What Is the Actual Color of the Sun
As we all know, sun is the big ball of heat and light. Sun is the star at the center of the Solar System and it iportant sous the most imrce of energy for life on Earth. Even though the Sun is just right up there, but we still couldn't tell what is the real color of the Sun. To learn further about the color, first let`s get to know what Sun really is.
• What is Sun?
The sun lies at the heart of the solar system, where it is by far the largest object. It holds 99.8 percent of the solar system's mass and is roughly 109 times the diameter of the Earth. So that is about one million Earths could fit inside the sun.
The visible part of the sun is about 5,500 degrees Celsius, while temperatures in the core reach more than 15 million degrees Celsius! According to NASA, to match the energy produced by the sun, you have to explode 100 billion tons of dynamite in every second.
There are more than 100 billion stars in our galaxy.
The Sun is relatively young and known as Population I. Meanwhile, the older generation of stars are known as Population II. There are also the earlier generation that are called Population III, but the members of this generation are still under discovery.
As mentioned above, our Sun is still considered as young even thought it was born 4.6 billion years ago. The sun and its atmosphere are divided into several zones and layers. The solar interior, from the inside out, is made up of the core, radiative zone and the convective zone.
The core extends from the sun's center to about a quarter of the way to its surface. Although it only makes up roughly 2 percent of the sun's volume, it is almost 15 times the density of lead and holds nearly half of the sun's mass.
Next is the radiative zone, which extends from the core to 70 percent of the way to the sun's surface. This has make up 32 percent of the sun's volume and 48 percent of its mass. Light from the core gets scattered in this zone, so that a single photon often may take a million years to pass through.
The convection zone reaches up to the sun's surface, and makes up 66 percent of the sun's volume but only a little more than 2 percent of its mass. Roiling "convection cells" of gas dominate this zone. Two main kinds of solar convection cells exist.
They are granulation cells about 600 miles (1,000 kilometers) wide and supergranulation cells about 20,000 miles (30,000 km) in diameter. The photosphere is the lowest layer of the sun's atmosphere, and emits the light we see. It is about 300 miles (500 km) thick, although most of the light comes from its lowest third.
Temperatures in the photosphere range from 6,125 degrees Celsius at bottom to 4,125 degrees Celsius at top. Next up is the chromosphere, which is hotter, up to 19,725 degrees Celsius. It is apparently made up entirely of spiky structures known as spicules typically about 1,000 km across and up to 10,000 km high.
After that, is the transition region a few hundred to a few thousand kilometres thick. This is heated by the corona above it and sheds most of its light as ultraviolet rays. At the top is the super-hot corona, which is made of structures such as loops and streams of ionized gas.
The corona generally ranges from 500,000 degrees Celsius to 6 million degrees Celsius and can even reach tens of millions of degrees when a solar flare occurs. Light as ultraviolet rays playing an important role in determine what color of rays that the sun actually has.
• What is the Color of the Sun
If we look at most of child drawings, you'll see the sun depicted as a yellow ball. Even many adults associate the color yellow with the sun. But the Sun isn't actually yellow. It's just an illusion caused by the Earth's atmosphere.
So what are the real color of the sun? It is said that the color appear different if you look at the sun from earth and from the space. What has made it different is the atmosphere.
On Earth, the atmosphere filters much of the 'cool' light spectrum, leaving the 'warmer' colors visible to us instead. The filtered blue light refracts from atmospheric molecules, causing the blue appearance of our sky.
The powerful processes happening inside the Sun are so robust that it emits every color of light imaginable. Together, these colors form a pure white light, which is precisely what you'd see from space.
Therefore, the color of the sun is white. The sun emits all colors of the rainbow more or less evenly and in physics, we call this combination "white". That is why we can see so many different colors in the natural world under the illumination of sunlight.
If sunlight were purely green, then everything outside would look green or dark. We can see the redness of a rose and the blueness of a butterfly's wing under sunlight because sunlight contains red and blue light.
The same goes for all other colors. When an engineer designs a bulb that is supposed to mimic the sun, and therefore provide natural illumination, he designs a white bulb, not a yellow bulb. The fact that you see all the fundamental colors present in a rainbow and no colors are missing is direct evidence that sunlight is white.
The sun emits all colors of visible light, and in fact emits all frequencies of electromagnetic waves except gamma rays. This includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, and X-rays. The sun emits all these colors because it is a thermal body and emits light through the process of thermal radiation.
Just like a hot coal or an electric stove element that glows, the sun glows in all colors because of its temperature. That is why incandescent light bulbs emit light that mimics sunlight so well. They contain metal filaments that are heated until they glow in the same way the sun does.
It may be tempting to examine the color content of sunlight and identify the brightest color as the actual color of the sun. The problem with this approach is that peak frequency does not have a concrete meaning.
The peak frequency is different depending on whether you are in frequency space or in wavelength space, as shown in the images below. In wavelength space, sunlight peaks in the violet. In frequency space, sunlight peaks in the infrared. Which is right? They are both right.
They are just two different but perfectly valid ways of measuring color content. According to the wavelength-space blackbody model, the sun peaks in the green! When astronomers say the sun is green, they mean that their inexact model peaks in wavelength in the green.
Note that the plots show sunlight as it is measured in space before entering earth's atmosphere. Data taken from the ASTM Terrestrial Reference Spectra. This is the true color content of the sun. The sunlight that we experience on the surface of earth has been filtered by the atmosphere and is slightly different.
The atmosphere tends to scatter out blue and violet more than the other colors. As a result, direct sunlight on the surface of the earth is slightly redder than sunlight in space. Around sunrise and sunset, when the sunlight travels through a lot more atmosphere than usual, sunlight on earth's surface becomes even more red. But the sun itself is white.
• Why sun appear orange and red during sunrise and sunset?
The red colour in the sky at sunset and sunrise is due to an effect called Rayleigh scattering. There is a similar form of scattering called Mie scattering which is responsible for the white colour of clouds.
Particles in our atmosphere that are approximately the same size as the wavelength of visible light cause the white light from the sun to scatter and split into individual components.
Oxygen and Nitrogen (the main components of our atmosphere) scatter violet and blue light due to their small size. This is why the sky appears to be blue in the day time, especially at midday when the Sun is closest to us.
During sunrise and sunset the distance that the light has to travel from the Sun to an observer is at its greatest. This means a large amount of blue and violet light has been scattered. Therefore, the light that is received by an observer is mostly of a longer wavelength and therefore appears to be red.
So we have discovered that the origin color of sun is actually white. But because of the science behind the rays, we are able to enjoy different colors of sun at different angle and reflections.
References:
- Standard Tables for Reference Solar Spectral Irradiances: Direct Normal and Hemispherical on 37° Tilted Surface
- Earth's Sun: Facts About the Sun's Age, Size and History
- Longman Science Physics: Scattering of Light
- Why is the Sky Blue?
- NASA
What Is the Actual Color of the Sun
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