DOCSLIB.ORG

05 the Earth, Moon, and Sky.Pdf

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
05 the Earth, Moon, and Sky.Pdf The Earth, Moon, and Sky Lecture 5 1/31/2017 From Last Time: Stable Orbits • The type of orbit depends on the initial speed of the object • Stable orbits are either circular or elliptical. • Too slow and gravity pulls the object back in • Too fast and gravity is not strong enough. This is called the escape velocity From Last Time: Difference between Mass and Weight • Newton’s Second Law: Force = mass x acceleration • Mass is a measure of how much material an object has. • Weight (force) is a measure of home much acceleration a mass is feeling. • Earth’s surface acceleration 9.8 m/sec2 -> • My weight is 889 Newtons (mass = 90.7 Kg) • Jupiter’s surface acceleration 24.79 m/sec2 -> • My weight is 2248.4 Newtons • We as a society conflate mass and weight since everyone feels the same gravity. We mix up Newtons and Kilograms, though not the same. Locating Places on Earth • We live on a sphere and thus define our position using two angles. • Latitude measures North/South angular distances with 0 degrees at the Equator • Longitude measures East/West angular distances with 0 degrees on the Prime Meridian (Greenwich, England). • Washington, DC is at 38.9072° N, 77.0369° W • Albuquerque is at 35.0853° N, 106.6056° W • Melbourne Australia is at 37.8136° S, 144.9631° E The Seasons • The Earth is on an elliptical orbit, sometimes it is farther away to Sun, sometimes it is closer. Does this create Seasons? • It is summer in the southern hemisphere. • Earth is actually its closest to the Sun in January. • Earth varies its distance to the Sun by about 3% over a year. • Conclusion: Earth changing its distance to the Sun create seasons. • Axial tilt, 23.5o, does create seasons. • The Suns position in the sky changes throughout the year because of the tilt Axial Tilt: 23.5o • Summer occurs for a certain hemisphere, when it is “leaning” towards the Sun. • Hemispheres distance to the Sun is changing, but it is insignificant relative to the distance from the Sun to the Earth. • Sun light is more direct in Summer and more spread out in Winter. Summer Winter Seasons also depend of the amount of daylight. Solstices • Around June 21, the Sun is the most over head it will be all year. • At Latitude 23.50 N, Tropic of Cancer, the Sun appears directly overhead at noon. • 90° – 23° (or 67° N), Article Circle, the Sun does not set that day. Equinoctia • Halfway between the solstices, on about March 21 and September 21. • The Sun is on the celestial equator and whole planet receives ~12 hours day/night • At the poles of the Earth, the Sun only rises or sets once per year on the equinox. Length of the Day • A day is a measure of how long the Earth takes to rotate relative to… • Relative to the Sun: Solar Day (24 hours) • Relative to distance stars: Sidereal Day (23 hours 56 minutes) Now: Scorpius Night Day Day Night Orion Summer: July Winter: January 13,000 years from now: Scorpius Night Day Day Night Orion Winter: July or January? Summer: January or July? We choose to keep July a summer month, but then in 13,000 years, summer occurs on other side of orbit! The Year Summer Winter Sun low in Night Day Sun high in Day Night northern sky northern sky • The Earth revolves around the Sun in 365.256 days (“sidereal year”). But the year we use is 365.242 days (“tropical year”). Why? • Why do we have a leap year? The Motion of the Moon • Half of the Moon's surface is lit by the Sun. • The Moon has a cycle of "phases", which lasts about 29 days. • During this cycle, we see different fractions of the sunlit side. Which way is the Sun here? Cycle of phases slightly longer than time it takes Moon to do a complete orbit around Earth. Cycle of phases or Orbit time or "synodic month” "sidereal month” 29.5 days 27.3 days Tides • A feature of oceans (but solid materials have small tides too). • Two high and two low tides per day. • Tides are due to the gravitational pull being stronger on side of Earth closest to it (Sun causes smaller tides) • Earth-Moon gravity keeps them orbiting each other. But side of Earth closest to Moon has slightly stronger pull to Moon => bulges towards it. • Other side has weaker pull => bulges away compared to rest of Earth. • The Earth spins once a day while the bulge always points towards and away from the Moon => high and low tides. Eclipses Lunar eclipse: When the Earth passes directly between the Sun and the Moon. Earth Moon Sun Solar eclipse: When the Moon passes directly between the Sun and the Earth. Moon Earth Sun Moon's orbit tilted compared to Earth-Sun orbital plane: Sun Moon Earth 5.2o Side view Moon's orbit slightly elliptical: Moon Distance varies by ~14% Earth Top view, exaggerated ellipse .
