The Sun, Life Cycle of a Star & HR Diagram Notes 8.8AB

Unlock the secrets of star life cycles and the HR diagram! Explore nebulae, giants, and black holes.

What observations can you make from this picture? The Sun Stars differ in many ways: mass, size, apparent magnitude (brightness), luminosity (absolute brightness), temperature (color), and structure.The Sun is a medium-sized star that exists on the far edge of the spiral-shaped Milky Way GalaxyThe Sun is much closer to the Earth than any other star. It is about 150 million km away from us, which is about eight light minutes away.The next closest star to us is about four light-years away! • The Sun was formed from a large cloud of dust and gas called a nebula. STARS •A huge burning sphere of gases held together by gravity•Composed mainly of the elements Hydrogen and Helium•Life cycle based on their mass•All stars go through the same first 3 life cycle stages 1.Nebula – a huge cloud of dust and gas held together by gravity; star nursery 2.Protostar – a young star in the early stages of formation; nuclear fusion begins (light and heat produced) 3.Main Sequence – 90% of stars are in this stage of their life cycle. NEBULA •A huge cloud of dust and gas in space held together by gravity – referred to as “star nurseries”•Mainly consist of Hydrogen and Helium gas•Can be many light years in diameter•Some are regions where new stars are being formed, while others are the remains of dead or dying stars•Examples of Nebulas – Cat’s Eye Nebula, Eagle Nebula, Crab Nebula LIFE CYCLE - AVERAGE MASS - STARS WITH AN AVERAGE MASS LIKE THE SUN •Red Giant – the stage after main sequence for a small to medium mass star; fuel begins to run out•Planetary Nebula – a ring-shaped nebula formed by an expanding shell of gas around an aging star•White Dwarf – a star that has exhausted all of its nuclear fuel; planet sized and very dense•Black Dwarf – a dead star that no longer gives off light or heat LIFE CYCLE - HIGH MASS - STARS THAT ARE 1.5X-3X MORE MASSIVE THAN THE SUN •Red Supergiant – a star that is among the most massive and brightest of all stars•Supernova – an extremely bright explosion of a star•Neutron Star – the extremely dense remains of a dead star; very small and very dense LIFE CYCLE - EXTREMELY HIGH MASS - STARS MORE THAN 3X MASSIVE AS THE SUN •Red Supergiant•Supernova•Black Hole - a gravitational field so strong that not even light can escape LIFE CYCLE DIAGRAM USE ALL LOWERCASE LETTERS red giant planetary nebula white dwarf black dwarf red supergiant supernova neutron star black hole nebula protostar main sequence Average Mass Star High & Extremely High Mass Star A star's life cycle is determined by its mass! HR Diagram •The temperature of a star is observed in its color.A very hot star appears to be bluein color, and a very cool star appears red.•The Hertzsprung-Russell diagram compares the luminosity and temperature of stars. It is used as a tool to classifystars.•A chart that graphs a star’s brightnessand temperature•Temperature increases as you move toward the left side of the chart•Brightness increases as you move toward the top of the graph•The category or type of star is generally included – Main Sequence, Supergiant, Giant, White Dwarf•The color of stars can also be represented (from hottest to coolest) – Blue, White, Yellow, Red-Orange, Red MAIN SEQUENCE •90%of known stars are in the main sequence stage of their life cycle•The Sun isa yellow main sequence star with an averagetemperature and brightness•Main sequence stars can range from hotand bright(top – left) to cooland dim(bottom – right) GIANTS •The stage after main sequence for a smallto mediummass star; fuelbegins to run out•Arcturusis a red-orange giant star that is brighter, but cooler than the Sun•Giant stars are typically cooler stars that are averagein temperature SUPERGIANTS •The stage after main sequence for a high mass star•Deneb is a white supergiant star that is brighter and hotter than the Sun•Supergiant stars are extremely bright and can range from hot to cool WHITE DWARFS •Formed when a low-mass star has exhausted all its nuclear fuel and lost its outer layers•Sirius B is a white star that is much more dim, but hotter than the Sun•White dwarf stars are extremely dim and typically average to hot in temperature