High School

Astronomy

Week 2: April 13 - 17

About The Sun

1. The sun is the most important object to us on earth because it provides the energy that allows us to flourish.

2. The sun is an average star. Astronomers often refer to the sun as a "typical star" or an "ordinary star.”

3. It is sunlight bouncing around among air molecules that makes the sky blue.

4. Our sky is so brightened by the sun that other stars are hidden from us in the daytime.

About The Sun

5. The sun is very massive. It is 300,000 times as massive as the earth, and 1,000 times as massive as Jupiter.

• The ratio of the mass of the sun to the mass of the earth is about the same as that of three 220-pound NFL linebackers relative to the mass of a paperclip.

6. By studying the sun, we learn about the properties and processes of distant stars.

7. About 93% of the sun is hydrogen, 6% is helium, and in the remaining 1% is found a mixture of all of the other elements.

Parts Of The Sun

The sun has three basic regions: the core, the inner zones, and the atmosphere.

Parts Of The Sun: The Core

• Found at the very center of the sun
• 10% of the sun's diameter
• 15,000,000 degrees Celsius
• Made entirely of gas
• Has a density of 10 times greater than iron
• Heat and pressure strip electrons from their nuclei
• Hydrogen is being fused into helium
• Other fusion reactions are also taking place in the sun

Parts Of The Sun: Inner Zones

• Radiative zone
• The zone surrounding the core
• Abouf 2,500,000 degrees Celsius
• Energy moves out from atom to atom in a series of electromagnetic waves
• Convective zone
• Around the radiative zone
• About 1,000,000 degrees Celsius
• Energy moves by convection
• Warm (less dense) matter rises, cooled (more dense) matter sinks

Parts Of The Sun: The Atmosphere

• Surrounds the convective zone
• Made of three layers:
• Photosphere
• Chromosphere
• Corona

Parts Of The Sun: The Atmosphere

• Photosphere
• Innermost layer of the atmosphere
• Means light sphere
• Made of bubbling gases
• 6,000 degrees Celsius
• Has grainy appearance (granulation)
• The radiation is visible – we consider this to be the “surface of the sun” because it is the photosphere layer we see when we look up ot the sun

Parts Of The Sun: The Atmosphere

• Chromosphere
• Middle layer of the atmosphere
• Means color sphere
• Glows with reddish light
• 4,000 to 50,000 degrees Celsius
• Can create narrow jets of hot gas

Parts Of The Sun: The Atmosphere

• Corona
• Means crown
• Outermost layer of the sun
• Relatively thin layer of heated gases
• Prevents atomic particles from the sun from escaping into space – however, there are holes in the corona through which some particles do escape causing solar wind

Hydrogen Fusion (Nuclear Fusion)

The nuclei of hydrogen atoms are the primary elements in the fusion occurring in the sun. The sun contains a greater amount of hydrogen atoms than it does any other kind of atom.

Hydrogen is the simplest of all of the atoms. It consists of one electron and one proton. In the sun's core, most of the hydrogen atoms have lost their electrons due to the great heat and pressure. They are simply protons.

Nuclear Fusion

Nuclear fusion produces most of the sun’s energy and consists of 5 steps:

1. Two hydrogen nuclei (protons) collide and fuse.
2. One of these protons changes into a neutron.
3. Another proton combines with the proton-neutron pair, producing a nucleus made up of two protons and one neutron.
4. Two of these nuclei collide and fuse.
5. The resulting cluster throws off two protons. The remaining combination of two protons and two neutrons is the nucleus of the helium atom.

Fusion Reaction In The Sun

Riddle

Why did the sun go to school?

Answer

To get brighter!