Load more

Recommended publications
  • Current State of Knowledge of the Magnetospheres of Uranus and Neptune
    Current State of Knowledge of the Magnetospheres of Uranus and Neptune 28 July 2014 Abigail Rymer [email protected] What does a ‘normal’ magnetosphere look like? . N-S dipole field perpendicular to SW . Solar wind driven circulation system . Well defined central tail plasmasheet . Loaded flux tubes lost via substorm activity . Trapped radiation on closed (dipolar) field lines close to the planet. …but then what is normal…. Mercury Not entirely at the mercy of the solar wind after all . Jupiter . More like its own little solar system . Sub-storm activity maybe totally internally driven …but then what is normal…. Saturn Krimigis et al., 2007 What is an ice giant (as distinct from a gas giant) planet? Consequenses for the magnetic field Soderlund et al., 2012 Consequenses for the magnetic field Herbert et al., 2009 Are Neptune and Uranus the same? URANUS NEPTUNE Equatorial radius 25 559 km 24 622 km Mass 14.5 ME 17.14 ME Sidereal spin period 17h12m36s (retrograde) 16h6m36s Obliquity (axial tilt to ecliptic) -97.77º 28.32 Semi-major axis 19.2 AU 30.1 AU Orbital period 84.3 Earth years 164.8 Earth years Dipole moment 50 ME 25 ME Magnetic field Highly complex with a surface Highly complex with a surface field up to 110 000 nT field up to 60 000 nT Dipole tilt -59º -47 Natural satellites 27 (9 irregular) 14 (inc Triton at 14.4 RN) Spacecraft at Uranus and Neptune – Voyager 2 Voyager 2 observations - Uranus Stone et al., 1986 Voyager 2 observations - Uranus Voyager 2 made excellent plasma measurements with PLS, a Faraday cup type instrument.
    [Show full text]
  • Solar Illumination Conditions at 4 Vesta: Predictions Using the Digital Elevation Model Derived from Hst Images
    42nd Lunar and Planetary Science Conference (2011) 2506.pdf SOLAR ILLUMINATION CONDITIONS AT 4 VESTA: PREDICTIONS USING THE DIGITAL ELEVATION MODEL DERIVED FROM HST IMAGES. T. J. Stubbs 1,2,3 and Y. Wang 1,2,3 , 1Goddard Earth Science and Technology Center, University of Maryland, Baltimore County, Baltimore, MD, USA, 2NASA Goddard Space Flight Center, Greenbelt, MD, USA, 3NASA Lunar Science Institute, Ames Research Center, Moffett Field, CA, USA. Corresponding email address: Timothy.J.Stubbs[at]NASA.gov . Introduction: As with other airless bodies in the plane), the longitude of the ascending node is 103.91° Solar System, the surface of 4 Vesta is directly exposed and the argument of perihelion is 149.83°. Based on to the full solar spectrum. The degree of solar illumina- current estimates, Vesta’s orbital plane is believed to tion plays a major role in processes at the surface, in- have a precession period of 81,730 years [6]. cluding heating (surface temperature), space weather- For the shape of Vesta we use the 5 × 5° DEM ing, surface charging, surface chemistry, and exo- based on HST images [5], which is publicly available spheric production via photon-stimulated desorption. from the Planetary Data System (PDS). To our knowl- The characterization of these processes is important for edge, this is the best DEM of Vesta currently available. interepreting various surface properties. It is likely that The orbital information for Vesta is obtained from the solar illumination also controls the transport and depo- Dawn SPICE kernel, which currently limits us to the sition of volatiles at Vesta, as has been proposed at the current epoch (1900 to present).
