Planetarymotionhistoricalpeopleinastronomy 131204162554-phpapp02
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The universe contains billions of galaxies, each with billions of stars. A galaxy is a group of stars held together by gravity, and the main types are spiral, elliptical, and irregular. Stars are formed from the collapse of large clouds of dust and gas, releasing heat and light through nuclear fusion. Our solar system contains 8 planets that orbit the Sun, including Earth. Copernicus first proposed the heliocentric model that planets orbit the Sun, with Kepler developing the laws of planetary motion. Newton later explained that gravity and inertia cause planets to follow elliptical orbits around the Sun.
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Planetarymotionhistoricalpeopleinastronomy 131204162554-phpapp02
- 2. THE UNIVERSE The Universe contains billions of galaxies with each galaxy containing billions of stars. Universe is always evolving. Everything that exits in the universe is not permanent. New stars are being born while existing stars will eventually die. The Universe is all matter and energy.
- 3. THE GALAXIES A Galaxy is a group of stars held together by gravity. There are billions of Galaxies. There are hundreds of billions of stars in a Galaxy. The main three types of Galaxies are - Spiral Galaxy - Elliptical - Irregular
- 8. Formation of Stars Stars are formed within large clusters of dust and gases called as nebulae. Due to the force of gravity nebula collapses and spin. The spinning clouds pull in more hydrogen gas over millions of years. Collisions occurred between nebula and hydrogen atoms. Hydrogen atoms combine to form helium atoms, releasing a large amount of heat and light
- 9. Energy is produced in a star's center, or core, where pressures are enormous and temperatures reach 27 million°F (15 million°C). This causes nuclear fusion—atoms of hydrogen are ripped apart and fuse (join) to form helium. These reactions release vast amounts of energy, which makes the starshine.
- 10. Overview of our Solar System Earth is one of the 8 planets revolving around, or orbiting, the sun. We live in the Milky Way Galaxy( Spiral)!
- 11. The Milky Way Galaxy It is the name of our Galaxy. It has spiral shape. It contains 200 billions stars. Sun is one of the star in Milky way
- 12. We get the term "planet" from the Greek word "Planetes" - meaning wanderer Astronomers of the International Astronomical Union (IAU) voted on and passed the first scientific definition of a planet in August 2006. According to this new definition, an object must meet three criteria in order to be classified as a planet. First, it must orbit the Sun. Second, it must be big enough for gravity to squash it into a round ball. What is a Planet
- 13. Why are Planets Round? This balance is called hydrostatic equilibrium. A star is like a balloon. In a balloon the gas inside the balloon pushes outward and the elastic material supplies just enough inward compression to balance the gas pressure. In a star the star's internal gravity supplies the inward compression.
- 14. All the planets, as well as most of their moon (satellites), orbit the Sun in the same direction, and all their orbits, lie near the same plane. Planets, stars, comets and galaxies make a solar system.
- 15. We have gathered much information through the use on modern technology. Spacecraft, telescopes (ground based & space based).
- 16. 3. Copernicus (1473 – 1543)
- 17. Copernicus… 1st to propose that planets ORBIT around the Sun (Heliocentrism). CONTROVERSIAL at the time!!!
- 18. 2. Tycho Brahe (1546 – 1601)
- 19. Made important contributions by devising the most precise instruments available before the invention of the telescope for observing the heavens. The astronomical instruments of Tycho Brahe Tycho Brahe
- 20. Brahe cont… Brahe proposed a model of the solar system that was intermediate between the Ptolemaic and Copernican models (it had the Earth at the center). It proved to be incorrect, but it was the most widely accepted model of the Solar System for the time.
- 21. Brahe cont… His observations of planetary motion, particularly that of Mars, provided crucial data for later astronomers like Kepler to construct our present model of the solar system.
- 22. 5. Kepler (1571 – 1630) Developed the 3 laws on planetary motion. Described how planets moved around the sun.
- 23. 1st Law (Eccentricity): The orbit of each planet is the shape of an ellipse (oval –shaped) with the sun located at one focus. (There are 2 foci in an ellipse).
- 24. 2nd Law (Law of Equal Areas): In any time interval, a line from a planet to the sun will sweep out equal areas. NOTE: As the planet goes around the sun, the further away it is, the slower it ORBITS. This is due to the gravitational attraction between the Sun and Earth. A planet sweeps out at equal amounts of area in equal amounts of time.
- 25. 3rd Law (Law of Harmonies) The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. P2 = a3 P = time2 it takes to go around the sun. A = distance3 from the sun.
- 26. Using the 3rd Law (write out): We can use the 3rd law to find: a) Distance from sun. b) Orbital period of a planet.
- 27. Let’s try… Determine the orbital period: Planet Distance from Sun (AU) Orbital Period P2 = a3 Mercury 0.387 Venus 0.723 Earth 1 Mars 1.524 Jupiter 5.203 Saturn 9.539 Uranus 19.191 Neptune 30.071 Pluto 39.457 0.241 0.616 1 1.88 11.9 29.5 84.0 165.0 248.0
- 28. The Earth’s Stalker The Moon stays in orbit because of Earth's gravity. Gravity is a force that pulls objects toward each other. Just because an object is big does not mean it will have lots of gravity. The force of gravity depends on an object's mass. The gravity on the Moon is about 17% what it is on the Earth. So if you weigh 200 pounds on Earth, you will weigh 34 pounds on the Moon.
- 29. What causes Tides The Moon causes tides.
- 30. Leap Year Only happens every 4 years, on February 29th. The earth takes 365.25 days to orbit, so it leaves and extra day every four years.
- 31. Changes We have seasons because the earth is tilted (wonky) as it makes its yearly journey around the sun. The Earth's axis is tilted at an angle of 23.5 degrees. This means that the Earth is always "pointing" to one side as it goes around the Sun.
- 32. Precession Change in the direction of the axis.
- 33. Wobble, Wobble, Wobble, Wobble Nutation
- 34. Barycenter The point between two objects that balance.
- 35. Newton’s view on planetary motion… Newton proposed that the planet’s motion is due to 2 forces: Inertia and gravity. When combined, the planets move in an elliptical orbit.
- 36. When planet is at its farthest point from the sun. 93 million miles!!! Aphelion
- 37. Perihelion When a planet is at its closest point from the sun. 91 million miles!!!
- 38. Planet will “sweep” faster here. Planet will “sweep” slower here. Gravity gets stronger as the planets come “near” the sun. Time: AB = CD
- 39. 2. Sun’s gravity pulls Earth. 1. Earth’s tendency of movement is in a straight line (Inertia). Combined, it causes the planets to orbit around the sun.
- 40. Rotation The time it takes for a planet spin or rotate on its axis once. Examples: a) Earth = 24 hours b) Mercury = 59 days
- 41. Revolution The time it takes for a planet to go around the sun once. Examples: a) Earth = 1 year b) Pluto (dwarf planet) = 248 years