Stars are self-luminous objects shining from energy sources within themselves. By contrast planets shine by reflected light.
By all measure our star, the sun, is a typical star. It has a mass more than 3x10 times that of the earth, 1.99x10 kg, a radius of 696,000 km (about 432,200 mi.) and a power output of
3.8x10 x 10 erg. For comparison purposes, these quantities masses, radius and luminosity are usually
expressed in terms of the Sun.
One of the best known facts about our Sun is its distance, 93 million miles. This is called an (au) astronomical unit. I will have students use the pie method to compare the length of time to arrive at the sun from earth traveling at a speed of a) A plane traveling at 500 mph b) A car traveling at 55 mph c) Walking at a speed of 5 mph.
Some of the lesser known facts are the following: Sunlight has weight! If a square mile of sunlight could be held in your hand it would weigh 3 lbs. All the sunlight falling on the Earth's surface weighs about 87,700 tons. Although this weight is equivalent to the weight of an ocean liner, it is negligible when compared to the Earth's weight.
98.98% of all energy passing through the atmosphere originates in the Sun's core. The light from a chunk of burning coal is really sunlight. Leaves on ancient trees collected sunlight. The ancient trees over time became coal. It is the combustion of coal that liberates the hibernating heat.
The sun is made up approximately 78.4% hydrogen, 19.8% helium and 2% heavy metal such as nickel and iron.
The temperature of the sun at the core is 29x10 Fahrenheit. Under the right pressure the basic fusion reaction is 4 hydrogen atoms fusing into 1 helium atom, and releasing energy (E= m c^2)
Because of tremendous temperature and pressures on the Sun no one from earth could visit it. If an imaginary journey could take place, to leave the Sun, because of it's great mass, an escape velocity of 1.4x10 mph would have to be reached!