The Sun
The Sun is the center of our solar system. It is located in the Milky Way, and was born in Nebula. The majority of scientists believe that the Sun was formed approximately 4.6 billion years ago.
The Sun is composed mostly of hydrogen gas. The Sun also consists of other substances. The atmosphere is made up of 75% Hydrogen gas, and 25% Helium gas. It has many different layers; the surface is called the photosphere and the atmosphere is called the Corona. The Corona is shaped like an irregular halo. The Corona is approximately 2.2 million degrees Celsius. It can be visible from earth during an eclipse. The estimated surface temperature of the Sun is 5,500 degrees Celsius.
The Sun is approximately 149 million km away from the earth. There is no solid surface on the Sun. The Suns core is approximately 400 000 km in diameter. The temperature of the suns core is about 15.5 million degrees Celsius. The planet that is located closest to the sun would be Mercury, it is the smallest planet and it is hot enough to melt lead. There is no air on Mercury, and it is covered with craters. The sun is 1.4 million km in diameter, which is 109 times wider than the earth. The planet located farthest from the Sun would be Neptune. It is the coldest planet in our solar system having an average surface temperature of -220 degrees Celsius.
When measuring the distance between the Sun and other planets, the unit of measurement used is the astronomical unit. One astronomical unit is equal to the distance from the Sun to the Earth which is 149 599 000 km. The reason astronomical units were created, is because it is much simpler to express the distance between the Sun and a planet using a unit of measurement that measures a greater amount of space without using as many numbers. For example when measuring the distance from the Sun to Mars, it would be 1.5 AU which is almost 228 000 000 km.
Key Terms form Sun Section (pg 443-445)
Solar prominences
A large eruption of glowing gas that starts on the Sun and rises high above it.
Sun spots
A region on the Sun that is cooler and there for looks darker than its surroundings.
Solar flares
Near sun spots a high temperature eruption of gases on the Sun; they usually cause radio and magnetic disturbances on Earth.
Solar wind
Streams of electrically charged protons and electrons discharged by the Sun, often associated with sun spots and solar flares.
Photosphere
Around the Sun, the region from which the Sun's light originates.
Corona
An irregularly shaped halo around the Sun
Inner planets
Mercury, Venus, Earth, Mars
Outer planets
Jupiter, Saturn, Uranus, Neptune