The Sun Physical Geography 10
A Star!!! • The sun is the closest star to Earth!!! • 147,166,462 km to 152,171,552 km away from Earth (depending on Earth’s position on it’s elliptical orbit/ revolution around the sun)
The Next Closest Stars To Earth Are: • Proxima Centauri (4.2 light years away) • Rigil Kentaurus/ Alpha Centauri (4.3 light years away)
What is a star? http://www.youtube.com/watch?v=QZDk1cbKp7s&feature=related
Stars • Most stars are made of a gas-like substance called plasma. • Some stars are made of tiny (subatomic) particles that can be packed extremely close together making them very dense.
A Star is Born • Stars are born out of a mass of clouds and gas called a nebula. • Protostar: - Gravity causes the hydrogen gas in the nebula to spin, become hotter, & glow (these are protostars). - Small protostars don’t create enough heat to shine & aren’t classified as real stars. - Medium & large protostars spin until they reach extremely hot temperatures. This causes nuclear fision to occur (the hydrogen in the stars turns into helium) producing a significant amount of heat and light.
Color & Heat • The color of the star has to do with the star’s surface heat. • Stars with the hottest temperatures are blue • Stars that are least hot are red • Our sun falls in between the hottest and coolest (it glows yellow)
Death of a Star • Stars die when they run low on hydrogen and can no longer sustain nuclear fusion (turn hydrogen into helium). • As stars’ fires begin to cool & die they generally turn red.
Our Sun Has A: • circumference (distance around) 100 x greater than Earth’s • mass 3000000 x greater than Earth • gravitational pull that rules the planets, satellites, and other forms of space junk • core temperature of 14000000 degrees Celsius
The Sun • Revolves around the galactic center (at a velocity of 800 000 km/h) completing a revolution every 250 million years • Gives off radiation (only a small portion reaches earth) • Produces enough heat and light to support plant and animal life on Earth (other planets receive too little or too much energy to support life)
What is a Solar Eclipse? • The moon passes between the Sun & the Earth, blocking most of the sun’s light from the earth. • When this occurs you can see a ring of light around the moon (part of the sun the moon didn’t cover). • They occur in cycles & there are approx. 18 years between eclipses of the same kind