Former NASA astronaut Scott Kelly has confirmed an age-old debate: is the sun yellow or white? This must have surprised you because we’ve known our good old pal to be yellow for a long time. However, ex-NASA astronaut Scott Kelly shared a space fact on Twitter and stated that he can confirm that the Sun is white and not yellow.
The Sun is White But Appears Yellow
The Sun appears yellow to us on Earth because our atmosphere scatters light from the Sun, causing the apparent colour of the sun to change. This same scattering effect is responsible for why the sky appears blue during the day rather than black at night.
What is happening here is that the Earth’s atmosphere scatters light in the blue and violet wavelength ranges, making the remaining wavelengths appear yellow. This is why the sky often appears yellow as the Sun disappears over the horizon, and why the sky/Sun can appear more red at times during this phase of the day.
As the sun sets, more of the shorter wavelength blue is scattered due to the sun’s decreased angle relative to you; thus, the light must pass through more atmosphere to reach you. Because of the increased diffusion, less of the blue wavelength is visible to you, and what remains appears yellow. Similarly, if the air is dusty or contains a lot of larger particles, this will filter out longer wavelengths, resulting in a red sky and red sun.
Why Do Pictures of the Sun Look Yellow?
When you look at a NASA photo of the sun or a photo taken through a telescope, you’re usually looking at a false colour image. Yellow is frequently chosen as the colour for the image because it is familiar. Photos taken with green filters are sometimes left unprocessed because the human eye is most sensitive to green light and can easily distinguish detail.
According to NASA:
During extremely hot, explosive, high-energy solar flare events, the sun also emits massive amounts of x-ray and gamma-ray radiation, reaching over 100 MeV energies and 1032 ergs of energy in a matter of seconds or tens of seconds! Massive solar flares are massive explosions in the sun’s atmosphere caused by the sudden release of magnetic field energy, and they typically occur near solar maximum. Flares also cause charged particle plasmas to accelerate to high speeds, resulting in radio emissions. As a result, the sun emits energy at all wavelengths, from radio to gamma rays. However, as seen in the image above, it emits the majority of its energy at 500 nm, which is close to blue-green light. So one might say that the sun is blue-green!
But this is physics, not psychology. Another spectral signature from the sun, the photon flux, should be mentioned here. When we use Max Planck’s relationship, E = hf (that is, Energy = the Planck Constant times the Frequency), to convert solar irradiance into photon counts, the spectral signature across visible wavelengths is much flatter, and the sun is perceived as more yellow.
Did you ever think that the Sun is white and not yellow? Did this thought ever cross your mind?
Also, Read: Modern Technology is Akin to the Metaphysics of Vedanta
