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Astronomy. Astronomy = study of celestial objects and phenomena outside Earth’s atmosphere Includes galaxies, stars, planets, moons, cosmic radiation, etc. Celestial object = Every object outside of Earth’s atmosphere. Space. Universe = includes everything in existence.
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Astronomy Astronomy = study of celestial objects and phenomena outside Earth’s atmosphere Includes galaxies, stars, planets, moons, cosmic radiation, etc. Celestial object = Every object outside of Earth’s atmosphere
Space • Universe = includes everything in existence. ~13.8 billion years old. • Galaxies = collections of billions of stars. Our galaxy is the Milky Way. • Solar System = The Sun and whatever revolves around it (heliosphere). Includes planets, dwarf planets, comets, and asteroids.
Size and Scale Sizes and distances in astronomy are extremely large. Scientists (and the world) use the metric system How many feet in a meter? How many miles in a kilometer? How many grams in an ounce?
Solar System Distances Astronomical Unit (AU) = average distance from Earth to Sun (93 million miles). Mercury is 1/3 of an AU. Neptune is ~40 AU.
Universe Distances Light-year (ly) = distance light travels in a year. Ly = 9.5 trillion kilometers (6 trillion miles) Parsec = 3.3 Ly
Some Distances -- Proxima Centauri (nearest star) = 4.3 light-years away. -- The Crab supernova is about 4,000 light-years away. -- The Milky Way Galaxy is about 150,000 light-years across. -- The Andromeda Galaxy is 2.3 million light-years away.
Sun = soccer ball Mercury = pinhead (10 steps) Venus = peppercorn (19 steps) Earth = peppercorn (26 steps) Mars = pinhead (40 steps) Jupiter = quarter (135 steps) Saturn = nickel (247 steps) Uranus = dime (496 steps) Neptune = dime (777 steps) Pluto = grain of sand (1,019 steps) Light Year = 1,000 miles away Let’s Take a Walk
Size and Distance The Sun is 600x larger than all the planets put together. Using scale from walk: Moon = 2” from Earth Light-year = 1,000 miles Heliosphere = 2,000 miles
Galaxies How many stars in Milky Way? ~200 billion How many galaxies in the universe? ~100 billion (or more) Are there more stars in the universe than grains of sand on Earth’s beaches? 100 stars for every grain of sand on Earth
Hubble Deep Space Field 12 billion light years away. 10,000 galaxies shown. Area = tiny point in space.