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Midterm Review, Greenhouse LT, Small Bodies Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Quotes & Cartoon of the Day “I have just gone over my comet computations again, and it is humiliating to perceive how very little more I know than I did seven years ago when I first did this kind of work.” -- Maria Mitchell Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Announcements • • • Midterm Thursday Have you selected your observing proposal yet? Reordering topics so as to be properly up to date on Mars, Pluto and Enceladus! Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Last Class • Brief Backtrack • • • • SS Formation Earth in brief LT Greenhouse Effect Climate Change Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 This Class • • Midterm Review Greenhouse Effect • • • LT Greenhouse Effect Climate Change If Time: • • • • Meteor/oid/ite Asteroids Comets Kuiper Belt Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 OLD DEAD GUYS Greeks to Kepler • • • • Greek ideas Copernican Revolution Tycho Brahe Kepler the dude Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Kepler’s 3 laws of Planetary Motion 1. The orbits of the planets are ellipses, with the Sun at one focus. 2. A line from a planet to the Sun sweeps out equal areas in equal periods of time • Planets move fastest when physically closest to the Sun, and slowest when farthest. 3. A planet’s orbital period squared, is proportional to it’s farthest distance from the Sun cubed: • P2 = a3 Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Kepler to Sir Issac • • Galileo Sir Issac • • Contributions and fields of study Law of Universal Gravity Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Law of Universal Gravity • Be able to explain how the force varies (larger or smaller) with mass of either object, both objects and distance • Be able to work the inverse square relationship -- how does force change if distance doubles.... Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 LIGHT, OPTICS, TELESCOPES Nature of Light • • • • • Why this is important for Astronomy electromagnetic radiation waves, particles, duality all light, from radio to gamma ray is same thing all light travels at the same speed in vacuum • c=3x108 m/s Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Properties of Light • Waves • • • • λ = c/f Interference Particles • • • • Relationship of wavelength and frequency Photoelectric effect E = h f = hc/λ h = 6.6 x 10-34 Js = 6.6 x 10-34 J/Hz Know what these relationships mean (i.e the ranking exercise from HW) Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Electromagnetic Spectrum • • • difference between red and blue light Basic bands of EMR (e.g. radio, visible, IR etc.) Relationship between band, wavelength & Energy Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Telescopes and Observatories • • • • Refractors and Reflectors Size (of primary) matters Atmospheric Transmission Multiwavelength Astronomy • What are IR and Radio good for? Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 SOLAR SYSTEM Solar System Properties • Overall “bulk” properties • • • • Disk shape two types of planets Space “debris” common age Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Solar System Properties • “Anatomy” What and Where • • • • • • • • Sun Inner SS & terrestrial planets Asteroid Belt Outer SS & Jovian planets Kuiper Belt Heliopause Oort cloud Size/Distance Scales Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Solar System Formation • • • • • • • Raw materials -- big bang, role of supernovae Solar Nebula Theory Differentiation Frost line Planet formation -- both types Disk clearing Cratering & Craters Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Greenhouse Effect Recap Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Greenhouse Effect • Glass: • • • transparent to visible light opaque to IR light Greenhouse • visible light enters through glass • • • warms ground & air • Greenhouse gets warmer than outside ground & air give off IR IR can’t exit through glass Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Greenhouse Gasses • Carbon dioxide & other gasses • • transparent to visible light absorb IR light Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 WARMUP QUESTION Which of the following is part of the Earth’s natural greenhouse effect? A. Earth’s atmosphere continually becomes thicker with greenhouse gases. B. Infrared light becomes permanently trapped in our atmosphere by greenhouse gases. C. The ozone hole causes significant increases in surface temperature. D. Earth’s surface and atmospheric gases absorb energy and then give off infrared light. E. Heat is transferred in the atmosphere through the circulation of greenhouse gases. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 LECTURE-TUTORIAL GREENHOUSE EFFECT Which of the following is part of the Earth’s natural greenhouse effect? A. Earth’s atmosphere continually becomes thicker with greenhouse gases. B. Infrared light becomes permanently trapped in our atmosphere by greenhouse gases. C. The ozone hole causes significant increases in surface temperature. D. Earth’s surface and atmospheric gases absorb energy and then give off infrared light. E. Heat is transferred in the atmosphere through the circulation of greenhouse gases. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Let’s Practice If Earth’s atmosphere were able to completely absorb visible light, which of the following would be true? A. The Earth’s surface temperature would be cooler than it is today. B. The Earth’s surface temperature would be warmer than it is today. C. The Earth’s surface temperature would be the same temperature as it is today. D. There is not enough information to answer this question. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 HUMANS AND CLIMATE CHANGE Greenhouse Effect • • • • Is a natural process Essential to maintain Earth’s temperature HOWEVER Human activity has dramatically increased the level of greenhouse gasses • Esp. via the internal combustion engine Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Global Warming NASA Goddard Institute for Space Studies • Beyond any reasonable doubt, the average temperature on Earth is increasing. • • • loss of glaciers & polar ice caps rising sea water levels global climate change Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 ICE MELT (TIME PERMITTING) TED Talk, Jun 2009 Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Small Solar System Bodies Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Meteors -ites, -oids Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 “Meteor…” • Meteor -- The flash of light you see in the sky when a space rock is heated to incandescence due to atmospheric friction. • Meteorite -- the rock, once it lands on Earth (if it is big enough to make it intact, through the atmosphere) • • Meteoroid -- the rock, while still in space Meteor Shower --When lots of meteors are seen in the sky • • 80 - 100 per hour is a good showing! Caused when the Earth, on it’s trip around the Sun, passes through a cloud of space dust/rock. