DOCSLIB.ORG

Nebula Theory

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Planet Formation From Dust to Planetesimals Coagulation of dust grains forms millimeter- and centimeter-sized objects e m i t g n i p p o t S (Dominik and Tielens, 1997) Physical Characteristics MAGIC Drag forces Collisional coalescence of cm-sized particles Strong -> Week results in the formation of larger objects and Chemical binding Strong -> Week eventually planetesimals (km-sized). Surface gravity Week -> Strong Formation of Terrestrial Planets Planetary embryos are formed in ~10,000 y, separated by a few Runaway Growth mutual Hill radii. Gravitational interaction causes collisions among Accretion of embryos is a planetesimals and results in local process. the formation of Mercury- to Mars-sized objects (planetary embryo) Ida and Makino (1993) Kokubo and Ida (1995, 1996, 1998) 1 Final Stage What if the embryos existed also in the asteroid belt? Giant impacts among high velocity embryos that result in terrestrial planets in ~100 million years. What if the embryos existed also in the asteroid belt? Water & Earth - Current location of Earth too close to the Sun to retain water -The icy bodies appear at distances of 4.0 AU and larger -Earth must have acquired its water from larger distances The variation of relative water content with distance from the Sun implies that ASTEROIDS (2.5-4.2 AU) OR COMETS (> 30 AU)? water should have been accreted from distant material. D/H (x 10-6) Halley 260-350 Courtesy of F. Robert Hyakutake 280-300 Hale Bopp 250-410 The D/H ratio of Earth’s water rules out a dominant contribution of comets and suggests an asteroidal origin Numerical integrations also show that comets could have contributed at most 10% of the current water on Earth 2 WATER FROM ASTEROIDS Water Delivery According to asteroid • Earth is dry, ~0.05% H2O by mass. belt sculpting scenario, • Cometary late veneer: D/H too high? only 0.1% of the “primitive” asteroids • Giant wet asteroid(s) would have been • Disk snowstorms! (Kuchner, Youdin & Bate) accreted by the Earth. - Snowfall: 1”/day for 104 years Assuming 1 Earth mass of material and 10% water content this amounts to only 20% of the water currently on Images: Earth. Moreover it •Earth, arrived “early” in the • water world (Liss or Earth formation history Gibson • comets, ast belt Formation of Outer Planets - Gas-giants: Jupiter and Saturn i) Mostly gas (thick gaseous envelop) ii) Large rocky cores - Ice-giants: Uranus and Neptune JUPITER Need to form at a region where ice is available Outer planets must have formed at a region where gas and icy solid material stay abundant for the duration of their formation Disk Lifetime & Location of Snow Line Core-Accretion Model WATER FROM EMBRYOS (Gas-giant Planets) (Pollack et al. 1996) • Farther out in the protoplanetary disk where the temperature of the gas is lower, the density of solids is enhanced with rocky and icy planetesimals. • Such an enhancement of the solid density may cause collisional accumulation of solids and results in runaway growth to a mass of approximately10 Earth-masses in 0.5-1 million years. • These bodies may accrete gas (equivalent to 100 Earth-masses) from the disk within approximately 6-10 million years and form gas-giant planets. • The gas collapses and forms a thick envelope. Raymond et al., 2004 3 Stochasticity in the resulting water budget A large eccentric Jupiter inhibits the delivery of water to the inner S.S. Raymond et al., 2004 Chambers, 2001; Raymond et al., 2004 170 Etxrasolar Planets • explains the accretion of a LARGE amount of water -Close-in gaint planets (hot Jupiters) • The accreted water has the D/H ratio similar to that of carbonaceous chondritic origin -Eccentric orbits • The water accretion occurs DURING the formation of the Earth, NOT in a late veneer phase, in agreement with -Multi-planet systems geochemical modeling • The accretion of the water is a stochastic event, and therefore -Planets & binary stars explains why not all terrestrial planets had an identical primitive water budget (e.g.Mars) Planetary System Observations imply planets in binaries vs Binary Star System Circumbinary Disk Debris Disk GG Tau (a = 35 AU) HD 141569 Until a few years ago, it was Md = 0.2 Solar-mass separation ~950 AU generally believed that the collapse of a molecular cloud would result in the formation of a planetary system around a single star, or the formation of a dual-star system with no planets. Krist et al. 2005 Clampin et al. 2003 4 • Approximately 20% of extrasolar planets are in binary or multi-star systems • Almost all these binaries are wide (250-6500 AU) • γ Cephei (~ 18.5 AU), GJ 86 (~20 AU), and HD188753 (~12 AU) are binary or multi-star systems with at least one Jupiter-like planet Binary and multi-star systems with planets (Haghighipour, 2005) 6H6H6H6H HD142 (GJ 9002) HD3651HD9826 (Upsilon$K HD13445 (GJ 86) HD19994HD22049 (Epsilon(P HD27442 HD40979 HD41004 HD75732 (55 Cnc) HD80606 HD89744 HD114762 HD 117176 (70 Vir)HD120136 (Tau% HD121504 HD137759HD143761 (Rho&I HD178911 HD186472 (16 Cyg) HD190360 (GJ 777 A) HD192263 HD195019 HD213240 HD217107 HD219449 HD219542 HD222404 (Gamma&LOLP HD178911 PSR B1257-20 PSR B1620-26 γ Cephei 0.37-0.75 solar-mass 1.59 solar-mass υ Andromedae 1.7 Jupiter-mass http://mcdonaldobservatory.org/news/releases/2002/1009.html Triple-star system HD 188753 Giant Planet Formation (Konacki, 2005) 0.96 M Current theories of planet formation can explain Sun formation of planets around single stars Primary Core Accretion 1.06 MSun 0.67 MSun Porb = 156 days a = 0.67 AU Planet=1.14 Jupiter-mass Period=3.35 days Porb = 25.7 years, a = 12.3 AU, e = 0.50 5 Stellar Companion Affects the Structure of the Nebula Stellar Companion Affects the Structure of the Nebula A stellar companion affects the disk by truncating it to -Equal Mass Binary System -Single Solar Mass Star -Stars = Solar Mass 0.5-0.1 times the semimajor axis of the binary -No stellar companion -Binary Semimajor Axis = 50 AU -20 AU radius -Binary Eccentricity = 0.5 Boss (2005) (Artymowicz and Lubow, 1994) Stellar Companion Affects the γ Cephei Dynamics of Planetesimals -Increasing eccentricity -Increasing mutual collisions 0.37-0.75 solar-mass -Increasing the possibility of 1.59 solar-mass coalescence/ejection Thiebault et al (2004) 1.7 Jupiter-mass http://mcdonaldobservatory.org/news/releases/2002/1009.html Planet=Black, Binary=Red Long-Term Stability Orbital Stability Orbital Parameters of γ Cephei Semimajor Axis = 18.5 ± 1.1 AU Semimajor Axis = 20.3 ± 0.7 AU Orbit of the Jupiter-size planet is Eccentricity = 0.361 ± 0.023 Eccentricity = 0.389 ± 0.170 Hatzes et al (2003) Griffin et al (2002) stable for all values of - binary eccentricity ≤ 0.45 Numerical Simulation - planet orbital inclination ≤ 60 deg Binary semimajor eccentricity: 0.2 to 0.65 in steps of 0.05 Planet orbital inclination: 0 to 80 deg Secondary mass: 0.3 to 0.92 solar-mass (Haghighipour, 2005) 6 Habitable Zone γ Cephei A Jupiter-like planet in a binary star system A habitable zone is a region where an Earth-like planet receives the same amount of radiation as Earth receives from Binary the Sun, and it develops similar habitable conditions as those Period = 20750.6579 ± 1568.6 days on the Earth. For a star with luminosity L(R,T), this implies Semimajor Axis = 18.5 ± 1.1 AU Eccentricity = 0.361 ± 0.023 4 2 −2 ⎛ T ⎞ ⎛ R ⎞ ⎛ r ⎞ F(r) = ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ FSun ()rEarth Primary Secondary ⎝ T ⎠ ⎝ R ⎠ ⎝ r ⎠ where Sun Sun Earth Mass = 1.59 Solar-masses Mass = 0.35-0.75 Solar-masses Radius = 4.66 Solar-radii Radius = 0.5 Solar-radii 1 −2 4 2 −2 F(r) = L(R,T) r = σ T R r = Star’s brightness Temp = 4900 K Temp = 3500 K 4π Distance = 45 light years T = Star’s surface temperature Age = 3 billion years Planet R = Star’s radius Period = 905.574 ± 3.08 days r = Radial distance of habitable region from central star Semimajor Axis = 2.13 ± 0.05 AU Eccentricity = 0.12 ± 0.05 Min Mass = 1.7 Jupiter-masses Surface Temperature of primary T = 4900 K Habitability Radius of primary R = 4.66 Solar-radii The habitable zone of the primary of γ Cephei is UNSTABLE Habitable zone of γ Cephei : 3.1 AU < r < 3.7 AU (Haghighipour, 2006) Habitable Zone 2.13 AU 18.5 AU 1 AU 1.67 Jupiter Mass Primary Secondary Region of Stability of a Terrestrial Planet Habitable Zone a = 20, 30, 40 AU 2.13 AU 16,17,18 AU e = 0.0, 0.2, 0.4 0.5 AU 1 AU 4 AU Stellar Companion 0.8 AU Jupiter 0.3 AU 7 Numerical Simulations Companion = 1 Solar-mass, Semimajor Axis = 20 AU, Eccentricity = 0 (Haghighipour & Raymond 2006) - Binary separation = 20, 30, 40 AU - Binary eccentricity = 0.0, 0.2, 0.4 - 120 Embryos randomly distributed from 0.5 to 4 AU - Mass of embryos = 0.01 to 0.1 Earth-mass - Total mass of the disk = 4 Earth-masses - Jupiter at 5 AU - Stochastic => 3 different run for each case 1 Companion = 1 Solar-mass, Semimajor Axis = 30 AU, Eccentricity = 0 (Haghighipour & Raymond 2006) 2 Companion = 1 Solar-mass, Semimajor Axis = 20 AU, Eccentricity = 0.2 (Haghighipour & Raymond 2006) 2 8 I) The key factor in the amount of water delivered is Jupiter's eccentricity II) Dynamics of Jupiter is affected by the eccentric orbit of the stellar companion III) It would be important to understand where giant planets will form in binary systems and to explore whether there is a systematic relation between the binary parameters and the orbit of the outermost giant planet? Studies of crater densities at sites of known ages (from Apollo Evidence for HB ~4.0-3.8 Gy ago samples) give flux data back to ~3.8 Gy ago, and show that the bombardment was ~100 times higher - The ages of the rocks collected on the Moon ~3.9-3.8 Gy -The ages of many basins (impact features > 200km) ~3.9-3.8 Gy (Wilhelms, 1987; Ryder, 1994) Cataclysmic LHB (Tera, Ryder, Kring, Cohen, Koeberl..) Suggests a sudden and short-lived cratering episode ~ 3.9 Gy ago, Slowly fading LHB (Tera et al.
Recommended publications
  • Using Kepler Systems to Constrain the Frequency and Severity of Dynamical Effects on Habitable Planets Alexander James Mustill Melvyn B

