1. How are stars born, and how do they die?
Today’s Question – 10/29
How are stars born, and how do they die?
(2-3 complete sentences).

2. Stars

3. Stellar Distance Solar System Distances Stellar Distances
Astronomical Unit (au): 93 million km, distance from Sun to Earth
Stellar Distances
Light-year (ly): 9.5 trillion km, the distance light travels in space in one year
Parsec (pc): 30.9 trillion km, 3.26 ly

5. Electromagnetic Spectrum
Radiation heat transfer travels as electromagnetic waves (em waves) through space
Radio waves, infrared waves, optical waves (light), x-rays, gamma rays
All can be measured by telescopes
Can help us discover color, temperature, distance, what objects are made of, and more

7. Star Classification
Stars: Huges spheres of helium and hydrogen gases with nuclear fusion reactions in their cores
Classified by color, temperature, size, composition, and brightness
Cooler stars are reddish, medium stars are yellow, hot stars are blue
O, B, A, F, G, K, M – hottest to coolest
Small stars are dwarf stars, very large stars are giants or super-giants, medium stars are called main-sequence stars

8. Birth of Stars Nebula: cloud of dust and gas, where stars are born
Protostar: a contracting region of dust and gas within a nebula, will probably become a star
Small stars (dwarfs) use their fuel slowly and live a long time (200 billion years, give-or-take)
Large stars use their fuel quickly and live shorter lives (10 billion years, give-or-take)

9. Death of Stars
As stars use up their fuel, their cores shrink and their outer portions enlarge, and they become red giants or red supergiants
When smaller stars “die” they lose their outer layers and become planetary nebulas, and then white dwarfs or black dwarfs
When larger stars “die”, they often explode in supernovas, then form black holes or neutron stars