Astronomy, PART 2 Vocabulary Aphelion Asteroid Astronomical Unit Comet Constellation Crater Eccentricity Eclipse Equinox Geocentric model Gravitation Heliocentric model Inertia Jovian Perihelion Revolution Rotation Lunar Penumbra Seasons Solstice Tropic of Cancer Tropic of Capricorn Terrestrial Tides Umbra Astronomy - I. Earth s Place in the Universe A. Universe - Our Milky Way Galaxy is one of of galaxies in an expanding universe. B. - Our Sun/solar system is one of an estimated stars making up this spiral galaxy C. Our Solar System - Earth is a small, dense one of that orbit the sun. D. The Gas GIANTS or E. Asteroids, Comets, and Meteoroids Asteroids - Small, rocky bodies that orbit the Sun. The is located between and. Comets - Body of methane, ammonia,and 1
Orbit the sun in long Made of 3 parts: made of rock, metals, and ice cloud of gas and dust surrounding the nucleus gas and dust streaming from the head and always points AWAY from the sun - small bits of rock or metal that move throughout the solar system - once it enters Earth s atmosphere most burn up in the atmosphere and produce a long streak, which is known as a occasionally large numbers enter the atmosphere in a short period of time, creating a - if the meteor doesn t burn up completely in the atmosphere and strikes Earth II. Measuring Distance A. Light Year The speed of light is 186,000 mi/sec. a. We see all night stars as they WERE when the light. When we look at distant stars and galaxies, we look back in. B. Astronomical Unit 1 AU = The distance between! III. Models of the Universe A. Geocentric Model A. About 2000 years ago, the Greek astronomer, Claudius developed a detailed model of the universe based on the. idea of 2. In this model of the universe, was at the center, and all heavenly bodies in. 3. Ptolemy s geocentric model, as illustrated on the next page, can be summarized as follows: 2
a. Earth is located in the and does not move. b. The are located on a transparent sphere that rotates once each day from to around Earth. c. The the and each are carried by separate spheres of different sizes. d. Each planet is located on an that also rotates. This explained - e. This model was accepted for almost 1400 years because it explained celestial observations made from Earth and it seemed obvious. B. Heliocentric Model Copernicus heliocentric model can be summarized as follows: 1. The is located in the of the system and does NOT move. 2. The are located on a stationary/unmoving transparent sphere. The sphere is a great distance from the sun. 3. The including move in around the sun. 4. The moves in a circle around. 5. rotates on its axis from west toward east each day. HOWEVER Copernicus heliocentric model does NOT explain the apparent cyclic variations in the size of the Sun, and the cyclic variation in orbital speeds of the planets. This is because in the heliocentric model,. 3
C. Johannes Kepler 1. In 1609, published a book which included his first 2 Laws of Planetary Motion. These laws explain why the apparent size of the sun changed, and why the speed of a planet changes as it orbits the Sun. a. Kepler s 1 st law: The orbit of each planet is an with the sun at one focus and an imaginary point in space at the other focus. An ellipse looks like an oval, or squashed circle. The longest line drawn from one end of the ellipse (through the center) to the other side is called the. For a circle, the two foci lie on top of each other. 4
Eccentricity can be calculated as e = Distance between the foci = degree of the out-of-roundness of an ellipse. Length of the Major Axis The eccentricity of a circular orbit is, and can range from zero to less than for an ellipse. Relationship: As the distance between the focal points, the shape of the ellipse becomes more oval (Line = 1) b. Kepler s 2 nd law: describes the fact that Area A = Area B 1. = Point in orbit when object is nearest the sun. 2. = Point in orbit furthest from sun c. Kepler s 3 rd law: The further a planet is from the sun, the it s period of revolution! 1. Farther planets have orbital paths 2. Farther planets have orbital paths D. Sir Isaac Newton 1. Newton s Laws of Gravity a. 1 st Law: and will pull all other objects with a certain gravitational force. b. 2 nd Law: The mass of an object will determine the amount of gravitational force that object possesses. The the mass, the the gravitational force. c. 3 rd Law: The gravitational force between 2 objects changes as the distance between them change. As the distance gravitational pull will. 5
The Inverse Square Law: If you half the distance between two objects, you quadruple the gravitational force between them. 2. Gravity and Inertia a. Newton s Law of Inertia states that a body in motion will continue in motion unless acted on by an. INERTIA + GRAVITY = IV. Rotation - A. Earth s Direction of Rotation: to Angular Rate of Rotation: THINK one complete rotation degrees hours Rate = 360 /24 hours = B. Effects of Earth s Rotation 1. and 2. Apparent daily motion of a. Earth rotates from to b. Sun appears to move in an arc from to Earth is NOT a perfect sphere. It is an equator (due to its rotational spin) slightly wider across the 6
