Life Cycle of Stars 2005 K.Corbett

3 categories of stars Sun-sized stars (up to 6 times the size of the sun) Huge stars (6 - 30 times the size of the sun) Giant Stars (over 30 times the size of the sun) 2005 K.Corbett

The life of Sun-sized stars Born in a nebula (a cloud of gas and dust, mostly Hydrogen). The star produces energy from nuclear fusion of Hydrogen into Helium. This type of star lasts for about 10 billion years. 2005 K.Corbett

The death of Sun-sized stars Once their fuel is used up, the core shrinks and the outer layers begin to expand forming a red giant. Eventually, the star loses enough mass that it becomes a white dwarf. White dwarfs continue to lose heat and eventually become black dwarfs. 2005 K.Corbett

The life of Huge stars Born in a huge nebula (a cloud of gas and dust, mostly Hydrogen). The star produces energy from nuclear fusion of Hydrogen into Helium. This type of star uses up its fuel faster than sun-sized stars. 2005 K.Corbett

The death of Huge stars Once their fuel is used up, the core shrinks and the outer layers begin to expand forming a super red giant. Eventually, the star’s core collapses so much that it explodes in a supernova. This size star will eventually become a neutron star - a star that has about 1.5 times the mass of our sun, but only about 10 km in diameter. 2005 K.Corbett

The life of Giant stars Born in a huge nebula (a cloud of gas and dust, mostly Hydrogen). The star produces energy from nuclear fusion of Hydrogen into Helium. This type of star uses up its fuel faster than sun-sized stars, only living a few million years. 2005 K.Corbett

The death of Giant stars Once their fuel is used up, the core shrinks and the outer layers begin to expand forming a super red giant. Eventually, the star’s core collapses so much that it explodes in a supernova. This size star will collapse on itself so much that it’s gravity takes over completely and not even light can escape. It becomes a black hole. 2005 K.Corbett

Old Age of Massive Stars Supernova Remnants The huge, glowing cloud of debris that expands from a supernova explosion sweeping up interstellar material as it goes is called a supernova remnant Supernova remnants have a more ragged look compared to planetary and other nebulas Two well-known supernova remnants Crab Nebula – Visual outburst witnessed by astronomers in China in 1054 A.D. Supernova 1987A – Most recent visual supernova and a rare blue supergiant explosion Figure 13.20, Figure 13.21, Figure 13.22 2005 K.Corbett 9 9

2005 K.Corbett

Properties of Stars Astronomers classify stars by their color, size, and brightness. Other properties of stars are chemical composition and mass. Color and Temperature – a stars color indicates the temperature of its’ surface. The hottest stars appear blue The cooler stars appear red The spectrum of color in a star is from blues to greens to yellows and reds. 2005 K.Corbett

Brightness The brightness of a star as viewed from Earth is dependent on many factors such as color intensity and distance. Apparent Brightness/Magnitude – is the brightness of a star as it appears from Earth. The apparent brightness decreases as its distance from you increases Absolute Brightness/Magnitude – is how bright a star really is. The absolute brightness is a characteristic of the star and is not dependent on its distance from Earth. 2005 K.Corbett

Hertzsprung-Russell Diagram 2005 K.Corbett

Main Sequence Stars A major grouping of stars that forms a narrow band from the upper left to the lower right when plotted according to luminosity and surface temperature on the Hertzsprung-Russell diagram 2005 K.Corbett

Types of Stars Classification Temperature Color O 20,000- 60,000 K Blue B 10,000 – 30,000 K Blue-white A 7,500 – 10,000 K White F 6,000 – 7,500 K Yellow-white G 5,000 – 6,000 K Yellow K 3,500 – 5,000 K Orange M 2,000 – 3,500 K Red 2005 K.Corbett