    [Show full text]
  • Our Solar System
    This graphic of the solar system was made using real images of the planets and comet Hale-Bopp. It is not to scale! To show a scale model of the solar system with the Sun being 1cm would require about 64 meters of paper! Image credit: Maggie Mosetti, NASA This book was produced to commemorate the Year of the Solar System (2011-2013, a martian year), initiated by NASA. See http://solarsystem.nasa.gov/yss. Many images and captions have been adapted from NASA’s “From Earth to the Solar System” (FETTSS) image collection. See http://fettss.arc.nasa.gov/. Additional imagery and captions compiled by Deborah Scherrer, Stanford University, California, USA. Special thanks to the people of Suntrek (www.suntrek.org,) who helped with the final editing and allowed me to use Alphonse Sterling’s awesome photograph of a solar eclipse! Cover Images: Solar System: NASA/JPL; YSS logo: NASA; Sun: Venus Transit from NASA SDO/AIA © 2013-2020 Stanford University; permission given to use for educational and non-commericial purposes. Table of Contents Why Is the Sun Green and Mars Blue? ............................................................................... 4 Our Sun – Source of Life ..................................................................................................... 5 Solar Activity ................................................................................................................... 6 Space Weather ................................................................................................................. 9 Mercury
    [Show full text]
  • Effects of the Moon on the Earth in the Past, Present, and Future
    Effects of the Moon on the Earth in the Past, Present, and Future Rina Rast*, Sarah Finney, Lucas Cheng, Joland Schmidt, Kessa Gerein, & Alexandra Miller† Abstract The Moon has fascinated human civilization for millennia. Exploration of the lunar surface played a pioneering role in space exploration, epitomizing the heights to which modern science could bring mankind. In the decades since then, human interest in the Moon has dwindled. Despite this fact, the Moon continues to affect the Earth in ways that seldom receive adequate recognition. This paper examines the ways in which our natural satellite is responsible for the tides, and also produces a stabilizing effect on Earth’s rotational axis. In addition, phenomena such as lunar phases, eclipses and lunar libration will be explained. While investigating the Moon’s effects on the Earth in the past and present, it is hoped that human interest in it will be revitalized as it continues to shape life on our blue planet. Keywords: Moon, Earth, tides, Earth’s axis, lunar phases, eclipses, seasons, lunar libration Introduction lunar phases, eclipses and libration. In recognizing and propagating these effects, the goal of this study is to rekindle the fascination humans once held for the Moon Decades have come and gone since humans’ fascination and space exploration in general. with the Moon galvanized exploration of the galaxy and observation of distant stars. During the Space Race of the 1950s and 1960s, nations strived and succeeded in reaching Four Prominent Lunar Effects on Earth Earth’s natural satellite to propel mankind to new heights. Although this interest has dwindled and humans have Effect on Oceans and Tides largely distanced themselves from the Moon’s relevance, its effects on Earth remain as far-reaching as ever.
    [Show full text]
  • On the Irrelevance of Being a PLUTO! Size Scale of Stars and Planets
    On the irrelevance of being a PLUTO! Mayank Vahia DAA, TIFR Irrelevance of being Pluto 1 Size Scale of Stars and Planets Irrelevance of being Pluto 2 1 1 AU 700 Dsun Irrelevance of being Pluto 3 16 Dsun Irrelevance of being Pluto 4 2 Solar System 109 DEarth Irrelevance of being Pluto 5 11 DEarth Venus Irrelevance of being Pluto 6 3 Irrelevance of being Pluto 7 Solar System visible to unaided eye Irrelevance of being Pluto 8 4 Solar System at the beginning of 20 th Century Irrelevance of being Pluto 9 Solar System of my text book (30 years ago) Irrelevance of being Pluto 10 5 Asteroid Belt (Discovered in 1977) Irrelevance of being Pluto 11 The ‘Planet’ Pluto • Pluto is a 14 th magnitude object. • It is NOT visible to naked eye (neither are Uranus and Neptune). • It was discovered by American astronomer Clyde Tombaugh in 1930. Irrelevance of being Pluto 12 6 Prediction of Pluto • Percival Lowell and William H. Pickering are credited with the theoretical work on Pluto’s orbit done in 1909 based on data of Neptune’s orbital changes. • Venkatesh Ketakar had predicted it in May 1911 issue of Bulletin of the Astronomical Society of France. • He modelled his computations after those of Pierre-Simon Laplace who had analysed the motions of the satellites of Jupiter. • His location was within 1 o of its correct location. • He had predicted ts orbital period was 242.28 (248) years and a distance of 38.95 (39.53) A.U. • He had also predicted another planet at 59.573 A.U.