    Using Kepler Systems to Constrain the Frequency and Severity of Dynamical Effects on Habitable Planets Alexander James Mustill Melvyn B

    Using Kepler systems to constrain the frequency and severity of dynamical effects on habitable planets Alexander James Mustill Melvyn B. Davies Anders Johansen Dynamical instability bad for habitability • Excitation of eccentricity can shift HZ or cause extreme seasons (Spiegel+10, Dressing+10) • Planets may be scattered out of HZ • Planet-planet collisions may remove biospheres, atmospheres, water • Earth-like planets may be eaten by Neptunes/Jupiters Strong dynamical effects: scattering and Kozai • Scattering: closely-spaced giant planets excite each others’ eccentricities (Chatterjee+08) • Kozai: inclined external perturber (e.g. binary) can cause very large eccentricity fluctuations (Kozai 62, Lidov 62, Naoz 16) Relevance of inner systems to HZ • If you can • form a hot Jupiter through high-eccentricity migration • damage a Kepler system at few tenths of an au • you will damage the habitable zone too Relevance of inner systems intrinsically • Large number of single-candidate systems found by Kepler relative to multiples • Is this left over from formation? Or do the multiples evolve into singles through dynamics? (Johansen+12) • Informs models of planet formation • all the Kepler systems are interestingly different to the Solar system, but do we have two interestingly different channels of planet formation or only one? What do we know about the prevalence of strong dynamical effects? • So far know little about planets in HZ • What we do know: • Violent dynamical history strong contender for hot Jupiter migration • Many giants have high
  • Dynamics of the Terrestrial Planets from a Large Number of N-Body Simulations ∗ Rebecca A

