Unit 1 - Our Planetary Neighborhood

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  • Unit 1 - Our Planetary Neighborhood

    1. 1. The Astronomy Picture of the Day
    2. 2. Our Planetary Neighborhood
    3. 3. Outline • Astronomy • The Earth • The Moon • The Planets • The Sun • The Solar System • The Astronomical Unit
    4. 4. Astronomy (from Wikipedia) Astronomy (Greek: αστρονομία = άστρον + νόμος, astronomia = astron + nomos, literally, "law of the stars") is the science of celestial objects and phenomena that originate outside the Earth's atmosphere, such as stars, planets, comets, auroras, galaxies, and the cosmic background radiation. It is concerned with the formation and development of the universe, the evolution and physical and chemical properties of celestial objects and the calculation of their motions.
    5. 5. The Earth - symbol ♁ • Our home planet. • Spinning ball of rock & metal, coated with a thin layer of gas & liquid. • Huge by human standards, but it is one of the smaller bodies in the cosmic landscape. orbit: 149,600,000 km (1.00 AU) from Sun diameter (D♁): 12,756.3 km mass (M♁): 5.972×1024 kg
    6. 6. The Moon - symbol ☾ orbit: 384,400 km from Earth diameter (D☾): 3476 km mass (M☾): 7.35×1022 kg • Our nearest neighbor, but very different from the Earth • Our only natural satellite • It marks the present limit of direct human exploration of space • Its appearance is different if we are either using our naked eyes (smooth), or a telescope (rocky)
    7. 7. The Planets • In order of increasing distance from the Sun, the eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, & Neptune. These worlds have dramatically different sizes and landscapes. • They range in size from Jupiter (RJupiter = 11 R♁), down to Mercury(RMercury = 0.4 R♁).
    8. 8. The Planets cont. • Our two nearest neighboring planets are Venus (RVenus = 0.95 R♁), & Mars (RMars = 0.53 R♁). Despite their similarities in size & in distance from the Sun, Venus & Mars have dramatically different atmospheres. • On Venus we would be crushed & cooked by its intensely hot, dense atmosphere, whereas on Mars we would suffocate & freeze.
    9. 9. Picture of the eight planets & Pluto (‘dwarf’ planet) along with silhouettes showing their correct relative size
    10. 10. The Sun - symbol • It is a star. • Much bigger than the planets. • It generates energy in its core by converting hydrogen into helium (nuclear fusion) at a furious rate. diameter (D ): 1,390,000 km. mass (M ): 1.989×1030 kg temperature: 5800 K (surface), 15,600,000 K (core)
    11. 11. The Sun cont. • The Sun’s energy is enormous, but limited: it has already lasted more than 4 billion years, and evidence indicates that the Sun will run out of fuel eventually, in about another 5 or 6 billion years. diameter (D ): 1,390,000 km. mass (M ): 1.989×1030 kg temperature: 5800 K (surface), 15,600,000 K (core)
    12. 12. The Solar System • The Sun & the bodies orbiting it form the Solar System, bound together by the enormous gravity of the Sun. • In addition of the eight planets, the Solar System is filled with a vast number of smaller bodies: satellites (moons) orbiting the planets and asteroids & comets orbiting the Sun.
    13. 13. Sketch of the orbits of the planets & Pluto in our Solar System in 2006
    14. 14. A scale model of the Solar System with the Sun the size of a grapefruit
    15. 15. The Astronomical Unit • Distances within the Solar System are not generally given in miles or kilometers. They are given in terms of the astronomical unit (AU), which is defined as the average distance Earth-Sun: • 1 AU = 92,955,800 miles ~ 93,000,000 miles = 149,000,000 km - Distance Jupiter-Sun = 5.2 AU - Distance Neptune-Sun = 30 AU - Distance α Centauri-Sun = 270,000 AU
    16. 16. View of the Solar System based on a series of real images made by the Voyager I spacecraft. A sketch of the orbits of the planets
    17. 17. Key Terms • astronomical unit (AU): • metric system: • planet: • satellite: • Solar System: • star: • unit:

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