    [Show full text]
  • Retrograde-Rotating Exoplanets Experience Obliquity Excitations in an Eccentricity- Enabled Resonance
    The Planetary Science Journal, 1:8 (15pp), 2020 June https://doi.org/10.3847/PSJ/ab8198 © 2020. The Author(s). Published by the American Astronomical Society. Retrograde-rotating Exoplanets Experience Obliquity Excitations in an Eccentricity- enabled Resonance Steven M. Kreyche1 , Jason W. Barnes1 , Billy L. Quarles2 , Jack J. Lissauer3 , John E. Chambers4, and Matthew M. Hedman1 1 Department of Physics, University of Idaho, Moscow, ID, USA; [email protected] 2 Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA, USA 3 Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, CA, USA 4 Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC, USA Received 2019 December 2; revised 2020 February 28; accepted 2020 March 18; published 2020 April 14 Abstract Previous studies have shown that planets that rotate retrograde (backward with respect to their orbital motion) generally experience less severe obliquity variations than those that rotate prograde (the same direction as their orbital motion). Here, we examine retrograde-rotating planets on eccentric orbits and find a previously unknown secular spin–orbit resonance that can drive significant obliquity variations. This resonance occurs when the frequency of the planet’s rotation axis precession becomes commensurate with an orbital eigenfrequency of the planetary system. The planet’s eccentricity enables a participating orbital frequency through an interaction in which the apsidal precession of the planet’s orbit causes a cyclic nutation of the planet’s orbital angular momentum vector. The resulting orbital frequency follows the relationship f =-W2v , where v and W are the rates of the planet’s changing longitude of periapsis and longitude of ascending node, respectively.
    [Show full text]
  • Lunar Polar Ice and the Obliquity History of the Moon
    EPSC Abstracts Vol. 6, EPSC-DPS2011-1615, 2011 EPSC-DPS Joint Meeting 2011 c Author(s) 2011 Lunar Polar Ice and the Obliquity History of the Moon M.A. Siegler (1), B.G. Bills2 (2) and D.A. Paige (1) (1)UCLA Dept. of Earth and Planetary Sciences, Los Angeles, CA, 90095, (2)NASA Jet Propulsion Laboratory, Pasadena, CA, 91109 ([email protected]) Abstract sis [1] of these orbital models combines these orbital parameters to create a history of the axial tilt (maxi- Water ice is currently stable from sublimation loss mum yearly sun angle) as seen in Figure 1. in shadowed environments near the lunar poles. However, most current temperature environments are generally too cold to allow efficient diffusive migra- tion into the subsurface by that would protect water from non-sublimation loss. This has not always the case. Higher past lunar obliquities caused currently shadowed polar regions to have warmer thermal envi- ronments. These past environments may have been both cold enough to be able to capture surface ice, but warm enough to drive it into the subsurface. Figure 1: Axial tilt (with respect to the ecliptic) history of the Moon. The large increase at approximately 30 RE semimajor 1. Lunar Orbit History axis is a result of a transition between two Cassini States. The current tilt is roughly 1.54o. Roughly halfway through its outward migration (due to tidal interaction with the Earth) the Moon was 2. Thermal Model tilted (currently 1.54o) up to 83o with respect to the ecliptic. During this time, all polar craters would ful- Next, we examine the thermal environments re- ly illuminated at some point in the year and have sulting from the slow orbital evolution since the Cas- been far too warm to preserve water ice [1].
