Is our sun really white, not yellow?

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A popular tweet about the sun’s true color has sparked a debate on Twitter as users debate whether our nearest star is really white or yellow.

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On September 12, the Latest In Space Twitter account, which tweets space-related news and facts, tweeted: “Space Fact: The sun is actually white, but appears yellow because of Earth’s atmosphere.”

Within 24 hours, the tweet had gained over 1,000 retweets and just under 10,000 likes, as well as hundreds of replies.

“Not white!” wrote a user who pointed to distinctly yellow images of the sun posted on the NASA website.

“So why is it classed as a ‘Yellow Dwarf’ star?” asked another.

An illustration of a sunset over water. Sunsets appear red, orange, or yellow because the atmosphere scatters sunlight.
Magann/Getty

Facts

Color is subjective. The way human eyes have evolved to see color means that humans see things that might appear to be a completely different color to an animal, whose eyes are configured differently.

It is also true that some colors of sunlight are more energetic than others. Most of the energy emitted by the sun is in the part of the light spectrum that we perceive as greenfor example.

But speaking only of how humans view the sun, it would be accurate to say that the color of the sun is indeed white.

It may be natural to say that the sun is yellow because some of its most striking appearances in everyday life are when it turns the whole sky orange or red at sunset or sunrise. However, it is not because the sun only illuminates us in yellow.

The reason sunsets and sunrises appear red, yellow, or orange because when the sun is lower in the sky, its light must pass through more of the earth’s atmosphere to reach the ground than when the sun is directly above.

The longer it takes for sunlight to pass through the atmosphere, the more shorter wavelengths of light, such as blue, will scatter, while longer wavelengths, i.e. red, can continue for much longer distances. So the reason sunsets and sunrises appear red is that we have more red light left to see by the time the sunlight reaches our eyes. The same effect also causes red moons.

Apart from the scattering influence of our atmosphere, astronauts agree that sunlight appears white. “I can confirm this space fact,” tweeted former NASA astronaut and International Space Station Commander Scott Kelly in response to Latest In Space’s tweet claiming the sun was white.

The reason sunlight in space appears white to human eyes is that the intense light emitted by the sun is “essentially all colors mixed together”, according to the Stanford Solar Center at Stanford University.

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A NASA photo taken during a spacewalk shows bright white light seen from the International Space Station (ISS) in July 2020. Sunlight appears white in space due to the absence of Earth’s atmosphere.
Nasa

When all the colors are mixed, they appear white to human eyes. The proof that sunlight is made up of many different colors of light mixed together can be found in rainbows. Rainbows are basically sunlight that has been split into its component parts by passing through raindrops. A similar effect can be achieved with a prism.

The reason images of the sun appear yellow or even green or blue in some NASA images is that they have been modified or filtered that way to show certain detail. The sun is indeed classified as yellow dwarf star, but that’s a misnomer – it doesn’t mean that the sun looks yellow to us. The name simply refers to the average size of the sun, common to this class of stars.

decision

True

True.

Seen from the perspective of a human being and eliminating the scattering effect of the Earth’s atmosphere, sunlight is white. This has been confirmed by astronauts in space and can also be seen in photos of the sun seen from space.

FACT CHECK BY NEWSWEEK

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