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Earth in the Solar System (Earth Science) 12% 7 Items Test Prep Questions 8th Grade (4a Earth in the Solar System) Students know galaxies are clusters of billions of stars and may have different shapes. Summary: Stars are not uniformly distributed throughout the universe but are clustered by the billions in galaxies. Galaxies themselves appear to form clusters that are separated by vast expanses of empty space. As galaxies are discovered they are classified by their differing sizes and shapes. The most common shapes are spiral, elliptical, and irregular. 8th Grade (4b Earth in the Solar System) Students know that the Sun is one of many stars in the Milky Way galaxy and that stars may differ in size, temperature and color. Summary: The Sun is a star located on the rim of a typical spiral galaxy called the Milky Way and orbits the galactic center. In similar spiral galaxies this galactic center appears as a bulge of stars in the heart of the disk. Stars vary greatly in size, temperature, and color. For the most part those variations are related to the stars’ life cycles. -------------------------------------------------------------Illinois Released Question White dwarfs are hot stars that produce very little light. In which zone would a white dwarf be found? A B C D Zone 1 Zone 2 Zone 3 Zone 4 Answer: A Zone 1 -------------------------------------------------------------- 8th Grade (4c Earth in the Solar System) Students know how to use astronomical units and light years as measures of distances between the Sun, stars and Earth. Summary: Distances between astronomical objects are enormous. The astronomical unit (AU) is defined to be equal to the average distance from Earth to the Sun: 1 AU=1.496X1011meters. Distances between planets of the solar system are usually expressed in AU. For distances between stars and galaxies, even that large unit of length is not sufficient. Interstellar and intergalactic distances are expressed in terms of how far light travels in one year. 1 light year = 9.462X1015meters, or approximately 6 trillion miles. The most distant objects observed in the universe are estimated to be 10 to 15 billion light years from the solar system. 8th Grade (4d Earth in the Solar System) Students know that stars are the source of light for all bright objects in outer space and that the Moon and planets shine by reflected sunlight, not by their own light. Summary: The energy from the Sun and other stars, seen as visible light, is caused by nuclear fusion reactions that occur deep inside the stars’ cores. By carefully analyzing the spectrum of light from stars, scientists know that most stars are composed primarily of hydrogen, a smaller amount of helium, and much smaller amounts of all other chemical elements. Most stars are born from the gravitational compression and heating of hydrogen gas. A fusion reaction results when hydrogen nuclei combine to form helium nuclei. This event releases energy and establishes a balance between the inward pull of gravity and the outward pressure of the fusion reaction products. Planets and the Moon do not generate the light that makes them visible. -------------------------------------------------------------Virginia State Released Question What element is the main component of most stars? A Nitrogen B Iron C Hydrogen D Oxygen Answer: C Hydrogen -------------------------------------------------------------- 8th Grade (4e Earth in the Solar System) Students know the appearance, general composition, relative position and size, and motion of objects in the solar system, including planets, planetary satellites, comets, and asteroids. Summary: Nine planets are currently known in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. They vary greatly in size and appearance. The planets also drastically vary in their distance from the Sun, period of revolution about the Sun, period of rotation about their own axis, tilt of their axis, composition and appearance. The inner planets (Mercury, Venus, Earth and Mars) tend to be relatively small and are composed primarily of rock. The outer planets (Jupiter, Saturn, Uranus, and Neptune) are generally much larger and are composed primarily of gas. Pluto is composed primarily of rock and is the smallest planet in the solar system. All the planets are much smaller than the Sun. All objects are attracted toward one another gravitationally, and the strength of the gravitational force between them depends on their masses and the distance that separates them from one another and from the Sun. -------------------------------------------------------------Virginia State Released Question One complete revolution of a planet around the sun equals one A B C D year month week day Answer: A year -------------------------------------------------------------Illinois State Released Question If all the planets started out together on their trips around the Sun, Which one would finish the trip last? A B C D Jupiter Pluto Mercury Saturn Answer: B Pluto -------------------------------------------------------------- Virginia Released Question Planet Earth Jupiter Mars Mercury Venus Average Distance from Sun (Kilometers-Km) 149.5 million Km 777.3 million Km 227.9 million Km 57.9 million Km 108.2 million Km According to this chart, which planet will most likely have the highest temperatures? A Earth B Mars C Mercury D Venus Answer: C Mercury --------------------------------------------------------------