    [Show full text]
  • A PRE-DAWN PERSPECTIVE — VESTA and the Heds 6:00 P.M
    42nd Lunar and Planetary Science Conference (2011) sess605.pdf Thursday, March 10, 2011 POSTER SESSION II: A PRE-DAWN PERSPECTIVE — VESTA AND THE HEDs 6:00 p.m. Town Center Exhibit Area Wilson L. Keil K. McCoy T. Explosive Volcanism on Asteroids Re-Visited: Sizes of Pyroclasts Lost or Retained [#1362] We calculate the sizes expected for pyroclasts from explosive eruptions on large and small asteroids and specify the sizes of clasts that should be retained on the asteroid surfaces. Hammergren M. Gyuk G. Solontoi M. Puckett A. W. Basaltic Asteroids in the Middle and Outer Main Belt Observed by the AVAST Survey [#2821] We present the preliminary results of reflectance spectroscopy of basaltic asteroids obtained in the Adler V-Type Asteroid (AVAST) survey. In particular, we note several basaltic asteroids in the middle and outer main belt, including 105041 (2000 KO41) and 63085. Raymond C. A. Russell C. T. Rayman M. D. Mase R. A. Dawn Team Dawn’s Exploration of Vesta [#2730] The Dawn spacecraft will reach Vesta in mid-2011 and begin a comprehensive geological and geophysical characterization to investigate the geologic history, interior structure, and evolution of this minor planet in the main asteroid belt. Jaumann R. Pieters C. M. Neukum G. Mottola S. DeSanctis M. C. Russell C. T. Raymond C. A. McSween H. Y. Roatsch T. Nathues A. Preusker F. Scholten F. Blewett D. Buczkowski D. L. Hiesinger H. McCord T. Rayman M. Schenk P. Stephan K. Turrini D. Yingst R. A. Dawn Science Team Geoscientific Mapping of Vesta by the Dawn Mission [#1213] The geologic objectives of the Dawn mission (orbiting Vesta in 2011/2012) are to derive Vesta’s shape, map the surface geology, understand the geological context, and contribute to the determination of the asteroids’ origin and evolution.
    [Show full text]
  • Axial and Orbital Precession
    CS_Ch11_Astronomy 2/28/05 4:01 PM Page 689 Activity 3 Orbits and Effects The precession of Geo Words 41,000 year the Earth’s axis is cycle orbital plane: (also 25˚ axis now axis in one part of the 23.5˚ called the ecliptic or 22˚ range of 13,000 years plane of the ecliptic). precession cycle. axial tilt A plane formed by Another part is the path of the Earth the precession of around the Sun. the Earth’s orbit. orbital orbital inclination: the angle As the Earth plane plane between the orbital plane of the solar moves around the system and the actual Sun in its elliptical orbit of an object Obliquity Cycle Axial Precession orbit, the major around the Sun. axis of the Earth’s orbital ellipse is January July rotating about the conditions now Sun. In other Sun words, the orbit January July itself rotates conditions in about around the Sun! Earth 11,000 years These two Orbital Precession Combined Precession precessions (the Effects axial and orbital precessions) Figure 3 The tilt of the Earth’s axis and its orbital path about the combine to affect Sun go through several cycles of change. how far the Earth is from the Sun during the different seasons.This combined effect is called precession of the equinoxes, and this change goes through one complete cycle about every 22,000 years.Ten thousand years from now, about halfway through the precession cycle, winter will be from June to September, when the Earth will be farthest from the Sun during the Northern Hemisphere winter.That will make winters there even colder, on average.
