Transcript Planets
Celestial bodies: A natural object out in space. Includes: comets planets stars moons asteroids Stars: give off light and heat but are very far away. Ex.The Sun Planets: moving stars. For thousands of years, stars have played important roles in peoples lives: Farmers relied on the presence and the positions of stars to know when to plant and when to harvest their crops. Explorers relied on stars for navigation To tell time and start of seasons Patterns made up of stars. The pattern often looks like a familiar object such as an animal. Constellations are named after Greek and Roman mythology ...stories of kings/queens, villains/heros, animals, etc. 88 constellations have been names, about 20 of which we cannot see in Canada (only observed South of the Equator). Ursa Major (includes the big dipper) is also known as the Great Bear. Orion – depicts a hunter with three prominent stars which form Orion’s Belt. There are 12 Zodiac Constellations which result from the Earth’s rotation around the Sun...which one is yours? Aries Mar. 21- April 19 Taurus April 20-May 20 Gemini May 21 – June 21 Cancer June 22 – July 22 Leo July 23 – Aug.22 Virgo Aug.23 – Sept. 22 Libra Sept. 23 – Oct. 23 Scorpio Oct. 24 – Nov. 21 Sagittarius Nov. 22 – Dec. 21 Capricorn Dec. 22 – Jan. 19 Aquarius Jan. 20 – Feb. 18 Pisces Feb. 19 – Mar. 20 Because the Earth moves around the Sun every year, we see a different part of the sky every season. Some constellations are visible all year long, others are only visible in certain seasons. Celestial bodies move in cyclic paths called orbits. These orbits result from gravitational forces. Planets, suns and moons revolve on a central axis. Stars generally move from east to west. The point around which the stars rotate is the North Star… Polaris. Aristotle (383-322 B.C.E.) Visualized the universe as being geocentric. This means the Earth is the centre of the universe and everything else revolves around it. He believed that the Earth was a sphere due to the curved edges observed during a lunar eclipse. Ptolemy (83-168 C.E.) Based his model on his observations of Mars. Mars orbital path creates a loop or s-shape in the sky. His model showed each planet attached to a crystal sphere with its centre at Earth. Each planet was attached to an off-centre wheel (epicycle). Accepted for nearly 15oo years. Copernicus (1473-1543) Believed in a heliocentric universe (Sun at the centre). The Earth rotated on its axis once daily and revolved around the Sun once a year. **This model set the stage for other scientists to better understand and to propose their own theories based on this model. ** Galileo (1564-1642) First person to view the “heavens” through a telescope. Allowed him to see objects about 20x closer (not very strong but allowed him to see a few celestial bodies). He observed: Craters on the Moon Spots on the Sun Four “stars” orbiting Jupiter (called the Galilean Moons) Galileo’s findings strongly supported the Heliocentric Universe (Sun at the centre). The Catholic Church (Italy) believed in a geocentric universe and put Galileo on trial for his theory...he was found guilty and imprisoned for the rest of his life. Johannes Kepler (1571-1630) Developed 3 Laws of Planetary Motion 1. All planets move in ellipses with the Sun at one focus. 2. Planets sweep out at equal areas of their elliptical orbit in equal times. 3.The time a planet takes to revolve around the Sun is directly related to how far away it is from the Sun. y I Sir Isaac Newton (1643-1727) Developed the three laws of motion. First to show that the force of gravity affects all celestial bodies, causing them to stay in orbit. Scientists use Newton’s laws to calculate how to send people to the Moon and spacecrafts into space. Invented the reflecting telescope which uses a curved mirror to focus the light to a point at an eyepiece. Inner Planets Mercury Venus Earth Mars Jovian Planets Jupiter Saturn Uranus Neptune As technologies advance and improve, our understanding of the universe also improves. Two important inventions to the field of astronomy are: The Astrolabe The Telescope Used to locate and predict the position of the Sun, Moon and stars. Developed around the time of Ptolemy. Along with a compass, it could be used to describe the position of any celestial body in relation to the direction North and to the horizon. Allowed for more accurate observations to be made. The Telescope is an optical (sense of sight) device that uses lenses to gather and focus light to provide a magnified view. The satellites orbiting through space are large telescopes.