona.

Q: In what part of the electromagnetic spectrum does the Sun emit energy?

Jason Perry 
Phoenix, Arizona 

A: The Sun emits light in virtually every part of the electromagnetic spectrum, albeit some more than others. The sunlight that we see — aptly named visible light — falls into only a very narrow range of the spectrum, from about 400 to 750 nanometers (a nanometer is one-billionth of a meter, or about 400 millionths of an inch). The Sun also emits at longer wavelengths, in the infrared, microwave, and radio. Our Sun emits light at progressively shorter wavelengths, too: the ultraviolet, X-ray, and even gamma-ray parts of the spectrum.

But most of the Sun’s light is in the infrared, visible, and ultraviolet parts of the electromagnetic spectrum. Its output at the longest (radio) wavelengths is much less than its output at visible wavelengths; conversely, the Sun’s short-wavelength X-rays come only from the hottest and most active parts of its outer atmosphere, the corona. The gamma rays our star generates through fusion processes in its core never make it out of the Sun before they are converted into lower-energy light. So, the only gamma rays from the Sun we receive here on Earth are from extreme solar events, such as the most powerful solar flares.

Alison Klesman 

Senior Associate Editor