    Dynamics of the Terrestrial Planets from a Large Number of N-Body Simulations ∗ Rebecca A

    Earth and Planetary Science Letters 392 (2014) 28–38 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Dynamics of the terrestrial planets from a large number of N-body simulations ∗ Rebecca A. Fischer , Fred J. Ciesla Department of the Geophysical Sciences, University of Chicago, 5734 S Ellis Ave, Chicago, IL 60637, USA article info abstract Article history: The agglomeration of planetary embryos and planetesimals was the final stage of terrestrial planet Received 6 September 2013 formation. This process is modeled using N-body accretion simulations, whose outcomes are tested by Received in revised form 26 January 2014 comparing to observed physical and chemical Solar System properties. The outcomes of these simulations Accepted 3 February 2014 are stochastic, leading to a wide range of results, which makes it difficult at times to identify the full Availableonline25February2014 range of possible outcomes for a given dynamic environment. We ran fifty high-resolution simulations Editor: T. Elliott each with Jupiter and Saturn on circular or eccentric orbits, whereas most previous studies ran an Keywords: order of magnitude fewer. This allows us to better quantify the probabilities of matching various accretion observables, including low probability events such as Mars formation, and to search for correlations N-body simulations between properties. We produce many good Earth analogues, which provide information about the mass terrestrial planets evolution and provenance of the building blocks of the Earth. Most observables are weakly correlated Mars or uncorrelated, implying that individual evolutionary stages may reflect how the system evolved even late veneer if models do not reproduce all of the Solar System’s properties at the end.
  • The Maunder Minimum and the Variable Sun-Earth Connection

    The Maunder Minimum and the Variable Sun-Earth Connection

    The Maunder Minimum and the Variable Sun-Earth Connection (Front illustration: the Sun without spots, July 27, 1954) By Willie Wei-Hock Soon and Steven H. Yaskell To Soon Gim-Chuan, Chua Chiew-See, Pham Than (Lien+Van’s mother) and Ulla and Anna In Memory of Miriam Fuchs (baba Gil’s mother)---W.H.S. In Memory of Andrew Hoff---S.H.Y. To interrupt His Yellow Plan The Sun does not allow Caprices of the Atmosphere – And even when the Snow Heaves Balls of Specks, like Vicious Boy Directly in His Eye – Does not so much as turn His Head Busy with Majesty – ‘Tis His to stimulate the Earth And magnetize the Sea - And bind Astronomy, in place, Yet Any passing by Would deem Ourselves – the busier As the Minutest Bee That rides – emits a Thunder – A Bomb – to justify Emily Dickinson (poem 224. c. 1862) Since people are by nature poorly equipped to register any but short-term changes, it is not surprising that we fail to notice slower changes in either climate or the sun. John A. Eddy, The New Solar Physics (1977-78) Foreword By E. N. Parker In this time of global warming we are impelled by both the anticipated dire consequences and by scientific curiosity to investigate the factors that drive the climate. Climate has fluctuated strongly and abruptly in the past, with ice ages and interglacial warming as the long term extremes. Historical research in the last decades has shown short term climatic transients to be a frequent occurrence, often imposing disastrous hardship on the afflicted human populations.
  • Curriculum Vitae

