The Sky From Earth Lesson 1.pptx

The Sky From Earth Lesson 1 Holt What Can You See in the Night Sky? How Do Objects in the Sky Appear to Move? Watching the Stars When you look up at the night sky, what questions do you ask yourself? Do you wonder why the stars seem to move, or why the moon shines? Aryabhata (ar yah BAH tah) w...

The Sky From Earth Lesson 1 Holt What Can You See in the Night Sky? How Do Objects in the Sky Appear to Move? Watching the Stars When you look up at the night sky, what questions do you ask yourself? Do you wonder why the stars seem to move, or why the moon shines? Aryabhata (ar yah BAH tah) was an early Indian astronomer who thought about these questions. He was born in India in A.D. 476 Watching the Stars Many historians think that Aryabhata realized that the stars appear to move from east to west because Earth rotates from west to east. He also wrote that the moon and the planets shine because they reflect light from the sun. And he made all these inferences using just his eyes and his mind. The first telescopes wouldn’t come along for more than a thousand years! Communicate Discuss Aryabhata’s discoveries with a partner. Then answer the questions below. 1. What did Aryabhata infer about the motion of Earth? 2. What questions do you think about when you look at stars, the moon, or the planets? What Can You See in the Night Sky? Depending on how dark the sky is where you are, you might see 2,000 or 3,000 stars using just your eyes. On a clear night, you may see stars, the moon, planets, meteors, and comets. Moon About half of every month, Earth’s moon outshines everything else in the night sky. The moon is Earth’s only natural satellite. A satellite is a body that orbits a planet. Planets You may see objects that move from night to night against the background stars. These are planets. A planet is an object that orbits the sun, is large enough to have become rounded by its own gravity, and has cleared the area of its orbit. There are eight planets in the solar system. Five are visible from Earth without a telescope: Mercury, Venus, Mars, Jupiter, and Saturn. Meteors and Comets Have you ever seen a “shooting star”? These sudden bright streaks are called meteors. A meteor is the streak of light produced when a small object burns up entering Earth’s atmosphere. You can see a meteor on almost any night. Comets are rarer. A comet is a cold mixture of dust and ice that gives off a long trail of light as it approaches the sun. Stars Stars appear as tiny points of light. However, scientists infer that a star is a giant ball of hot gas, mainly composed of hydrogen and helium. As seen from Earth, the positions of stars relative to each other do not seem to change Constellations For thousands of years humans have seen patterns in groups of stars and given names to them. A constellation is a pattern or group of stars that people imagined to represent a figure, animal, or object. Astronomers also use the word constellation for an area of sky and all the objects in that area. Constellations Different cultures have identified different constellations. In Western culture, there are 88 constellations. Most constellation names used today come from the ancient Greeks. Constellations Some constellations’ names come from Latin. The constellation Leo, for example, is named from the Latin word meaning “lion.” Some constellations are named for people or animals in Greek myths. You may have read some of these myths in school. Do the names Pegauss or Perseus sound familiar? They are mythological characters and also constellations. Apply it! 1. Interpret Diagrams Find these constellations on the next slide. Then write each constellation’s name by its picture. 2. Challenge Choose another constellation from the next slide. What does it represent? Do research to find out. How to Use a Star Chart To use a star chart at night, follow these steps. 1. Choose the chart that fits your location and season. This is a summer chart for the Northern Hemisphere. (There are charts for the other seasons) 2. Hold the chart upright in front of you. Turn the chart so the label at the bottom matches the direction you face. (Hint: If you are looking at the Big Dipper, you are looking north.) 3. Hold the chart at eye level. Compare the figures on the bottom half of a chart to the sky in front of you. Finding Constellations A star chart can help you find constellations in the night sky. Read the instructions for how to use the chart. It may seem a little strange at first, but with some practice, these charts are easy to use. Here is one tip to help you get started. Finding Constellations You can probably recognize the Big Dipper. This group of stars is actually not a constellation itself. It is part of the constellation Ursa major or the Great Bear. The two stars at the end of the dipper’s “bowl” are called the Pointers. Finding Constellations Picture an imaginary line between those two stars. If you continue it away from the “bowl” the first fairly bright star you’ll reach is called Polaris (po LA ris). Polaris is commonly called the North Star. It is located close to the sky’s North Pole. Star Chart for all four seasons How Do Objects in the Sky Appear to Move? Stars, planets and other objects appear to move over time. They do move in space, but those actual motions and their apparent, or visible, motions may be very different. The apparent motion of object in the sky depends on the motions of Earth. Star Motions Stars generally appear to move from east to west through the night. As Aryabhata thought, this apparent motion is actually caused by Earth turning from west to east. The sun’s apparent motion during the day is also caused by Earth’s motion. Seasonal Changes Constellations and star patterns remain the same year after year, but which ones you can see varies from season to season. For example, you can find Orion in the eastern sky on winter evenings. But by spring, you’ll see Orion in the west, disappearing below the horizon shortly after sunset. Seasonal Changes These seasonal changes are caused by Earth’s orbit around the sun. Each night, the position of most stars shifts slightly to the west. Soon you no longer see stars once visible in the west, and other stars appear in the east. There are a few constellations that you can see all year long. These are the ones closest to the North Star. As Earth rotates, these constellations never appear to rise or set. Opposite Motions The restaurant on top of Seattle’s Space Needle in Washington rotates much as Earth does. Objects outside appear to move in the opposite direction that the restaurant turn. Predict Draw the mountain as it would appear at each time shown. Planets Planets appear to move against the background of stars, as shown on the last slide. Because the planets all orbit the sun in about the same plane, they appear to move through a narrow band in the sky. This band is called the zodiac. It includes constellations such as Taurus, Leo, and Virgo. Planets Some planets, when they are visible, can be seen all night long. Mars, Jupiter, and Saturn are all farther from the sun than Earth is. Sometimes, Earth passes between the sun. When this occurs, the planets are visible after sunset, once the sun’s bright light no longer blocks the view. Planets You can see Venus and Mercury only in the evening or morning. They are closer to the sun than Earth, and so they always appear close to the sun. Venus is the brightest object in the night sky, other than the moon. Mercury appears low in the sky and is visible for a limited amount of time sunrise or sunset. Assess Your Understanding Objects in the sky appear to move from to _________ because Earth turns from to_________ Explain Assess Your Understanding Make Generalizations What determines whether a planet is visible all night long? Finish the Sentence Today I learned