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Chapter 27 Notes. The Sun-Earth-Moon System. Tools of Astronomy. Astronomers study radiation (light) emitted or reflected by distant objects Visible light, radio waves, X-rays, UV, infrared, microwaves, and gamma rays are all types of electromagnetic radiation (EMR)
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Chapter 27 Notes The Sun-Earth-Moon System
Tools of Astronomy • Astronomers study radiation (light) emitted or reflected by distant objects • Visible light, radio waves, X-rays, UV, infrared, microwaves, and gamma rays are all types of electromagnetic radiation (EMR) • All EMR travels at the speed of light • Different types of telescopes detect different types of EMR
Telescopes • A telescope’s purpose is not to magnify objects, but to collect and focus light. • Visible light: • Refracting (lenses) • Reflecting (mirrors) • Radio telescopes:
Space-based Telescopes • Earth’s atmosphere blocks some types of EMR can distort visible light; some telescopes are located above the atmosphere. Here are a few of them: Hubble: visible light Chandra: X-rays Spitzer: Infrared
Space-Based Astronomy • Robotic spacecraft • Cassini (Saturn): 2005 • Mars Reconnaissance Orbiter: 2006 • New Horizons (Pluto): 2006 • Human space flight • International Space Station • Spinoff technology • More than 1400 different NASA technologies passed on to commercial industries
History of the Moon • The Moon is about the same age as the Earth (4.5 billion years old) • Interior: layered, but no tectonic activity • Surface: • Highlands: mountains • Maria: impact basins filled with lava • Rilles: valleys created by flowing lava
Moon Map • A “Mercator” map of the Moon
Formation of the Moon • Impact Theory: Currently accepted theory based on the Moon’s geology and computer simulations
Time is based on Astronomy • Day: one complete rotation (plus ~4minutes) • Year: one complete orbit around the Sun • Month: based on one cycle of lunar phases • Seasons: caused by Earth’s tilt • Solstices: summer and winter • Equinoxes: “equal night” spring and fall • Sun’s maximum height is called the zenith. The zenith varies depending on latitude and time of year
Moon Phases • Waxing: getting larger • Waning: getting smaller • Crescent: less than ¼ size • Gibbous: greater than ¼ size
Lunar month vs. sidereal month • It takes 27.3 days for the Moon to make one complete orbit around the Earth • It takes 29.5 days for the Moon to complete one cycle of phases
Synchronous orbit • The same side of the Moon always faces the Earth • The Moon spins one time on its axis each time it goes around the Earth • There is no “dark side of the Moon”
Solar Eclipse • Earth passes through Moon’s shadow • We see the Sun blocked • Only occurs during new moon phase (why not every new moon phase?)
Lunar Eclipse • Moon passes through Earth’s shadow • We see the Moon darkened • Only occurs during full moon phase