    Curriculum Vitae

    CURRICULUM VITAE Smadar Naoz September 2021 Contact University of California Los Angeles, Information Department of Physics & Astronomy 30 Portola Plaza, Box 951547 E-mail: [email protected] Los Angeles, CA 90095 WWW: http://www.astro.ucla.edu/∼snaoz/ Research Dynamics of planetary, stellar and black hole systems, which include formation of Hot Jupiters, Interests globular clusters, spiral structure, compact objects etc. Cosmology, structure formation in the early Universe, reionization and 21cm fluctuations. Education Tel Aviv University, Tel Aviv, Israel Ph.D. in Physics, January 2010 Hebrew University of Jerusalem, Jerusalem, Israel M.S. in Physics, Magna Cum Laude, 2004 B.S. in Physics 2002 Positions University of California, Los Angeles Associate professor since July 2019 Howard & Astrid Preston Term Chair in Astrophysics since July 2018 Assistant professor 2014-2019 Harvard Smithsonian CfA, Institute for Theory and Computation Einstein Fellow, September 2012 { June 2014 ITC Fellow, September 2011 { August 2012 Northwestern University, CIERA Gruber Fellow, September 2010 { August 2011 Postdoctoral associate in theoretical astrophysics, January 2010 { August 2010 Scholarships Helen B. Warner Prize, awarded by the American Astronomical Society, 2020 Honors and Scialog fellow, and accepted proposal, Signatures of Life in the Universe, 2020/2021 (conference Awards postponed to 2021 due to COVID-19) Career Commitment to Diversity, Equity and Inclusion Award, given by UCLA Academic Senate 2019. For other diversity awards, see xDEI. Hellman Fellows Award, awarded by Hellman Fellows Program, aimed to support the research of promising Assistant Professors who show capacity for great distinction in their research, June 2017 Multiple departmental teaching awards 2015-2019, see xTeaching, for details Sloan Research Fellowships awarded by the Alfred P.
  • Dynamical Models of Terrestrial Planet Formation

    Dynamical Models of Terrestrial Planet Formation

    Dynamical Models of Terrestrial Planet Formation Jonathan I. Lunine, LPL, The University of Arizona, Tucson AZ USA, 85721. [email protected] David P. O’Brien, Planetary Science Institute, Tucson AZ USA 85719 Sean N. Raymond, CASA, University of Colorado, Boulder CO USA 80302 Alessandro Morbidelli, Obs. de la Coteˆ d’Azur, Nice, F-06304 France Thomas Quinn, Department of Astronomy, University of Washington, Seattle USA 98195 Amara L. Graps, SWRI, Boulder CO USA 80302 Revision submitted to Advanced Science Letters May 23, 2009 Abstract We review the problem of the formation of terrestrial planets, with particular emphasis on the interaction of dynamical and geochemical models. The lifetime of gas around stars in the process of formation is limited to a few million years based on astronomical observations, while isotopic dating of meteorites and the Earth-Moon system suggest that perhaps 50-100 million years were required for the assembly of the Earth. Therefore, much of the growth of the terrestrial planets in our own system is presumed to have taken place under largely gas-free conditions, and the physics of terrestrial planet formation is dominated by gravitational interactions and collisions. The ear- liest phase of terrestrial-planet formation involve the growth of km-sized or larger planetesimals from dust grains, followed by the accumulations of these planetesimals into ∼100 lunar- to Mars- mass bodies that are initially gravitationally isolated from one-another in a swarm of smaller plan- etesimals, but eventually grow to the point of significantly perturbing one-another. The mutual perturbations between the embryos, combined with gravitational stirring by Jupiter, lead to orbital crossings and collisions that drive the growth to Earth-sized planets on a timescale of 107 − 108 years.
  • Three-Body Capture of Irregular Satellites: Application to Jupiter

