Transcript Chapter 39
Chapter 39 The Solar System The Moon Trivia • • • • • • • 1. Is the Moon bigger or smaller than the Earth? 2. What are the large circular features on the Moon's surface? 3. Does the same side of the Moon always face the Earth? 4. How far away is the Moon on average? 5. Who was the first person to walk on the Moon? 6. When was this first moon walk? 7. About how long does it take the Moon to revolve around the Earth? • 8. On the Moon, would you feel lighter or heavier than on Earth? • 9. How many people have stood on the moon? Answers • • • • • • • • • Smaller Craters Yes 239,000 miles Neil Armstrong 1969 1 month Lighter 12 39.1 The Formation of the Moon • We know age, composition, and history of moon • Don’t know how it formed • Several theories – Split off from earth – Came from somewhere else and was pulled in by earth’s gravity – Two large planets collided and made the earth and moon Information on the Moon • The moon is small – Diameter = distance from New York to San Francisco – No atmosphere or weather • Once molten, then cooled • Early on hit often by meteoroids, caused craters we see today 39.2 Phases of the moon • Does the moon always look the same? • Is it always located in the same spot? • Why? – The moon is rotating! – Different amounts of its sunlit half are shown throughout the month – This creates phases 39.2 Phases of the moon • Starts with a new moon – Occurs when moon is between the earth and the sun – What do we see? • Next = Waxing crescent stage – Takes about 7 days – Eventually we see half the moon lit up • Waxing Gibous stage – Another week – We eventually see a full moon – Earth is between the sun and the moon 39.2 Phases of the moon • Cycle reverses over next two weeks • Waning Gibbous until we see half moon again • Waning crescent until a new moon • Whole cycle takes about 29.5 days 39.3 Eclipses • Why are eclipses possible? – The sun is 400 times larger in diameter than the moon – Also 400 times further away – Appear the same size from earth Solar Eclipse • Occurs during new moon • Total eclipse – Darkness during the day – Only seen by 1% of the population in Umbra of the moon – Still see the corona that surrounds the sun • Can have a partial eclipse if in penumbra shadow of the moon • Next solar eclipse will be August, 2008, seen in Canada, Russia, and parts of northern Europe Lunar Eclipse • Occurs at time of full moon • Moon passes into earth’s shadow • Earth’s atmosphere bends the light from the sun – Causes red moon rather than no moon • Occur about twice a year 39.4 One side of the moon • • • • Moon spins about 1 time every 27 days Same rate it revolves around the earth Most moons only show planets one side “Tidally locked” – they are pulled so one side is always facing the planet 39.5 The Sun • Sun’s surface = 5800 K (10,000 degrees Fahrenheit!!), made of plasma – Photosphere – transparent solar surface – Sunspots created by cooler areas – About the size of earth – Move as sun rotates • Chromosphere – just above photosphere The Corona • Corona – outermost region – – – – – Outward moving plasma Kept in by magnetic field Hotter than surface Only seen during eclipse Extends out until it reaches solar wind • Solar wind = high speed electrons and protons – Produces tails of comets – Impacts satellites 39.6 Formation of the Solar System • Sun formed by material pulled together by gravity 5 billion years ago – Early universe had only hydrogen and helium – All other elements were formed in core of stars • Formation of solar systems – Lots of matter (nebula- cloud of gas and dust) pulled together – Center heats up and mass flattens out – Disk begins to cool and planets can start to form 39.7 Planets of the Solar System • • • • Stars are fixed, planets move Planets called wanderers Reflect the light from the sun Divided into Inner and Outer Planets Who Am I? • • • • • • • Largest Planet? Smallest Planet? Has largest rings? Similar size to earth? planets that contain free oxygen? Hottest planet? At least 28 moons? Inner Planets • Mercury – Larger than moon, similar in appearance – 1 year = 88 days – Days are very long and very hot (430 Degrees Celcius) – No atmosphere, nighttime = -170 degrees celcius • Venus – Called “Evening Star” – Similar in size, density, and distance from the sun to earth – Dense atmosphere, high temperatures (460) – Day lasts longer than a year (Year=225 days) – Atmosphere 96% CO2 Inner Planets • Earth – 3rd Planet • Mars – ½ earth’s size, 1/9 its mass – Has a core, mantle, & atmosphere – Mars year = 2 years – 95% CO2, .15% O2 – 30 during day, -130 at night – No water, but dry seabeds – 2 sm. moons Outer Planets • Jupiter – – – – Lgst. Planet Mostly liquid Rotates every 10 hours Pressure 1 million times greater than on earth – Atmosphere = 82% Hydrogen, 17% Helium, 1% Other Gases – 28 moons – Generates more heat than it takes in • Saturn – 2nd largest planet – Large rings = chunks of frozen water and rocks – Mostly hydrogen & Helium – Less dense than water – 23 moons, some rings – Gives off more heat than it takes in Outer Planets • Uranus – – – – Lies on its side Very cold planet 24 moons Faint rings • Neptune – Mainly Hydrogen and Helium – Gives off more heat than it gets from the sun – 8 moons and some rings Pluto, Planet or Not? • Pluto no longer considered a planet – Part of Kuiper belt beyond Neptune – Smaller than our moon – Other similar objects exist, Pluto the largest – 1 year = 248 years – Has a moon 39.10 Asteroids, Meteoroids, & Comets • Asteroid belt – found between Mars & Jupiter • Thought to be material that failed to become a planet • Meteoroids = asteroids less than a few hundred km – – – – Meteor = meteoroid that strikes earth’s atmosphere Usually seen as flash of light (falling star) Called meteorite once it reaches the ground Meteorite impact can lead to mass extinctions (dinosaurs) Comets • Comet = chunk of dust and ice that orbits the sun – Center has the nucleus – solid part of the comet – Trailed by coma – seen as a tail of a comet – Orbit around the sun eliptical, sometimes close, sometimes outside Pluto – Burn out after 100-1000 passes around the sun