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Sun, Earth, Moon Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Cartoon of the Day “From now on we live in a world where man has walked on the Moon. It's not a miracle; we just decided to go. “ -- Tom Hanks Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Announcements COLLEGE OF THE CANYONS • Canyon Country Campus Join us for a • • CoC Star Party tomorrow Grading up to date! STAR FORMATION: Light Beyond The Visible Presented by Dr. Luisa Rebull Research Scientist, SSC and IRSA, IPAC, Caltech Featuring: • Hands-on interactive demonstrations and activities • COC student clubs and academic departments highlighting innovative approaches to understanding the science that governs the universe • Gaze at the stars through a variety of telescopes Friday, OCT 16 7 – 9:30 p.m. Carl A Rasmussen Amphitheater College of the Canyons Canyon Country Campus 17200 Sierra Highway, Santa Clarita, CA 91351 Tallest Tower Building Competition Sign-up online! www.canyons.edu/Offic es/ CCC/Pages/StarParty.a spx LA Mission College F THE C • COLLE N A NS • YO Astronomy 1 - Elementary Astronomy CA www.canyons.edu/ccc EO N For more information visit G Food and beverages will be available for purchase YO N RY • HW Kepler, Gravity Light due Star Party C OU NT Levine F2015 Last Class • • • • Midterm debrief Multi-wavelength Astronomy Intro to the Solar System LT Sun Size (completed, not debriefed) Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 This Class • • • • • Grade Status Debrief LT Sun Size & do questions Sun Earth Moon Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Grade Status Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Grade Status Letter Midterm Course A 9 13 B 7 18 C 14 8 D 12 4 F 7 6 Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Debrief LT Sun Size Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 The Sun has a diameter of approximately 1.4 million kilometers. Roughly how many Earths would fit across the diameter of the Sun? A. 10 B. 100 C. 1000 D. 10,000 E. 1 million Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Let’s Practice sunspots. How does the size of Earth compare to the size of the sunspot that is identified on the right side of the image of Sun? The image at right shows a a) Earth and the sunspot are about the size. Sun. The dark picture same of the b) The sunspot is much, much larger than spots located on this image Earth. c) The sunspot is much, much smaller than are sunspots. How does the Earth. size of Earth compare to the size of the sunspot that is identified on the right side of the image of Sun? 2) Which statement do you think best represents the size comparison between the diameter of the Sun and the distance between the Moon and Earth? The Sun’s diameter is a) smaller than the distance between the Moon and Earth. b) approximately equal to the distance between the Moon and Earth. c) larger than the distance between the Moon and Earth. A. Earth and the sunspot are about the same size. B. The sunspot is much, much larger than Earth. 3) If you were constructing a scale model of the solar system that used a Sun that was the size of a basketball (approximately 12 inches in diameter), which of the following lengths would most closely approximate the scaled distance between Earth and the Sun? a) 3 feet (length of an outstretched arm) b) 10 feet (height of a basketball goal) c) 100 feet (height of an 10 story building) d) 300 feet (length of a football field) C. The sunspot is much, much smaller than Earth. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Which statement do you think best represents the size comparison between the diameter of the Sun and the distance between the Moon and Earth? The Sun’s diameter is A. smaller than the distance between the Moon and Earth. B. approximately equal to the distance between the Moon and Earth. C. larger than the distance between the Moon and Earth. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 If you were to construct a scale model of the solar system that used a 2 cm cherry to represent the Moon, how large of a ball would you need to represent the Sun? A. 4cm B. 30cm C. 110 cm D. 440 cm E. 880 cm Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The Sun Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 THE SUN IS A STAR What is a star? • A sphere of hot gas • • mostly hydrogen & helium Interior hot enough to undergo nuclear fusion in core • core above 107 K = 10 million K (18 million °F) Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Why Stars Shine • • Visible Sun is a hot layer of gas • about 5800 K (5525°C, 9980°F) • not as hot as the center! Gives off light the same way that hot metal glows red, yellow or white • • Thermal radiation or blackbody This is why stars have different colors Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Basic Data http://www.kidsgeo.com/geography-for-kids/0003-how-big-is-the-earth.php • • Fairly average star It rotates • • • • faster at the equator (25 days) than at the poles (31 days) Entirely gas: Hydrogen (80%) and Helium (19%) Central Temperature 15,000,000 K Surface Temperature 5800 K Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 What Type of Star is the Sun? • Main Sequence Star • most stars spend most of their “life” on the Main Sequence • energy source thermonuclear fusion • H fusing to He in the core Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 What Type of Star is the Sun? • • Spectral Type G2 Lifetime on Main Sequence 10 billion years Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The structure of the Sun Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The structure of the Sun • Core • • • compact: center to about 25% radius 15 million K atoms completely ionized • • e- “blasted off” Where thermonuclear fusion is taking place. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The structure of the Sun • Radiative zone • • • 0.25 - ~ 0.7 solar radii Energy from core transferred by EMR Convective zone • • above radiative zone Energy transferred to surface by convection Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Convection Cool gas sinking down Astronomy 1 - Elementary Astronomy Bubbles of hot gas rising up LA Mission College Levine F2015 Let’s Practice The Sun’s Luminosity comes primarily from A. chemical burning B. gravitational contraction C. nuclear fusion D. nuclear fission Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The energy produced by the Sun is produced A. in a very small region at the center of the Sun B. Uniformly throughout the Sun C. At the surface of the Sun Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 THE OUTER LAYERS OF THE SUN The structure of the Sun • Photosphere • Visible surface of the Sun • Apparently smooth layer of gas • • • 500 km thick 5800 K Sunspots Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Granulation • Up close, photosphere has a mottled appearance (granulation) due to convection cells. • These cells form and fade and shift on a time scale of tens of minutes. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Sunspots • well-defined surface areas that appear darker than their surroundings because of lower temperatures. • Associated with sun’s magnetic field • convection is inhibited by strong magnetic fields, reducing energy transport from the hot interior to the surface Astronomy 1 - Elementary Astronomy http:// LA Mission College Levine F2015 The structure of the Sun • Chromosphere • Atmospheric layer above the photosphere. • 1000x fainter than the photosphere, but hotter! Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The structure of the Sun • Chromosphere • Pink color during a total eclipse. • Filaments (dark regions) & Spicules/prominences (jets). Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Solar Prominence Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Let’s Practice Sunspots appear dark because A. They are holes in the photosphere allowing a view of deeper layers B. Are large opaque structures that block the light from the interior C. Are slightly cooler than the surrounding areas, appearing dimmer D. Are burning holes in your retina Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 THE CORONA, SOLAR WIND AND SOLAR WEATHER The structure of the Sun • Corona • Outermost atmospheric layer. • Extending outwards 20 times the Sun’s radius. • Heated by magnetic field interactions. • solar wind • • 300 - 1000 km/s Loses 10 million tons/yr http://antwrp.gsfc.nasa.gov/apod/ap080920.html Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Solar Weather (Ultraviolet images) • In addition to sunspots, solar activity results in • • • • • Solar flares Aurora Borealis Coronal Mass Ejections Geomagnetic Storms http://spaceweather.com/, http://www.swpc.noaa.gov/ Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Aurora Borealis Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Solar Weather and Humans • Solar flares • • Coronal Mass Ejection • • really refer to increased brightness Interferes with Satellites Geomagnetic Storms • In rare cases causes power grid issues Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 FATE OF THE SUN Endgame for our Sun • A star’s fate is pretty much determined at the moment of it’s “birth” by its mass • • High mass stars, ~ 8x Sun, explode • • and the company it keeps supernovae Low mass stars like the Sun have a different fate • Sun does NOT!!!!! “go supernova” Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Main