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Notes: ASTRONOMY ( pp .775-780) - The study of everything in the universe that can be observed from earth or in space. UNIVERSE Everything that exists ( its’s estimated to be 14 byo) its’ building blocks are the GALAXIES 3 types are spiral, elliptical & irregular groups of STARS glowing ball of GAS gives off ENERGY in the form of RADIATION HYDROGEN & HELIUM (Process called Nuclear Fusion) Wavelengths arranged in the ELECTROMAGNETIC SPECTRUM 4H=1 HE + energy Some wavelengths are invisible & others are VISIBLE LIGHT made of colors ROY G BIV ******************************************************************************************************** STARS Are different distances from earth measured in units called LIGHT YEARS the distance that light travels in a year ( 5.8 trillion mi). *distance= time traveled x 5.8 trillon mi ( or 9.46 trillion km) * Closest star to earth is the sun….next closest is Alpha Centauri , 4.22 light years away. Characteristics of stars: a. Brightness (magnitude)- created by glowing gases. The energy that heats the gases is made from the NUCLEAR FUSION of 4 hydrogen atoms to form 1 helium atom. The helium has less matter than the 4 hydrogen, so the left over matter becomes HEAT ENERGY—makes stars glow ** types of brightness= apparent magnitude & absolute magnitude. b. Temperature- The color tells the surface temperature of the star. red=coolest y-o= medium hot blu-whi= hot blue= hottest The core of stars is very hot. The temperatures observed are of the outer layer of the star. c. Composition- All have nearly identical composition to Earth. 73 % of the stars mass is hydrogen, 25 % is helium & 2% other elements d. Mass/Size- Determined by comparing it to the sun-----Giant, Dwarf and Medium. Most are medium sized like the sun. Fusion occurs more rapidly in larger stars. Some stars are small & dense or large & less dense. Life Cycle of a Star ( pp.781-788) (Stellar Evolution) NEBULA star not hot enough to shine. Nuclear fusion begins & temperature increase in core huge cloud of dust & gas that clump together due to gravity young PROTOSTAR MAIN SEQUENCE TRUE STAR middle-aged star-temperature & brightness are constant for billions of yrs. Hydrogen is slowly used up. GIANT (red) Star begins to die. Shell expands as energy from the core radiates outward. It grows cooler as it expands. Star is bright (LOW MASS) (MASSIVE) WHITE DWARF As the outer gases disperse, the core collapses inward. The hot small core remains & takes billion of years to completely cool off. SUPERGIANT A red giant that keeps expanding Star is very bright and very cool SUPERNOVA Explosion of a star due to the release of energy and great inner core temperature & pressure BLACK DWARF Star no longer giving off light A dead star NEUTRON STAR High densely packed star made from supernova neutrons. Very small & rotates rapidly BLACK HOLE large amount of mass concentrated in a single spot . The gravity is so great making it so dense that not even light can pass thru it. GROUPS OF STARS (pp.790-792) Binary stars Stars that are in pairs. Revolve around each other Held together by gravity Star Clusters A group of hundreds or thousands of stars. Globular and Open Galaxy A system of billions of stars, gas & dust held together by gravity. Major building blocks of the Universe. Universe has 100’s of billion of galaxies ------3 types based on shape: a. elliptical b. irregular- c. spiral Ex. Milky Way Galaxy. Constellations (p.669 &789) Oval shaped, Extremely bright, Older stars No regular shape, Very low mass Made of gas and dust, Least common Looks like a wheel with arm extensions Most common type Arms consist of younger stars, gas/dust. - our galaxy -100’s of billions of stars - it takes 100,000 light years to travel across our galaxy - our galaxy revolves slowly (225 million years) as the stars orbit the center of the galaxy. - galaxies are also in clusters. Our cluster is called the Local Group (30 galaxies) patterns or picture of stars not bound by gravity. 88 constellations specific one’s are only seen during specific times of the year due to the earth’s revolution changing our view of the night sky. OUR STAR: THE SUN - huge glowing gaseous ball found in the Milky Way galaxy. - closest star to earth- 93 million miles away - medium -sized single star. - revolves once every 250 million years. - rotates every 27 days - sun’s surface is constantly in motion due to convection currents. - made of hydrogen & helium. - energy made by nuclear fusion - energy produced is radiation in the form of visible light. - formed 4.6 billion years ago - will live for a total of 10 billion years - it takes energy 8.5 minutes to travel to Earth. - 1 million Earth’s can fit inside the sun.