Solar Radiation | Universe Today

Written by Fraser Cain

Sunlight, or solar radiation, is all the electromagnetic radiation given off by the Sun. Here on Earth, our atmosphere filters the Sun's light, protecting us from harmful radiation and changing the color of sunlight. Let's take a look at all of the wavelengths of light in the solar radiation.

But first, let's look at where this radiation comes from. As you probably know, the intense temperature and pressures at the core of the Sun is where the magic of solar fusion happens. Protons are converted into helium atoms at a rate of 600 million tons per second. Since the output of this process has lower energy than the protons that began, the fusion gives off a tremendous amount of energy in the forum of gamma rays. These gamma rays are absorbed by particles in the Sun, and then re-emitted. Over the course of 200,000 years, photons of light make their journey through the radiative zone of the Sun and out into space.

The surface of the Sun we can see is called the photosphere, and it's the point at which light from the Sun can finally escape into space. Through their long journey through the Sun, however, the photons have lost energy, and become other wavelengths of light. That's a good thing; otherwise, we'd just have gamma rays streaming from the Sun.

Solar radiation isn't any one kind of light. It's actually a mixture of different wavelengths. The heat we feel from the sun is infrared, and ranges in wavelength from 1400 nm to 1 mm. Visible light than ranges from 400 to 700 nm. Out in space, the Sun's light appears white, but here on Earth we see it as more yellow because the atmosphere deflects blue and violet photons more easily. We're also hit by ultraviolet radiation; fortunately, much of this is absorbed by the Earth's atmosphere as it's quite dangerous to life.

All life on Earth depends on solar radiation. It's the primary source of energy to the Earth, and drives the planet's weather and ocean circulation. Without this source of energy, the Earth would freeze, and only its internal geothermic heat would stop it from freezing into a solid rock.

We have done many articles about solar radiation on Universe Today. Here's an article about how solar radiation concentrates during solar storms. And here's one about how spacecraft are protected from solar radiation.

Here's an article from NASA about solar radiation.

We have recorded an episode of Astronomy Cast just about the Sun called The Sun, Spots and All.

Filed under: Astronomy