Sequence to Red Giant • After the core becomes depleted of H, the Sun will become a red giant • • He core H burning shell A much larger, cooler star Ar#sts concept of the Sun as a red giant: Image: ESA Earth, in all likelihood, gets swallowed up Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Red Giant to White Dwarf Spitzer Space Telescope Image of a PN the Helix Nebula • Eventually the red giant exhausts the H in its shell • throws off up to half its mass • “planetary nebula” Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Fading away... • Core becomes a white dwarf • Squeezed into size of Earth • Maximally compressed into a degenerate gas • In isolation, very slowly cools and fade away Astronomy 1 - Elementary Astronomy Artist’s concept Image ESA/NASA LA Mission College Levine F2015 Let’s Practice The Sun will ultimately A. Go Supernova B. Become a white dwarf C. Become a black hole Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Which of the following are the most potentially damaging consequences of solar activity A. Solar flares & Aurora Borealis B. Coronal Mass Ejections & Geomagnetic storms C. Promenences and Spicules Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The Earth as a Planet Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Comparison of the “Terrestrial” Planets Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The “Habitable Zone” www.astrobio.net • In astronomy and astrobiology, the habitable zone is the region around a star where a planet with sufficient atmospheric pressure can maintain liquid water on its surface. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Earth’s Statistics • • • • • • • Equatorial Diameter = 12,756 km Mass = 5.98 x 1024 kg av. density = 5.5 g/cc surface T = -50°C to +50°C a = 1.00 AU P = 1.00 year e = 0.0167 Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Earth’s Uniqueness • Every major process on any rocky world in our solar system is represented in some form on Earth. • Unique in 2 important ways 1. Surface water (75% of the surface is water) • No other SS body has surface water currently 2. Life • No other SS body has been found to have life. Yet. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Earth’s Early History • Formed 4.6 billion years (4.6 x 109) ago from the inner solar nebula. • 4 Stages of Evolution: • • Differentiation • • Flooding Heavy Bombardment: Cratering Slow Surface Evolution Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Earth’s Structure — Core • • • • Hot as the Sun’s surface (~6000 K) Solid inner core liquid core surrounding it Source of Earth’s magnetic field • Dynamo effect Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Earth’s Structure — Mantle • Solid (“plastic”) Mantle • As in deformable, not as in manmade Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Earth’s Structure — Crust • Solid • • • Thicker under land (60 km) thinner under oceans (10 km) Brittle: Broken into tectonic plates • only terrestrial planet with plate tectonics Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Earth’s Magnetic Field • Is Useful • • • Likely helps birds & fish know where N and S are for migration Compasses Most importantly, it protects us from the solar wind • • which would otherwise slowly strip the Earth’s atmosphere away...which would NOT be good! Is generated by the dynamo effect Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Magnetic Field via Dynamo Effect • 2 Key components • • • Liquid conductor Rotation Earth • ample liquid iron outer core, plus • fairly brisk 24 hr rotation, yields • strong magnetic field Astronomy 1 - Elementary Astronomy image from: http://www.abc.net.au LA Mission College Levine F2015 The Core and the Dynamo • Earth’s core consists mostly of iron + nickel • • high electrical conductivity. A conductor in motion creates a magnetic field • The liquid core convects and the Earth Rotates • Results in a dipole field Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 PLATE TECTONICS Plate Tectonics • Plates are moved by convective motion in the mantle • hot material rises and cools, cool material sinks Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Earth’s Tectonic History Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 LET’S PRACTICE If the Earth’s rotation were to slow down drastically which of the following would most likely happen? A. Runaway Greenhouse effect, leading to unsurvivable surface temperatures B. Diminishment of Earth’s magnetic field, leading to loss of protection from the solar wind C. Diminishment of atmospheric friction, leading to dramatic cooling of the surface D. Diminishment of gravitational force, leading to loss of the Moon. