The Sun: Our Very Own Star

1. The Sun: Our Very Own Star Pgs. 43 - 48

2. Structure of the Sun Although the sun looks like is has a solid surface it is actually composed of several layers. The corona is the sun’s outer atmosphere. It is only visible during a solar eclipse. The chromosphere is a thin layer (300okm). It is only seen during a solar eclipse as well. The photosphere is where gases are thick enough to see. It is the visible surface layer of the sun 600km thick.

3. Structure of Sun continued The convective zone is a region about 200,000km thick where gases circulate in convection currents. Hot gases rise and cooler ones sink. Radiative zone is a dense region 300,000km thick, where the atoms are so closely packed that light can take millions of years to pass through. The core is at the center of the sun. The core has a radius of 200,000km and produces the sun’s energy. Temperatures can reach near 15,000,000 degrees Celsius.

5. Energy Production in the Sun How long can our sun last? So far the sun has been shining for at least 4.6 billion years. What is allowing the sun to burn for so long? Even though the sun is giving off energy, it is producing energy as well. If it wasn’t the sun would have only lasted about 10,000 years.

6. Burning or Shrinking Scientists have also thought that the sun is slowly shrinking due to gravity. The release of energy due to gravity is powerful but not enough to keep the sun burning this long. The energy released from the sun from gravity would allow it to only last about 45 million years. Something else is occurring to allow the sun to burn this long.

7. Nuclear Fusion In the early 1900’s, Albert Einstein discovered that matter an energy are interchangeable. Matter can be converted to energy as demonstrated by E = mc2 E is energy, m is mass and c is the speed of light. The speed of light is such a large number that any small mass could produce a large amount of energy. Nuclear Fusion is the process by which two or more nuclei with small masses join together to form a larger nucleus. During fusion, energy is produced!

8. Fusion in the Sun Most of the time nuclei of hydrogen atoms do not get close enough to combine. They are positively charged and repel each other like magnets of the same charge. At the center of the sun, the high temperature and pressure force hydrogen nuclei to overcome their repulsion and fuse. The energy produced in the core of the sun takes millions of years to reach the sun’s surface. It must travel through the core to the radiative zone, to the convective zone and to the photosphere before it makes its way to Earth.

9. Hydrogen Fusion

10. Sunspots The circulation of gases within the sun produces magnetic fields that reach out into space. The magnetic fields slow down activity in the convective zone. This causes areas of the photosphere to be cooler than others. These are shown as dark spots call sunspots. The number of sunspots and location are changing in a regular cycle.

12. Solar Flares The same magnetic fields that cause sunspots cause disturbances in the sun’s atmosphere. Giant storms on the surface of the sun called solar flares can have temperatures of over 5 million degrees Celsius. Solar flares send out huge streams of particles from the sun. The particles interact with the Earth’s atmosphere to make fantastic light shows called auroras. Solar flare can interrupt radio signals and satellite signals on Earth.