Solstice And Appearance Of Sun In Different Wavelengths

Solstice and wavelength cover

Sun, the life source of most lives on our planet. Sunlight is essential not only for our survival but also for our health, as it provides us with crucial vitamin D and enhances our mood by its healing and soothing nature, especially during the winters. Our Sun is truly important to us and many cultures celebrate our position to the sun and solstice are the two days that truly tell us about the shift in seasons. As for the light itself, you might be surprised to know Sun is not actually yellow.

What is Solstice?

As we know there are four seasons on our planet (depending on where you live) and these seasons occur thanks to the tilt of our planet on its axis and this tilt happens twice a year at an angle of 23.5°. If Earth was not to tilt on its axis, we’d have no seasons as sunlight would directly shine on the equator. Solstices represent or tell us the farthest point in the northern and southern hemispheres where sunlight shines from the equator. The first solstice occurs during the 20th or 21st of June and this is known as the summer solstice which marks the start of the summers and is the longest day of the year. The winter solstice happens on 21st or 22nd December that is considered as the beginning of the winters and is the shortest day of the year.

Solstice simple

An illustration of Summer Solstice.

Sun in different wavelengths

Light is truly a wonderful thing, as it is light that enables us to see everything around us, and without it, we wouldn’t be able to observe anything whatsoever. While Sun may appear yellowish-white to the naked eye, that is not exactly how Sun appears in reality. To understand that we must understand the concept of wavelength and spectrum of light. Firstly, we are able to see the Sun because of the light that is produced by its heat that is generated by various gases burning up on the surface of the Sun. The electromagnetic spectrum is huge with varying wavelengths, it consists of x rays, cosmic rays, microwaves, infrared, ultraviolet, radio waves, gamma, and finally what we are able to see with our eyes the visible light. As for the wavelengths, it is the distance between each successive crest and trough of a wave and it determines the color of the light, and a combination of all the wavelengths results in white light. Now you can imagine, firstly, the sunlight that we see is a tiny part of a huge spectrum, then the wavelength of photons determines its color. So what possibly be the true color of Sun?

Electromagnetic spectrum

The electromagnetic spectrum.

NASA utilizes specialized cameras and instruments either in the ground-based or space-based telescopes that captures the images of the Sun in varying wavelengths to determine various gases and composition of the Sun to get its complete picture. As mentioned previously, heat is the reason why light is produced, however, Sun consists of different atoms and the main ones are helium and hydrogen, these atoms have varying electrical charges which emit light of specific wavelengths as well and all the light produced by the Sun is measured in Angstroms, which is a unit of length equal to 10−10 meter or one hundred-millionth of a centimeter and is used to determine wavelengths. This helps scientists determine the temperature of gases or molecules by measuring the wavelength, for example, at 5500 Angstroms a material is usually burning at 5700°c observed by yellow-green light. You might be wondering why bother with all of this? Because this allows scientists to understand how the particles and heat generated move through the Sun’s atmosphere.

NASA Solar dynamic observatory

NASA’s Solar Dynamic Observatory (SDO).

Three main telescopes are used to carry out this process, these are NASA’s Solar Dynamics Observatory (SDO), NASA’s Solar Terrestrial Relations Observatory (STEREO), and the ESA/NASA Solar and Heliospheric Observatory (SOHO). Specifically, the SDO had helped researchers produce images of the Sun that were never seen before and it measured 10 different wavelengths.

  • 4500Å: Shows the Sun’s surface.
  • 1700Å: This shows the atmosphere of the Sun known as the chromosphere, which lies just above the surface.
  • 1600Å: The combination of the Sun’s surface and the transition region, that is between the chromosphere and the upper layer of the Sun’s atmosphere known as Corona.
  • 304Å: The light emitted from the chromosphere and transition region.
  • 171Å: Sun’s atmosphere again but when it is quiet.
  • 193Å: Shows the hotter material of a solar flare.
  • 211Å: The wavelength that shows the magnetically active region in the Sun’s corona.
  • 335Å: Slight variation but it shows a similar region as mentioned before.
  • 94Å: Highlights the regions of the corona during a solar flare.
  • 131Å: The hottest material in a flare.
Sun wavelength chart

Sun at varying wavelengths.

Solstice doesn’t have much effect on how Sun is observed on the Earth, while it changes the seasons it doesn’t alter the way we see sunlight. But one cannot deny the mesmerizing images that make the Sun appear as a completely different star.


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