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Meteorites • • Sizes from microscopic dust to a few centimeters • Statistically, one meteorite is expected to strike a building somewhere on Earth every 16 months. • Typically impact onto the atmosphere with 10 – 30 km/s (≈ 30 times faster than a rifle bullet) • Can come from various sources About 2 meteorites, large enough to produce visible impacts, strike the Earth every day. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Meteor Showers • Earth passing through area of debris Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Let’s Practice Which of the following could cause a meteor shower? A. A meteoroid hits a cloud in the atmosphere and causes a thunderstorm. B. The Earth crosses the debris-filled orbit of a comet. C. Asteroids in the same orbit as the Earth. D. A small constellation of dying stars disintegrates. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Asteroids Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Asteroids • Small rocky bodies that orbit the Sun. • Millions orbit the Sun between the orbits of Mars and Jupiter -- the asteroid belt • • Most are potato shaped (not round). Most have craters. • Last remains of planetesimals that built the planets 4.6 billion years ago! • Can be stony (like Earth’s crust) or iron (like Earth’s Core). • The largest body in the asteroid belt (Ceres) is now classified as a dwarf planet. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Asteroid - Earth Collisions http://www.hooked-nussu.org/images/stories/issue/armageddon.jpg • • Not a good thing • Tunguska: June 30th 1908 Yucatan 65 million years ago Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Asteroid - Earth Collisions http://www.soundtrackcollector.com/catalog/soundtrackdetail.php?movieid=9365 • • Not a good thing • Tunguska: June 30th 1908 Yucatan 65 million years ago Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Asteroid - Earth Collisions http://astro.wsu.edu/worthey/astro/html/im-meteor/ tunguska.html • • Not a good thing Tunguska: June 30th 1908 Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Comets Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Comets • Throughout history, Comet McNaught in 2007 comets have been considered as portents of doom, even very recently: • Appearances of comet Kohoutek (1973), Halley (1986), and Hale-Bopp (1997) caused great concern among the superstitious. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Comets http://thegalaxyguide.com/galaxy/ • Objects of ice/rock/dust orbiting the Sun, with highly elliptical orbits. • At perihelion (closest point to the Sun), a coma and a tail typically appear due to the increased solar radiation Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Comets: two types of tails • Ion tail • • Ionized gas pushed away from the comet by the solar wind Pointing straight away from the sun Dust tail • Dust set free from vaporizing ice in the comet; carried away from the comet by the sun’s radiation pressure. Lagging behind the comet along its trajectory Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Comet Nuclei • Comet nuclei contain ices of water, carbon dioxide, methane, ammonia, etc.: • Those compounds sublime (transition from solid directly to gas phase) as comets approach the sun.. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Short Period Comets • • orbital periods of less than 200 years • short-period comets are thought to originate from the centaurs and the Kuiper belt/scattered disc more-or-less in the ecliptic plane in the same direction as the planets Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Long Period Comets • periods ranging from 200 years to thousands or even millions of years. • • • • highly eccentric orbits orbits take them far beyond the outer planets plane of their orbits need not lie near the ecliptic. Believed to come from the Oort Cloud Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Let’s Practice The orbits of long period comets are ___. A. identical to the orbits of short period comets B. nearly circular C. exactly in the same plane as the planets D. randomly oriented with respect to the orbits of the planets E. more than one of the above Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The fact that short period comets have short periods compared to long period comets implies that shortperiod comets _____ than long-period comets. A. originate from a place closer to the Sun B. have a different composition C. are less massive D. are smaller in diameter E. have shorter tails Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 The tail of a comet is generally directed _______. A. toward the Sun because of its gravitational attraction B. away from the Sun because of radiation pressure and the solar wind C. opposite to the direction of motion because of interaction with interplanetary matter D. along the comet’s magnetic field lines Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 A distant comet at its farthest point from the Sun would have which of the following? A. Dust tail B. Ion tail C. Nucleus D. Coma Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Kuiper Belt Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 The Kuiper Belt • ~ 30 – 100 AU from the sun. • 2nd source of small, icy bodies in the outer solar system • After passing Pluto, the New Horizons spacecraft is planned to fly past at least one Kuiper Belt object. Astronomy 1 - Elementary Astronomy NASA LA Mission College Levine F2015 Oort Cloud Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Origin of Comets • • Long Period comets are believed to originate in the Oort cloud Spherical cloud of several trillion icy bodies, ~ 10,000 – 100,000 AU from the sun Astronomy 1 - Elementary Astronomy 10,000 – 100,000 AU Oort Cloud LA Mission College Levine F2015 Origin of Comets • • Gravitational influence of occasional passing stars may perturb some orbits and draw them towards the inner solar system. 10,000 – 100,000 Interactions with planets may perturb orbits further, capturing comets in short-period orbits. Astronomy 1 - Elementary Astronomy AU Oort Cloud LA Mission College Levine F2015 Let’s Practice Short-period comets are associated with what class of objects? A. Kuiper Belt objects B. Terrestrial planets C. The Oort Cloud D. The giant planets Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 What property of the Oort cloud is consistent with long-period comets having orbits that are oriented randomly with respect to the ecliptic? A. It is very far from the Sun B. It contains small icy bodies C. It may interact with other stars D. It is spherical Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 WRAP-UP Topic for Next Class • Midterm Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Reading Assignment • Read up on Mars for Tuesday Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Homework • No new HW yet Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015