Research questions and inquiry methods

Electromagnetic waves are energy waves produced by the oscillation or acceleration of an electric charge. They include radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays, and gamma rays. Their wavelengths in meters are: radio waves (0.1 to 1000), microwaves (1 x 10-3 ~ 1 x 10-1); infrared (7 x 10-7 ~1 x 10-3); visible light (4 x 10-7 ~ 7 x 10-7); ultraviolet rays (1 x 10-8 ~ 4 x 10-7); x-rays (1 x 10-11 ~ 1 x 10-8) and gamma rays (< 1 x 10-11).

Scientists have inferred that such great amounts of energy as produced by the Sun (4x1026 watts per second) can only be the result of nuclear fusion

If such energy were produced through the most efficient chemical reaction, the Sun would not last for more than a few thousand years. Evidence suggests that the lifespan of the Sun is in billions of years; hence the Sun's energy cannot be the result of chemical reaction.

Nuclear fusion occurs when two positively charged atomic nuclei are fused together. In the Sun hydrogen nuclei ("protons") are fused to form helium in its core. Fusion requires extremely high temperatures and densities to overcome the repulsion between positively charged nuclei. Such conditions are present in the core of the Sun (100 times the density of water on Earth, and temperatures of about 27 million degrees F).

5. The factors that make some stars appear brighter than others are their luminosity (how much energy they give out in a given time) and their distance from us. Obviously the stars nearer in distance appear brighter if their luminosity is the same. The luminosity of the stars, in turn, depends on their size, mass, and temperature; hence larger stars may appear brighter than smaller stars although they may be further away.

6. The Sun is an "average" star in terms of its mass, light production, and size. It appears so different from other stars because of its relative proximity to the Earth. All stars including the Sun are balls of hot, glowing gas that are hot and dense enough to trigger nuclear reactions. Most stars have masses between 0.3 to 3.0 times the mass of the Sun.

8. Stars begin to die when they run out of hydrogen. High mass stars, although containing more hydrogen, have a shorter life span than low mass stars. This is because high mass stars have the required conditions in their core (higher pressures and temperatures) for quicker conversion of hydrogen atoms into helium.

9. As the Sun runs out of its hydrogen (an estimated 7 billion years from now) it will balloon into a red giant star engulfing its nearest planet Mercury; will begin to collapse, eventually becoming a small, dense, cool star called a "white dwarf." Much before dying of cold, life on earth would perish from heat as the Sun would be 2000 times brighter than at present at the time it runs out of hydrogen.

10. Low mass (and medium mass) stars eventually become "white dwarfs" when they die. High mass stars explode in supernovae events when they cease to generate fusion energy in its core and collapse inward. The Sun will eventually become a white dwarf as it is categorized as a low mass star.

11. The Solar System, containing the Sun, its nine planets, their moons, asteroids and comets is a small part of the Milky Way Galaxy

located in its outer region known as the Onion Arm. The Galaxy is spiral shaped and about 100,000 light years across while the Solar system is much smaller. The age of the Milky Way is 15 billion years compared with 4.5 billion years of the Solar System.