 The sun is believed to be roughly 4.6 billion years of age.  Early scientist use to believe that the sun generated its energy by burning fuel.  This process could not produce enough energy to power the sun.  The sun would have only lasted for 10,000 years.

 Later scientist thought that gravity was causing the sun to slowly shrink.  They thought that gravity would release enough energy to heat the sun.  If this were to occur the sun would have only lasted for 4.5 million years.

 Albert Einstein showed that matter and energy are interchangeable.  E=mc²  E = energy  m = mass  c = speed of light  Because c is such a large number small amounts of matter could create large amounts of energy.

 Nuclear fusion – the process by which two or more low-mass nuclei join together, or fuse, to form another nucleus.  Example 4 hydrogen nuclei fuse to form a single helium nucleus.

 Hydrogen ions are positive charges that are repelling to each other.  But how do they fuse?

 Temperature and gravity are very high inside the sun resulting in the nuclei overcoming the repulsive forces.  Hydrogen fuses into helium.  Light in the core takes millions of years to reach its surface due to the large amount of energy in the radiative zone.

 Hydrogen Atoms are stripped of their electrons due to the extreme temperatures and pressures in the sun. 1. Due to the exposure of the nucleus when the atoms combine they can exchange the protons left inside. 2. One of the protons changes into a neutron. 3. Another proton combines with the p-n pair producing a nucleus made of 2p and 1n.

4. Two of these nuclei combine and fuse. 5. Two protons are thrown out leaving behind 2p and 2n aka helium.

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 The Sun is responsible for 99% of the solar systems mass.  Large ball of gas made up of mostly hydrogen and helium which is held together by extreme forces of gravity.

 The sun does not have a solid structure.  You actually can see through the outer layer of the sun.  Visible layer is the layer in which the gas becomes so thick that you cannot see through it.

 The splitting of an atom into two parts.  How does this process provide energy?

 Energy is produced when an alpha particle is ejected from the Uranium-235 to split it into two lighter elements.  This occurs naturally.

 Alpha Particle – a particle that consist of 2 protons and 2 neutrons that is ejected during radioactive decay.  nuclear-power-plant-pictures.htm nuclear-power-plant-pictures.htm

 The sequence of (exothermic chemical reactions) heat releasing reactions between a fuel and an oxidant accompanied by the production of heat.  Produces light and heat.  Typical reaction:  CH4 + 2O2 -> CO2 +2H20 + ENERGY

The Atmosphere  “Twinkle, Twinkle Little Star”  Stars don’t “twinkle”- the atmosphere causes starlight to shimmer and blur and look like it’s twinkling  Light gathered by telescopes on the Earth’s surface is affected by the atmosphere  On Earth- top of mountain is good location for telescope because of thinner air  Best place- Space because no atmosphere to interfere with light

 Due to Earth’s atmosphere the following wavelengths of light are blocked:

 Radiation – The form in which energy is released from the Sun and travels through space.

Electromagnetic Spectrum  All of the wavelengths of electromagnetic radiation Invisible Invisible LONG SHORT ROYGBIV Visible portion

 Ultraviolet (UV) wavelengths have the greatest energy out of the energy that reaches Earth’s surface.  Only about 7% of solar radiation is in the UV wavelengths.

 The three types are:  UVC: the highest energy ultraviolet, does not reach the planet’s surface at all.  UVB: the second highest energy, is also mostly stopped in the atmosphere.  UVA: the lowest energy, travels through the atmosphere to the ground.

 The remaining solar radiation is the longest wavelength, infrared.  Most objects radiate infrared energy, which we feel as heat.  Some of the wavelengths of solar radiation traveling through the atmosphere may be lost due to absorption by Earth’s ozone layer, O2, CO2, and H2O.

 The transfer of energy from the Sun across nearly empty space (remember that space is a vacuum) is accomplished by radiation.  Radiation is the transfer of energy by electromagnetic wave motion.

 The unpredictable path a photon takes to get out of the Sun’s radiation zone.  Can take millions of years to escape the Sun due to its density.  Example: Attempting to walk through a crowded subway station blindfolded.