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Galaxies Galaxies are huge regions of space that contain the stars, planets, and other astronomical features They can have many shapes Spiral Elliptical Irregular Our galaxy is known as the milky way galaxy Pictures of different shaped galaxies Types of Galaxies Barred-Spiral Spiral Types of Galaxies Elliptical Irregular Milky Way Galaxy 150,000 light years across Spiral shaped with 4 arms We are located in the Orion arm Nearest neighbor is Andromeda (2.2 Million light years) Light Year A light year is the the distance light can travel in one year Light travels at a velocity of 300,000 km per second In one year, light will travel 9,500,000,000,000 km (~10 trillion!) So if the the Milky Way is 150,000 light years across, that is 1,500,000,000,000,000,000 km! OR... If we could travel at the speed of light it would take us 150,000 years to make it across the Milky Way Our Solar System Origin of the Solar System The solar system began as nothing more than dust Gravity caused the dust to condense and spin As the cloud gets hotter and denser fusion takes place The fusion results in the birth of a star Proto – Planetary Disc As our star, the sun, is being formed it is surrounded by a disc of debris and gas These particles interact and accumulate to form the planets When the sun forms it emits solar wind This wind pushes lighter material outward (the gases) Life Cycle of a Star Supernova (SN 1987A) The Sun One of more than 100 billion in our galaxy alone! Rotates about the nucleus of the solar system at about 137 miles/sec Takes about 200 million years to complete a rotation The Sun Cont. Accounts for 99.8% of the mass of our solar system Because it is so massive all of the planets are captured in its gravity field and orbit it Composed of 75% hydrogen and 25% helium The sun is about 5 billion years old and will last for about 5 billion more years The Sun’s Interior The Sun’s Interior Gets its energy from nuclear fusion in which hydrogen atoms are fused together to make energy and light The core is about 15 million °C The Atmosphere of the Sun Photosphere - inner layer that is responsible for the light Chromosphere middle layer that produces the red color you see at eclipses Corona - outer layer that is only visible during an eclipse Other Parts of the Sun Sunspots - dark spots on the sun that are areas of gas that are cooler than gases around them Prominences - huge loops of gas that connect different parts of sunspot regions Solar flares explosions of hydrogen Geocentric vs. Heliocentric Prior to Copernicus and Galileo, people thought that the Earth was the center of the universe and all things orbited around the Earth This is know as the Geocentric model Based on their observations, Copernicus and Galileo were able to prove that the sun was the center of the solar system This is the Heliocentric model