Sun- The Undefined

The birth of 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 The visible part of the sun is about 10,000 degrees Fahrenheit (5,500 degrees Celsius), while temperatures in the core reach more than 27 million F (15 million C), driven by nuclear reactions. One would need to explode to match the energy produced by the sun, according to NASA.

The sun is one of . It orbits some 25,000 light-years from the galactic core, completing a revolution once every 250 million years or so. The sun is relatively young, part of a generation of stars known as Population I, which are relatively rich in elements heavier than helium. An older generation of stars is called Population II, and an earlier generation of Population III may have existed, although no members of this generation are known yet.

Magnetic Field of Sun

The strength of the sun's magnetic field is typically only about twice as strong as Earth's field. However, it becomes highly concentrated in small areas, reaching up to 3,000 times stronger than usual. These in the magnetic field develop because the sun spins more rapidly at the equator than at the higher latitudes and because the inner parts of the sun rotate more quickly than the surface. These distortions create features ranging from sunspots to spectacular eruptions known as and coronal mass ejections. Flares are the most violent eruptions in the solar system, while are less violent but involve extraordinary amounts of matter — a single ejection can spout roughly 20 billion tons (18 billion metric tons) of matter into space.

Chemical Composition

Just like most other stars, the sun is made up mostly of hydrogen, followed by helium. Nearly all the remaining matter consists of seven other elements — oxygen, carbon, neon, nitrogen, magnesium, iron and silicon. For every 1 million atoms of hydrogen in the sun, there are 98,000 of helium, 850 of oxygen, 360 of carbon, 120 of neon, 110 of nitrogen, 40 of magnesium, 35 of iron and 35 of silicon. Still, hydrogen is the lightest of all elements, so it only accounts for roughly 72 percent of the sun's mass, while helium makes up about 26 percent

Nuclear fusion in the core

At the core of , gravitational attraction produces immense pressure and temperature, which can reach more than 27 million degrees Fahrenheit (15 million degrees Celsius). Hydrogen atoms get compressed and fuse together, creating helium. This process is called .

Nuclear fusion produces huge amounts of energy. The energy radiates outward to the sun's surface, atmosphere and beyond. From the core, energy moves to the radioactive zone, where it bounces around for up to 1 million years before moving up to the convective zone, the upper layer of the sun's interior. The temperature here drops below 3.5 million degrees F (2 million degrees C). Large bubbles of hot plasma form a soup of ionized atoms and move upward to the photosphere.

What is the colour of Sun?

The Sun emits a lot of energy in the visible range. In wavelength scale it is from 390 nm to 700 nm, and when you translate it to colors, you get all colors from violet to red, just as we see them in the rainbow. When you mix all those colors together you get white, and that is why white is the true color of the Sun. Check out photos of the Sun taken by astronauts (with no filters). The Sun appears white on them!

But seen from the Earth, the Sun can have many colors: from whitish-yellowish when it is high above the horizon, to red when it sets or rises. But you are right - most people see it as yellow, because the shortest wavelengths (that we see as different shades of blue) are being scattered by the Earth's atmosphere, coloring the sky blue. And when our eyes combine all those rainbow colors, except the blue ones, the Sun's color our eyes see is yellowish. The lower toward horizon the Sun is, the more blue is scattered and the "average" Sun's color shifts to red.

The position of star on the H-R Diagram depends on star's temperature and brightness. One of versions of H-R diagram is often called "color-magnitude diagram", but here "color" (or "color index") is a number representing a difference in stellar brightness in two chosen spectral ranges.

In many H-R Diagrams stars are colored according to theirs temperatures (blue for hot stars, red for cool ones) to make them more informative and appealing. The Sun and stars with similar temperatures are yellow when observed from the Earth, and that is why they are often represented with this color and called "yellow dwarfs". However, you can also find diagrams for which real stellar colors are kept and in those diagrams Sun will be a white point.

In some H-R Diagrams colors are coded with the wavelength for which star emits the most of its energy. When we use this criterion, we should use green for the Sun. But why don't we see green stars (from Earth or space)? It is because stars emit energy in a really wide range. Even if the peak falls in green, a lot of energy is emitted in all colors, from blue to red. And with our eyes, we always observe the mixture of those colors. If you add a bit of blue to green, you will get something our eyes interpret as a tint of blue, and when you add something from the red side - you get yellow.