    [Show full text]
  • Starry Starry Night Part 1
    Starry Starry Night Part 1 1. If a lunar eclipse occurs tonight, when is the soonest a solar eclipse can occur? A) Tomorrow B) In two weeks C) In six months D) In one year 2. The surface of the Sun is called its A) corona B) photosphere C) chromosphere D) atmosphere 3. Which moon in the Solar System has lakes and rivers on it: A) Triton B) Charon C) Titan D) Europa 4. The sixth planet from the Sun is: A) Mars B) Jupiter C) Saturn D) Uranus 5. The orbits of the planets and dwarf planets around the Sun are in the shape of: A) An eclipse B) A circle C) An ellipse D) None of the above 6. True or False: During the summer and winter solstices, nighttime and daytime are of equal length. 7 . The diameter of the observable universe is estimated to be A) 93 billion miles B) 93 billion astronomical units C) 93 billion light years D) 93 trillion miles 8. Asteroids in the same orbit as Jupiter -- in front and behind it -- are called: A) Greeks B) Centaurs C) Trojans D) Kuiper Belt Objects 9. Saturn's rings are made mostly of: A) Methane ice B) Water ice C) Ammonia ice D) Ice cream 10. The highest volcano in the Solar System is on: A) Earth B) Venus C) Mars D) Io 11. The area in the Solar System just beyond the orbit of Neptune populated by icy bodies is called A) The asteroid belt B) The Oort cloud C) The Kuiper Belt D) None of the above 12.
    [Show full text]
  • SOLAR OBLIQUITY INDUCED by PLANET NINE Elizabeth Bailey, Konstantin Batygin, Michael E
    Draft version July 21, 2016 Preprint typeset using LATEX style emulateapj v. 5/2/11 SOLAR OBLIQUITY INDUCED BY PLANET NINE Elizabeth Bailey, Konstantin Batygin, Michael E. Brown Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 Draft version July 21, 2016 ABSTRACT The six-degree obliquity of the sun suggests that either an asymmetry was present in the solar system's formation environment, or an external torque has misaligned the angular momentum vectors of the sun and the planets. However, the exact origin of this obliquity remains an open question. Batygin & Brown(2016) have recently shown that the physical alignment of distant Kuiper Belt orbits can be explained by a 5 20 m planet on a distant, eccentric, and inclined orbit, with an approximate perihelion distance− of 250⊕ AU. Using an analytic model for secular interactions between Planet Nine and the remaining giant∼ planets, here we show that a planet with similar parameters can naturally generate the observed obliquity as well as the specific pole position of the sun's spin axis, from a nearly aligned initial state. Thus, Planet Nine offers a testable explanation for the otherwise mysterious spin-orbit misalignment of the solar system. 1. INTRODUCTION In particular, interactions between the magnetosphere of The axis of rotation of the sun is offset by six degrees a young star and its protostellar disk can potentially lead from the invariable plane of the solar system (Souami to a wide range of stellar obliquities while leaving the & Souchay 2012). In contrast, planetary orbits have an coplanarity of the tilted disk intact (Lai et al.
    [Show full text]
  • Notes Unit IV-I “Mercury & Venus” S.W.B.A.T
    Notes Unit IV-I “Mercury & Venus” Name: ____________________ S.W.B.A.T • Identify _______________ characteristics of Mercury & Venus • Understand how the two _____________ planets compare • Discuss the evolutionary ______________ of both planets Planet Mercury • Smallest, closest & _______________ planet to orbit the Sun • Heavily cratered surface resembles the _______________ • Average _______________ from the Sun .39 AU or 58 million kilometers (36 million _______________) • 2440 km in _______________ or about .38 the size of Earth • _______________ the Sun in 88 days • Spins _______________ on its axis every 59 days (sidereal period) • Surface temperature ranges from - 300oF to + 800oF (over ___________ difference!) • Only inner planet besides _______________ to have a measurable magnetic field • Inner iron core (nucleus) is very _______________ • Iron core spins _______________ an electric/magnetic field effect like _______________ • Caloris Basin – very large _______________ structure near the equator created about ____ billion years ago • One of the _______________ impact basins in the Solar System • The impact created “_______________ terrain” on the other side of Mercury (ex.’s mountains, scarps & ____________ ) • Because of Mercury’s small size it _______________ quickly helping to form the “weird” crustal terrain • Very _______________ metallic/rock crust composition • _______________ axial tilt (3o) • Highly _______________ orbit (.206 compared to Earth’s .016) • No _______________ & no (real) atmosphere • Mercury may have
    [Show full text]