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Until about 4.6 billion years ago, our solar system was a giant cloud. It was made up of gas, dust, and ice. As the cloud whirled around, gravity caused it to shrink. The inner part became the Sun. The outer pieces took shape as the planets.
The Sun formed because heat and pressure within the cloud triggered nuclear fusion. Hydrogen atoms were crushed—or fused—together to form helium atoms. This released huge amounts of energy. The same reaction happens when a hydrogen bomb explodes. Intense gravity keeps these ongoing explosions from ripping the Sun apart.
Core
The Sun’s nuclear core is about the size of Jupiter. However, it’s much denser.
Temperature: 27 million degrees F
Granules
Each line, or squiggle, is about 600 miles across. Granules occur because of the rising and falling of gases. Each one lasts about eight minutes.
Sunspots
As heat rises to the surface, magnetic fields get stirred up. This creates dark patches that are about 2,200 degrees cooler than the surface.
Temperature: 7,800 degrees F
Radiative Zone
Energy here radiates out from the core.
Temperature: 4.5 million degrees F
Photosphere
(sphere of light)
This “surface” layer is 340 miles deep. It’s the part of the Sun we see.
Temperature: 10,000 degrees F
Chromosphere
(sphere of colors)
This part of the Sun’s atmosphere gets its name from the faint reddish light it gives off. Its average thickness is about 6,000 miles.
Temperature: 50,000 degrees F
Solar Wind
This stream of particles flows out from the Sun in all directions. It moves up to 1 million miles per hour! The solar wind is, in essence, the solar corona expanding into space.
Solar Happenings
A lot of solar activity occurs every day. There are eruptions of all sorts: flares, prominences, coronal loops, and coronal mass ejections.
Corona
(halo or crown)
Thin gases make up the outer layer of the Sun’s atmosphere. This is about 1 million miles high. The corona can be seen only during a solar eclipse.
Temperature: 4 million degrees F
Solar Happenings
A lot of solar activity occurs every day. There are all kinds of eruptions: flares, prominences, coronal loops, and coronal mass ejections. What exactly are these things? Read on to find out.
Gallery of Solar Happenings
Flares are sudden, bright outbursts of energy that occur around sunspots as magnetic fields tear and reconnect. One solar flare can release the same energy as 40 billion atomic bombs.
▲ In 1938, scientists Hans Bethe and Charles Critchfield showed why the Sun is so hot and bright. Nuclear fusion in its core turns 700 million tons of hydrogen into helium each second. To do that, the nuclei of four hydrogen atoms must combine into one helium nucleus. This creates heat, light, and radiation. The Sun has enough hydrogen to burn for another 5 billion years.
Sun Facts
Diameter
865,000 miles, or about 109 times larger than Earth
