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Download CHAPTER 2 NOTES (STARS AND GALAXIES)
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2-1 Multiple-Star Systems- more than one star Ex triple-star (3) system- Alpha Centauriclosest star system to our sun Ex double-star (2) system (Binary stars)- Algol (ghoul) Our Sun- single star system, which is the closest star to Earth Constellations- groups of stars in which people at one time thought they saw imaginary figures of animals and people: ex Ursa Minor (Little Bear)- containing the Polaris (North Star) Orion (Hunter)- containing the bright supergiant stars, Betelgeuse and Rigel Siruis (Dog Star)- middle sized star, which is the brightest star in the night sky Nova- a star that suddenly increases in brightness up to 100 times in just a few hours to days then grows dim again (maybe because of a companion star’s gases that strike its surface, causing explosions) 2 types of cluster stars: 1. open clusters- not well organized ex Pleiades 2. globular clusters (more common)- arranged in spherical or round shape Nebula- huge clouds of dust and gas, probably the birthplace of new stars Galaxy- huge collection of stars 3 types of galaxies are: 1. spiral- arms like a pinwheel ex our galaxy- Milky Way 2. elliptical- nearly spherical to flatdisks (older than other galaxies) 3. irregular- no orderly or definite shape, not very common Milky Way Galaxy- pinwheel shaped disk with bulge in center -the older stars are near the center nucleus -our sun is on one of the spiral arms because it is younger 2-2 spectroscope- breaks up the light from a distant star into its characteristic colors Stars rapidly approaching the Earth have light waves from the star that will be compressed (pushed together) and appear shorter- blue and violet light (blue shift) Stars moving away from the Earth have light waves from the star that will be expanded and appear longer- red (red shift) Doppler effect- apparent change in the wavelengths of light that occurs when an object is moving toward or away from Earth Every galaxy in the universe is moving away from the Earth, therefore the universe is expanding Big-Bang- states that the universe began to expand with the explosion of concentrated matter and energy and has been expanding ever since Background radiation supports the Big-Bang theory because energy left from it should be evenly spread out throughout the universe Open, eternal universe- universe that will continue to expand and lead to total emptiness Closed universe- universe that periodically expands and then contracts back on itself Quasars (quasi-stellar radio sources)- most distant known objects in the universe (12 bil light-yr) -Starlike objects that give off tremendous amounts of energy in the form of radio and x-ray waves -Thought the be the earliest stage of galaxy, at the very edge and very beginning of universe 2-3 5 sizes of stars: Neutron star- smallest (approx. 16 km) White Dwarf- smaller that the continent of Asia (Van Maanen’s star is smallest) Middle-sized star- majority of stars, like our Sun Giant star- 10 to 100 times larger than our Sun Supergiant star- 1000 times larger than our sun Mass is determined by composition (what it is made of)- determined by spectroscope “fingerprint” or a characteristic set of lines of the element hydrogen- the most common element of a star makes up 60% - 80% of the total mass helium- the second most common element of a star (hydrogen and helium is 96% - 99%) other elements such as oxygen, neon, carbon, and nitrogen make up 4% of the star’s mass Color is a good indicator of the surface temperature of a star. Hottest- blue or blue-white color (50,000oC) Coolest-red (3000oC) Brightness- depends on the star’s size, surface temperature and distance from Earth Apparent magnitude- brightness as it appears from Earth Absolute magnitude- actual brightness Pulsating variable star- changes in brightness and size ex Polaris Hertzsprung-Russell diagram (H-R diagram)relationship between absolute magnitude (brightness) and temperature- as the absolute magnitude (brightness) increases then the temperature increases x-axis surface temperature y-axis absolute magnitude (actual brightness) main sequence stars make up 90% of the stars in the sky Distance depends on how far away from Earth a star is: 1. Parallax (close to Earth)- apparent change in position of a star in the sky, which would change because of the Earth’s position as it moves around the sun 2. Use Brightness (more than 100 light-years from Earth) 3. Spectroscope (more than 7 mil light-years from Earth) Nuclear Fusion- why stars shine -gravity pulls together the hydrogen gas atoms in the core so they fuse to form helium releasing energy in the form of heat and light 2-4 Our sun- middle-aged, medium sized yellow star approximately 4.6 billion years old in terms of size, temperature, and mass 4 main layers of the sun: 1 interior layer- core where hydrogen changes to helium in nuclear fusion 3 atmosphere layers- 1. corona- outer most 2. chromosphere- middle layer 3. photosphere- inner most layer Solar storms: prominences- arches or loops of gas solar flares- bright bursts of light on the sun’s surface solar wind- continuous stream of high-energy particles released into space in all directions can interfere with radio and telephone signals sunspots- dark areas on the sun’s surface (cooler than the rest of the sun’s surface interfere with Earth’s communication in 11 year cycles The sun rotates on its axis (imaginary vertical line through the center of the sun)