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Plate tectonics exists on Earth because _____. A. convection in the mantle causes motion B. the crust is thin and broken into pieces C. both of these D. neither of these Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 EARTH’S TIMELINE History of Geological Activity Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Earth’s Atmosphere • 76% Nitrogen, 23% Oxygen, 1.3% Argon & a smattering of other stuff • • • (water and carbon dioxide included). Ozone (O3) protects the surface from UV radiation (26 km up). Carbon Dioxide i s a “greenhouse gas:” it is transparent to visible light, but opaque to infrared light Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Evolution of Atmosphere • • Primordial Atmosphere • Whatever was outgassed by the geologic activity (volcanoes) of ~4 billions years ago. • carbon dioxide (CO2), nitrogen, water vapor. The CO2 levels decreased • • As Earth cooled, water vapor condensed. Oceans formed! • The CO2 reacted with other elements in the water The oceans absorbed CO2 (CO2 is soluble in water… think carbonated drinks!) Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Evolution of Atmosphere • O2 levels increased • Initially, any oxygen present reacted with minerals to form iron oxide, etc… • The rise of oxygen levels in the Earth’s atmosphere is tied to life. • Specifically photosynthesis • • • evolved 2.7 - 2.4 billion years ago picked up when the oceans developed plant life 2-2.5 billion years ago Oxygen exists because of life, not vice versa! Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Where Water Came From • • Not completely well understood. Several hypotheses: Older hypothesis: Primordial content and Vulcanism • • • When a volcano erupts, 50-80 % of the gas is water vapor. Newer understanding: Primordial outgassing • Earth formed so rapidly that it was substantially heated by the impacts of infalling material, as well as by radioactive decay. • • Molten surface -> continuous outgassing straight to the volcanic “ secondary atmosphere” without a hydrogen- rich primeval atmosphere. Some of the water may have arrived late in the formation as a bombardment of volatile-rich planetesimals • studies of Comet LINEAR, which broke up in 1999 as it passed near the sun, support this Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The Moon The Moon Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Importance of the Moon • Galileo Image taken on way to Outer Solar System Moderates wobble of Earth’s axis • stabilizes climate • • Tides • Only place aside from Earth we have visited in person • Lunar Ranging Image Credit: NASA Cultural and Historical importance Apollo 16, Image Credit: NASA Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 CHARACTERISTICS OF THE MOON Moon • • • • Equatorial Diameter = 3476 km • mass = 7.35 x 1022 kg average density = 3.4 g/cc surface temp = -170°oC to +130°C • • • Earth a = 384,400 km (from Earth!) P = 29.5 days (around Earth!) e = 0.055 Astronomy 1 - Elementary Astronomy • • • • • • Equatorial Diameter = 12,756 km mass = 5.98 x 1024 kg average density = 5.5 g/cc surface temp = -50°C to +50°C a = 1.00 AU P = 1.00 y e = 0.0167 LA Mission College Levine F2015 Key Characteristics of the Moon Credit: NASA/GSFC/Arizona State University Oblique View of the Lunar Crater Tycho • No magnetic field • • No atmosphere • • • Small core, no iron Too small & hot to hold onto gases gas molecules readily reach escape velocity! Very dry • • no sedimentary rock some ice may exist under the surface Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The Moon: The View from Earth • Tidally coupled to the earth • • rotation = revolution always see same side • Heavily cratered highlands • Smoother, darker lowlands • • • Farside from Nearside fromLRO LRO maria (“seas”) Credit: NASA/ GSFC/Arizona State University flooded by lava Cool Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Lunar Craters • Numerous! • >300,000 • Named after people: scholars, scientists, explorers • Typical crater morphology Astronomy 1 - Elementary Astronomy Plato Mare Imbrium Aristarchus Oceanus Kepler Procellarum Mare Serenitatis Copernicus Mare Tranquillitatis Mare Crisium Mare Nubium Tycho LA Mission College Levine F2015 Lunar Maria • large, dark, basaltic plains • • • lava flooded low-lying areas more prevalent on near side Plato Mare Imbrium Aristarchus Oceanus Kepler Procellarum Mare Serenitatis Copernicus Mare Tranquillitatis Mare Crisium Mare Nubium 1.2-4.2 billion y.o. • • Tycho radiometric dating crater counting Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 LET’S PRACTICE There is very little atmosphere on the Moon because A. dry rocks on the moon absorb gases as soon as they are created. B. it was blown away by meteor bombardment. C. its low mass and high temperature allowed most gases to escape. D. the gravitational tidal forces from the Earth stripped it away. