Earth in the Universe Unit Notes The Universe - everything everywhere, 15-20 billion years old Inside the universe there are billions of Galaxies Inside each Galaxy there are billions of Solar Systems Origin of the universe : Big Bang Theory 1. The universe started out with all of its matter in a small volume and then expanded outward in all directions from an explosion. (10 20 billion yrs ago) 2. The universe is still expanding outward in all directions. Evidence for the Big Bang Theory 1. Cosmic background radiation can still be detected a. Sensitive radio receivers pick up radiation from all directions. b. This is the "noise" of the explosive birth of the universe. 2. A red shift (Doppler effect) in the spectra of light from very distant galaxies when viewed through a spectroscope. Red shift: Occurs if galaxies and stars are moving away from observer (expanding universe). Picture below shows a red shift. ultraviolet infrared Blue shift: Occurs if galaxies and stars are moving towards observer (contracting universe) Note: This is like what happens with sound waves: As train approaches, the wavelengths apparently shorten and the pitch rises. As train moves away, the wavelengths become longer and pitch becomes lower.
Galaxies 3 Main Shapes 1. Spiral (our own Milky way Galaxy) 2. Elliptical (looks like a football shape) 3. Irregular Our solar system is located in the Orion Arm of the Milky Way Galaxy (Not in the center of galaxy!) Formation of our solar system (after the big bang) 1. Formed about 5 billion years ago from a giant cloud of gas and debris 2. Gravity caused earth and other planets to become layered according to density differences in their materials. 3. The dense, hot gas at center of the cloud became the Sun, the outer regions of the cloud, gave rise to the planets. 4. Since the planets in the solar system formed from leftover material in a disk around the proto-sun, all of the heavy elements in the Earth (including those in humans!) must have come from the same source. This means that in the most literal sense, we are stardust! Parts of Our Solar System Include: (if it orbits the sun, it is part of our solar system) 1. Planets - orbit the sun in elliptical orbits (flattened circles), receive light and energy from the sun. Terrestrial planets (denser, rocky planets closest to sun) Mercury, Venus, Earth, Mars Jovian planets (less dense, larger, gas giants) Jupiter, Neptune, Uranus, Saturn Order from the sun: M VEM J SUN (in ESRT)
2. Moons - bodies that orbits a planet. Natural satellite. 3. Asteroids made of rock, carbon or metal, orbiting the Sun most found in belt between Mars and Jupiter 4. Meteors (the flash of light) Small solid particles caught in earth s gravity are dragged down through atmosphere causing the streak of light we see. shooting star 5. Meteorite a meteor that survives its passage through the Earth s atmosphere and impacts the Earth s surface 6. Comet made of dirt and ice highly elliptical orbits If comet comes near sun, develop tail (partially vaporizes) Don t streak across sky, can be seen for weeks Halley s comet ( every 76 years) (we saw it 1986 ) Hale-Bopp comet (every 2,000 3,000 years) Evidence of Asteroid Impacts on Earth 1. Meteor Crater in Arizona (also called Barrington Crater) 2. Yucatan region, Mexico. 10 km diameter crater from possible asteroid impacting earth. Sedimentary deposits from that era are rich in iridium (rare on earth) Fossils indicate up to 2/3 species became extinct at that time.
One theory: tons of dust thrown into atmosphere, blocking sunlight, cooling earth s climate for many months or years, plants died, plant eaters died, meat eaters died, dinosaurs and other animals became extinct. Kepler s Orbital Laws 1 st Law of Planetary Motion - all planets have elliptical orbits with a star located at one of the focus points. The other focus point is empty space. A planet moves fastest when it is closest to the star (where the gravitational force is strongest). at aphelion, a planet is its farthest from the sun (and moves slower) at perihelion, a planet is its closest to the sun (and moves fastest) 2 nd Law of Planetary Motion - the equal area law. An imaginary line connecting the satellite to the sun sweeps over equal areas of an ellipse in equal amounts of time. Meaning: Area A = Area B if the satellite takes the same amount of time to orbit from position M to position N as it does to orbit from position Q to postion P.
3 rd Law of Planetary Motion The farther a planet is from a star, the longer the period of revolution. In the diagram below, planet Z will have a longer period of revolution than planet Y and X. (It will take a longer time to orbit the star). Apparent Diameter Changes of Celestial Objects The closer a planet is to the sun, the larger the apparent diameter of the sun. The farther away a planet is from the sun, the smaller the apparent diameter of the sun. Sun, moon, planets SEEM TO have change in diameter or size in cyclic manner. WHY? because of change in distance between the earth and these celestial objects due to elliptical orbits. (If orbits were circular, there would be no apparent change in diameters)
Satellite - object that moves elliptically around another object (held in orbit by gravitational attraction) Examples of Satellites - planet around a star, Moon around a planet, Comet around a star Stars - create their own energy by nuclear fusion of hydrogen to helium H + H He Classified by : Temperature (color) & Luminosity (brightness compared to our sun) Chart used to plot and classify stars: Hertzsprung-Russell Diagram (ESRT) Most stars fall in the Main sequence (average or typical stars) Our sun is on the main sequence (not very hot, and not very bright). Life Stages of Stars Stars go through stages according to their mass The sun is now located on the main sequence - 1. It will grow larger, redder, and brighter and become a red giant. Then, the sun will shrink, and become bluer and dimmer. 2. It could become a white dwarf, then black dwarf and give off only a small fraction of the light it does now.