Earth s axis is not stable. It moves/wobbles (like a top). This is known as very slow - 26,000 years to complete one cycle. Within the precession are additional motions known as smaller motions back and forth as the precession occurs.. It s. These are IV. Revolution The of one celestial body around another object. A. Earth s Angular Rate of Revolution 1. degrees (Think CIRCLE) 2. days 3. Rate = 360 /365 days ~ = B. Effects of Earth s Revolution 1. Nighttime constellations change in a yearly cycle. 2. groups of stars that form patterns of imaginary things such as animals, legendary heroes, and mythological gods. 3. A yearly cycle 5. Seasons of the Year A. Causes: 1. - Earth revolves around the sun 2. - Earth is tilted/inclined on axis 23 1/2 o 3. - Earth s axis always points in the same direction. 7
B. Earth s axis is tilted relative to the plane of it s orbit. (Draw and label your diagram according to the diagram at the right. Be sure to name the equator, the Tropic of Cancer and Capricorn and note where we live.) C. The apparent path of the sun changes with the and with. D. Length of Daylight (duration of daylight) changes with and with. E. Factors Affecting Insolation 1. Shape of the Earth ( ) 2. As latitude increases, the angle of insolation and the intensity of insolation 3. Season of the Year a. As Earth travels along its orbital path around the sun, the angle of insolation at a given latitude changes with the seasons. This depends on how far a given latitude is from the direct rays of the sun. The direct rays migrate between the and the 8
4. Time of Day a. The angle of insolation changes in the course of one day. Maximum intensity occurs at. b. Looking South A. The shadow of a vertical pole indicates how the angle of insolation changes during the day. The higher/greater the insolation, the the shadow, and the the intensity of insolation. 9
VI. The Moon A. The Moon is a. 1. - is Latin for Moon. 2. - Roman Goddess of the Moon. B. Physical Properties of the Moon 1) Size 2) Atmosphere i. Diameter = miles. ii. Compared to the Earth: 1. Diameter = Moon Earth 8000 2. Gravity: a. the gravity of Earth. b. This is because the Moon has a. The Moon has. b. Gravity is too weak so c. Without an atmosphere radiation from the sun is d. You would get a sunburn in seconds. e. Frozen water may exist at the Moon s but no liquid water would exist. 3) Temperatures a. It is on the lighted side of the Moon. b. It is on the far side of the Moon. 10
c. These large temperature extremes exist because 4) Lunar Topography a. - bowl-shaped depressions formed primarily as a result of impact of meteors. i. Most cratering occurred during a heavy bombardment period which gave Earth it s early CO2 atmosphere 4 billion years ago. ii. There are many more craters on the Moon than on the Earth because. b. - smooth glassy regions, which are generally craters filled in by lava. c. The surrounding rough regions are called 5) The Moon s Revolution a. Period of Revolution = or b. The Moon travels around the Earth in an orbit with the Earth at one c. This causes the Moon s apparent to change in a manner. 11
6) Phases of the Moon a. The phases of the Moon are caused by the moon s. b. This is an Earth view of the changing illuminated part of the Moon s surface that faces the Earth. c. - the decrease in light (on the left); from full moon to new moon. d. - the increasing of the Moon s visible illuminated surface (on the right); from new moon to full moon. Phases Phase #1 _ - when the Moon is roughly in the same direction as the sun, it s illuminated half is facing away from the Earth and therefore the part that faces us is all dark. Phase # 2 Phase # 3 Phase # 4 Phase # 5 Phase # 6 Phase # 7 Phase # 8 12
7) Moon Rotation? a. The same side of the Moon always faces the Earth. b. Does this mean that the Moon doesn t rotate? c. YES IT DOES!!!. 8) Lunar Eclipse a. An eclipse of the Moon can only take place at and only if the Moon passes through some portion of the Earth's shadow. The shadow is actually composed of two cone-shaped components, one inside the other. The outer or shadow is a zone where some portion of the Sun's rays are blocked. In contrast, the inner or shadow is a region devoid of all direct sunlight. 9) Solar Eclipse a. A Solar eclipse occurs when the passes directly between the Earth and the Sun. b. are the only time solar eclipses occur. 13
10) Tides a. Tides are the alternate and of the sea b. This is caused by the gravitational pull on the surface waters. c. The rising of tides is affected by the position and d. The period from high tide and high tide is normally about hours and minutes. e. Tides are a change. 14