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The Moon A. always points the same face towards the Sun. B. does not rotate. C. rotates at the same rate as the Earth rotates -once per day. D. rotates at the same rate as it revolves around Earth -- once per month. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 LUNAR EXPLORATION History of Lunar Exploration • • 1st visited by the USSR's Luna 1 and Luna 2 in 1959. These were followed by a number of U.S. and Soviet robotic spacecraft. US sent: • • • • • Rangers (1961-1965) were impact probes, Lunar Orbiters (1966-1967) mapped the surface Surveyors (1966-1968) were soft landers. Apollo program -- Men on the Moon Lunar exploration resumed in the 1990s • Clementine & Lunar Prospector Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Manned Lunar Exploration • May 25, 1961 -- President John Kennedy committed the United States to landing a human being on the moon by 1970. • Vehicle hefty enough to get to moon would be difficult to land: Two-module design with “disposable” lander • • • • Command module The lunar landing module ( LM ) The first human- piloted lunar landing was made July 20, 1969. July 1969 -- December 1972,: • • 12 people reached the lunar surface collected 380 kg ( 840 lb) of rocks and soil Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Apollo Landing Sites • First Apollo missions landed on safe, smooth terrain. • • Apollo 11: Mare Tranquilitatis; lunar lowlands Later missions explored more varied terrains. • Apollo 17: TaurusLittrow; lunar highlands Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The Apollo Missions • Hoax Believers, please check out Mr. “Bad Astronomy” Phil Platt’s extensive rebuttal: • • http://www.badastronomy.com/bad/tv/foxapollo.html And this filmmaker’s assessment of why faking it would have been harder than making it • http://www.space.com/19531-moon-landings-faked-filmmaker-says-not-video.html Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Moon Landing Remastered • http://video.nationalgeographic.com/video/news/spacetechnology-news/1969-moonlanding-vin/ Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Moon Rocks Vesicular (= containing holes from gas bubbles in the lava) basalts, typical of dark rocks found in maria • Breccias (= fragments of different types of rock cemented together), also containing anorthosites (= bright, low-density rocks typical of highlands) Older rocks become pitted with small micrometeorite craters. Igneous (solidified lava) • No sedimentary rock Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 LUNAR FORMATION Must Explain • • • • • • Similar oxygen isotopic composition to Earth But different chemical composition -- low density No magnetic field All igneous rock Same age as Earth Maria and Highlands Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Moon formation • Fission Hypothesis • • Condensation Hypothesis • • Earth & Moon formed as a double planet system Capture Hypothesis • • Earth broke in two (if it were spinning quickly enough) Earth gravitationally captured a pre-existing body Large-impact hypothesis • Early earth and moon formed from the glancing collision of two protoplanets • Resulting large body became the earth and ejected debris formed the moon • Could have caused Earth’s 23° tilt Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Large Impact Hypothesis • • Impacting body about the size of Mars — Theia Impact heated material enough to melt it • • Collision not head-on • • consistent with “sea of magma” Large angular momentum of Earth-moon system Collision after differentiation of Earth’s interior • • • Different chemical compositions of Earth and moon Earth absorbed iron core of impactor Molten remnant material coalesced into Moon Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 LET’S PRACTICE Which proposed explanation for the Moon’s origin was ruled out when the Apollo mission revealed similar abundances of isotopes of oxygen in lunar rock as on Earth? A. that the Moon broke off from the Earth B. that the Moon and Earth formed together out of the same material C. that the Moon was a passing body that was gravitationally captured by the Earth D. that the Moon was formed when a large object impacted the proto-Earth Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 WRAP-UP Topic for Next Class • • Mercury, Venus, Mars Greenhouse effect Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Reading Assignment • • Astro: 7 Astropedia: 8 Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Homework • No new HW yet Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015