    Three-Body Capture of Irregular Satellites: Application to Jupiter

    Icarus 208 (2010) 824–836 Contents lists available at ScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus Three-body capture of irregular satellites: Application to Jupiter Catherine M. Philpott a,*, Douglas P. Hamilton a, Craig B. Agnor b a Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA b Astronomy Unit, School of Mathematical Sciences, Queen Mary University of London, London E14NS, UK article info abstract Article history: We investigate a new theory of the origin of the irregular satellites of the giant planets: capture of one Received 19 October 2009 member of a 100-km binary asteroid after tidal disruption. The energy loss from disruption is sufficient Revised 24 March 2010 for capture, but it cannot deliver the bodies directly to the observed orbits of the irregular satellites. Accepted 26 March 2010 Instead, the long-lived capture orbits subsequently evolve inward due to interactions with a tenuous cir- Available online 7 April 2010 cumplanetary gas disk. We focus on the capture by Jupiter, which, due to its large mass, provides a stringent test of our model. Keywords: We investigate the possible fates of disrupted bodies, the differences between prograde and retrograde Irregular satellites captures, and the effects of Callisto on captured objects. We make an impulse approximation and discuss Jupiter, Satellites Planetary dynamics how it allows us to generalize capture results from equal-mass binaries to binaries with arbitrary mass Satellites, Dynamics ratios. Jupiter We find that at Jupiter, binaries offer an increase of a factor of 10 in the capture rate of 100-km objects as compared to single bodies, for objects separated by tens of radii that approach the planet on relatively low-energy trajectories.
  • Good Science, Bad Science: Teaching Evolution in the States. INSTITUTION Thomas B

    Good Science, Bad Science: Teaching Evolution in the States. INSTITUTION Thomas B

    DOCUMENT RESUME ED 447 099 SP 039 576 AUTHOR Lerner, Lawrence S. TITLE Good Science, Bad Science: Teaching Evolution in the States. INSTITUTION Thomas B. Fordham Foundation, Washington, DC. PUB DATE 2000-09-00 NOTE 66p. AVAILABLE FROM Thomas B. Fordham Foundation, 1627 K Street, N.W., Suite 600, Washington, DC 20006; Tel: 202-223-5452 or 888-TBF-7474 (toll-free); Fax: 202-223-9226; Web site: http://www.edexcellence.net. PUB TYPE Reports Descriptive (141) EDRS PRICE MF01/PC03 Plus Postage. DESCRIPTORS *Academic Standards; Biological Influences; Creationism; Elementary Secondary Education; *Evolution; Public Schools; *Science Education; *State Standards ABSTRACT This report discusses evolution in science education, evaluating the state-by-state treatment of evolution in science standards. It explains the role of evolution as an organizing principle for all the historical sciences. Seven sections include: "Introduction" (the key role of evolution in the sciences); "How Do Good Standards Treat Biological Evolution?" (controversial versus consensual knowledge and why students should learn about evolution); "Extrascientific Issues" (e.g., the diversity of anti-evolutionists, why anti-evolutionism persists, and how science standards reflect creationist pressures); "Evaluation of State Standards" (very good to excellent, good, satisfactory, unsatisfactory, useless or absent, and disgraceful); "Sample Standards"; "Further Analysis" (grades for science standards as a whole); and "Conclusions." Overall, 31 states do at least a satisfactory job of handling the central organizing principle of the historical sciences, 10 states do an excellent or very good job of presenting evolution, and 21 states do a good or satisfactory job. More than one-third of states do not do a satisfactory job.
  • A Summary and Analysis of Twenty-Seven Years of Geoscience Conceptions Research Kim A

    A Summary and Analysis of Twenty-Seven Years of Geoscience Conceptions Research Kim A

    Commentary: A Summary and Analysis of Twenty-Seven Years of Geoscience Conceptions Research Kim A. Cheek1 ABSTRACT Seventy-nine studies in geoscience conceptions appeared in peer-reviewed publications in English from 1982 through July 2009. Summaries of the 79 studies suggest certain recurring themes across subject areas: issues with terms, scale (temporal and spatial), role of prior experience, and incorrect application of everyday knowledge to geoscience phenomena. The majority of studies reviewed were descriptive and employed only one method of data collection and response type. Eleven-fourteen-year-olds and university undergraduates were most commonly represented in the samples. A small percentage of studies of geoscience conceptions of K-12 students made reference to standards documents or a curriculum as justification for the research design. More directed descriptive studies, along with greater parity between descriptive and intervention studies is needed. Greater attention to developmental theories of concept acquisition, national standards documents, and intersection with cognitive science literature are warranted. INTRODUCTION students to erroneous conclusions about geoscience Research into students’ conceptions in science has phenomena. Much of the research on student conceptions been going on for several decades. There is a large body of of geologic time and plate tectonics has been conducted scientific conceptions literature, though there is since her review. It is important to determine whether her comparatively less in the geosciences than in other earlier conclusions apply to newer research and novel scientific disciplines (Libarkin, S. Anderson, Science, topics. Dove did not discuss methodologies of the studies Beilfuss, & Boone, 2005; Dodick & Orion, 2003a). she reviewed. With the research base that has developed Nevertheless, a substantial body of research into students’ in the eleven years since her review, a discussion of geoscience conceptions has appeared within the past methodological trends is warranted.
  • AY2 - Overview of the Universe - Sample Questions for Midterm #1

