* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download CH27.2 Stellar Evolution
Survey
Document related concepts
Observational astronomy wikipedia , lookup
Cassiopeia (constellation) wikipedia , lookup
Nebular hypothesis wikipedia , lookup
Corona Australis wikipedia , lookup
Spitzer Space Telescope wikipedia , lookup
History of supernova observation wikipedia , lookup
Stellar kinematics wikipedia , lookup
Perseus (constellation) wikipedia , lookup
Astronomical spectroscopy wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Star of Bethlehem wikipedia , lookup
Dyson sphere wikipedia , lookup
Cygnus (constellation) wikipedia , lookup
Crab Nebula wikipedia , lookup
H II region wikipedia , lookup
Corvus (constellation) wikipedia , lookup
Star formation wikipedia , lookup
Transcript
Date:_____________ Topic:____________ Stellar Evolution CH 27 Section 2 A typical star exists for billions of years, making it impossible for astronomers to study a single star through it’s entire life. Astronomers developed Theories –scientifically acceptable explanations for observed facts. Through the years, scientists have developed a theory on the life of stars……starting with A…… N E B U L A NEBULA – birthplace of a star, about 70% hydrogen, 28% helium and 2% “heavier elements” The process of a star’s “birth” is thought to begin with the explosion of a nearby star, causing a sphere of matter to build at the center of the nebula. As gravitational forces increase, the nebula becomes smaller and spins faster. Protostar – 2nd step in the evolution of a star. The center of a shrinking, spinning nebula. Temperature begins to increase at the center, due to: 1. The collision of particles. 2. Increased pressure. At a temperature of 10,000,000 degrees Celsius NUCLEAR FUSION begins and the PROTOSTAR begins to generate energy. THEN it is considered to be a star. A nebula may produce more than one star………….. and is thought to be where planets develop, revolving around a central star. MAIN SEQUENCE STARS – Longest stage in the life of a star. MUCH ENERGY IS GENERATED IN THIS PHASE The process of FUSION releases enormous amounts of energy! When 1 gram of Hydrogen is converted into Helium, enough energy is released to light a 100 watt light-bulb for 3,000 years. 10 times the size of the sun Giants and 100 times the size Supergiants of the sun -3rd stage of a star - when almost all the hydrogen has been fused to helium. The core of the star contracts causing higher temperatures and the helium to be fused into carbon atoms. White Dwarf stars – the end of helium fusion A hot dense core is all that remains and can “shine” for billions of years before completely cooling. -the core heats and illuminates(lights) the remaining gases - these gases appear as a PLANETARY NEBULA Black Dwarf - when a white dwarf no longer emits energy - “dead star” NONE are yet known to exist…..our universe isn’t thought to be old enough for this to happen yet! NOVA Not all white dwarfs just cool and die. Some may have one or more large explosions, causing them to become very bright for a short time(days) -explosive release of energy, gas and dust into space SUPERNOVA -when a large star(10-100 times the size of the sun) has such a large explosion that it blows itself up. The largest known release of energy in the universe. Can be seen for weeks. In 1054 Chinese astronomers saw an explosion that was so bright it could be seen during the day for three weeks! Neutron Star -incredibly dense ball of neutrons left over after a supernova explosion - some emit(give off) two beams that sweep across space –called PULSARS Black Holes -leftovers from some massive stars -extreme gravity – keeps light from escaping VERY difficult to detect(see). Today black holes are thought to be at the cores of many galaxies.