The Sun

The Sun is the closest star to Earth. By studying it, we can learn about other stars in the Universe. Like any other star, the Sun is a luminous ball of hot gas, mostly hydrogen, but some helium, with tiny amounts of other elements. Inside the sun a process called nuclear fusion takes place. What happens is it continually generates energy such as light and heat; at its center, the temperature is around 25,000,000�F (14,000,000�C). The sun was born from a cloud of gas and dust about 5,000 million years ago. It was created in a group of stars that slowly broke up, so that now the Sun is alone. It is the only star known to have a system of planets. But no one of these planets, the Earth, the Sun is not just any old star; it is a provider of energy for life.
The sun is made up of many different layers of gas. The surface layer we see is called the photosphere. Here, the gas swirls and bubbles about, giving the Sun a splotchy look. Surrounding the photosphere is an unseen layer of gas called the corona the corona (which means "crown").
On close inspections, the Sun's photosphere is at times riddled with dark patches. These are sunspots- patches of gas that look darker because they are cooler. Sunspots are caused by magnetic fields that slow down the flow of heat from the Sun's center. They have a dark central region called the umbra, surrounded by a lighter region called a penumbra. They generally occur in pairs of groups.
Today it is only the visible light given out by the sun that can be recorded. Astronomers have special equipment that can take photographs of other wavelengths, such as ultraviolet or infrared. These show up details that normal photographs cannot reveal.
Astronomers use special instruments based on Earth, and other up in space, to study the Sun. The Sun's light is collected through and instrument called a spectroscope. What it does is it splits the Sun light into spectrum (the different wavelengths of light it emits). Astronomers have gained most of their knowledge about the Sun by studying its spectrum.



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