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).

Stars

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

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

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

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)

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