On the morning of September 28, skygazers across Britain were shocked when they looked up to discover that the Sun had turned blue.
Unusual Shade of the Sun
Images of this bizarre event have flooded X (formerly Twitter), where several confused users discussed this phenomenon. According to experts, the unusual shade is not anything to worry about, and there is a simple explanation behind this.
As Meteorological Office deputy chief forecaster Dan Harris explained, this air currently contains smoke from Canadian wildfires. When smoke is combined with high clouds in the atmosphere, it can scatter sunlight and create unusual color shifts.
In response to threads about the blue Sun, ITV's weather presenter Chris Page explained what was happening. According to Page, the sunlight was diffused by wildfire smoke which has been pulled from North America due to Storm Agnes.
As NASA explains, each visible color has a different wavelength. Violet contains the shortest wavelength at around 380 nanometers while red has the longest wavelength at around 700 nanometers. As sunlight travels towards the Earth, it naturally scatters through particles in the air such as dust and smoke. The shorter the wavelengths, the easier it is for sunlight to be scattered. This phenomenon explains why the sky is blue.
With more smoke in the atmosphere, as is the case brought by the wildfires in Canada, it allows more scattering and even makes the Sun appear blue.
This is not the first time that such a bizarre event has happened. In 1950, people across the cities and towns in Ontario witnessed that the Sun had appeared. This event was due to the Chinchaga firestorm which is considered as one of the biggest wildfires on record in North America.
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What Is the True Color of the Sun?
Young children and even adults usually illustrate the Sun as having yellow or orange color, but experts suggest that it is not actually its true color. The colors of the stars depend on their surface temperature and on the wavelength of light that the human eye can perceive.
The Sun emits light over a whole range of wavelengths. In fact, it emits radiation from all regions of the electromagnetic spectrum, apart from gamma rays. The peak in its spectrum can be used in determining its surface temperature, which is about 9,944 degrees Fahrenheit (5,780 Kelvin).
The peak wavelength in a spectrum also determines the apparent color of an object. Cooler stars appear red while hotter stars appear blue, with orange, yellow, and white stars in between. For the Sun, the spectrum peaks at a wavelength that would be described as green.
Across the narrow range of the visible spectrum, however, the amount of light emitted at each wavelength is almost exactly the same. The human eye does not perceive light by averaging the different colors of the spectrum together, so a very slight excess of green light does not look green to the human but appears white instead. The Sun needs to emit green light only for the human eye to perceive it as green.
If the actual color of the Sun is white, then why does it generally look yellow? This is because the Earth's atmosphere scatters blue light more efficiently than red light. The slight deficit in blue light means that the human eye perceives the color of the Sun as yellow.
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