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Astronomy and Cosmology Where does the Earth fit in? Formation of the Earth Formation of the Earth Big Bang Galaxies Solar Nebulas Star Formation Planets Beginning of Life Big Bang The theory that states the universe began with a tremendous explosion 12 bya to 15 bya (billion years ago) QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. What is a theory? A theory is well-tested and supported by evidence A theory is widely accepted by scientists A theory can be disproved Galaxies Large grouping of stars in space, formed when chemical clouds gathered after the Big Bang Large galaxies contain more than a trillion (1,000,000,000,000) stars Galaxies Contain gas clouds, open clusters, and globular clusters Gas clouds are also known as nebulas and are generally found in spiral galaxies Open clusters are groups of newly formed stars Globular clusters are groups of older stars Galaxies Types Spiral Elliptical Irregular QuickTi me™ and a T IFF (Uncom pressed) decom pressor are needed to see t his pict ure. QuickTi me™ and a TIFF ( Uncompressed) decompr essor are needed to see thi s picture. Quic kTime™ and a TIFF (Unc ompres sed) dec ompres sor are needed to see this pic ture. We live in the Milky Way Galaxy The Milky Way is a spiral galaxy Our sun is about two-thirds of the way from the center of the Milky Way Star Formation Quic kTime™ and a TIFF (Unc ompres sed) dec ompres sor are needed to see this pic ture. Gravity collects hydrogen and helium to form a star Our sun is an average sized star Planetary Formation Dust gathers to form planetesimals Biggest planetesimal in each orbit swept up all the dust in that path Gas giants collected lots of gases because of large gravitational pull Gases evaporated from inner planets to leave rocky planet Planets Planets rotate on its axis. One rotation is one day. Planets also revolve around the sun. One revolution is one year. Big enough for its gravity to make it a ball Clear the neighborhood around its orbit Revolution vs. Rotation Inner Planets Solid planets Warmer than outer planets Close together Short revolution Mercury, Venus, Earth, Mars Outer Planets Gas Giants (gaseous) Cold Far apart Long revolution Jupiter, Saturn, Uranus, Neptune Dwarf Planets Past outer planets Pluto- formerly a planet Ceres-formerly an asteroid UB313 or Xenadiscovered in 2003 The Moon The moon does not produce its own light It reflects light from the sun Half the moon is always lit, even though we don’t always see the same thing in the sky Phases of the Moon Lunar Eclipse The earth casts a shadow on the moon The moon is in the full moon position QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this pict ure. Solar Eclipse The moon casts a shadow on the earth The moon is in the new moon position QuickTi me™ and a TIFF ( Uncompressed) decompressor are needed to see thi s pi ctur e. Comets Small body of ice, rock, and dust loosely packed together Also known as “dirty snowballs” Tail forms when comet gets too close to the sun Elliptical orbit QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF ( Uncompressed) decompr essor are needed to see this picture. Asteroids Small, rocky bodies that orbit the sun Irregular shapes Different compositions based on where asteroid is found in the asteroid belt QuickTi me™ and a TIFF ( Uncompressed) decompressor are needed to see thi s pi ctur e. QuickTime™ and a TIF F ( Uncompressed) decompressor are needed to see this picture. Meteoroid Quic kTime™ and a TIFF (Unc ompres sed) dec ompres sor are needed to see this pic ture. Small, rocky bodies orbiting the sun Smaller than asteroids A meteoroid is called a meteorite when it comes into the earth’s atmosphere and hits the ground The streak of light that you see when a meteoroid enters the earth’s atmosphere is called a meteor Distances Distances are so far apart in astronomy, so we use Astronomical Units (AU)- average distance between the earth and the sun or about 150,000,000 km (93,000,000 miles) Light Years- distance light travels in one earth year or 9.5 trillion km (9,500,000,000,000) Other Stars…? Our nearest star is Alpha Centauri It is 4.27 light years away or 40,565,000,000,000 km Quic kTime™ and a TIFF (Unc ompres sed) dec ompres sor are needed to see this pic ture.