    AY2 - Overview of the Universe - Sample Questions for Midterm #1

    AY2 - Overview of the Universe - Sample Questions for Midterm #1 MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Which of the following is smallest? 1) A) 1 AU B) size of a typical star C) 1 light-second D) size of a typical planet 2) On the scale of the cosmic calendar, in which the history of the universe is compressed to 1 year, 2) how long has human civilization (i.e., since ancient Egypt) existed? A) about a month B) a few hours C) less than a millionth of a second D) a few seconds E) about half the year 3) Patterns of stars in constellations hardly change in appearance over times of even a few 3) thousand years. Why? A) Stars are fixed and never move. B) Although most stars move through the sky, the brightest stars do not, and these are the ones that trace the patterns we see in the constellations. C) Stars within a constellation move together as a group, which tends to hide their actual motion and prevent the pattern from changing. D) Stars move, but they move very slowly—only a few kilometers in a thousand years. E) The stars in our sky actually move rapidly relative to us—thousands of kilometers per hour—but are so far away that it takes a long time for this motion to make a noticeable change in the patterns in the sky. 4) Which scientists played a major role in overturning the ancient idea of an Earth-centered 4) universe, and about when? A) Huygens and Newton; about 300 years ago B) Copernicus, Kepler, and Galileo; about 400 years ago C) Aristotle and Plato; about 2,000 years ago D) Aristotle and Copernicus; about 400 years ago E) Newton and Einstein; about 100 years ago TRUE/FALSE.
  • The Photoeccentric Effect and Proto-Hot Jupiters. I

    The Photoeccentric Effect and Proto-Hot Jupiters. I

    The Astrophysical Journal, 756:122 (13pp), 2012 September 10 doi:10.1088/0004-637X/756/2/122 C 2012. The American Astronomical Society. All rights reserved. Printed in the U.S.A. THE PHOTOECCENTRIC EFFECT AND PROTO-HOT JUPITERS. I. MEASURING PHOTOMETRIC ECCENTRICITIES OF INDIVIDUAL TRANSITING PLANETS Rebekah I. Dawson1 and John Asher Johnson2,3 1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-10, Cambridge, MA 02138, USA; [email protected] 2 Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125, USA 3 NASA Exoplanet Science Institute (NExScI), CIT Mail Code 100-22, 770 South Wilson Avenue, Pasadena, CA 91125, USA Received 2012 April 5; accepted 2012 July 9; published 2012 August 21 ABSTRACT Exoplanet orbital eccentricities offer valuable clues about the history of planetary systems. Eccentric, Jupiter-sized planets are particularly interesting: they may link the “cold” Jupiters beyond the ice line to close-in hot Jupiters, which are unlikely to have formed in situ. To date, eccentricities of individual transiting planets primarily come from radial-velocity measurements. Kepler has discovered hundreds of transiting Jupiters spanning a range of periods, but the faintness of the host stars precludes radial-velocity follow-up of most. Here, we demonstrate a Bayesian method of measuring an individual planet’s eccentricity solely from its transit light curve using prior knowledge of its host star’s density. We show that eccentric Jupiters are readily identified by their short ingress/ egress/total transit durations—part of the “photoeccentric” light curve signature of a planet’s eccentricity—even with long-cadence Kepler photometry and loosely constrained stellar parameters.
  • GACE Special Education Mathematics and Science Assessment (088) Curriculum Crosswalk Page 2 of 25 Required Coursework Numbers

    GACE Special Education Mathematics and Science Assessment (088) Curriculum Crosswalk Page 2 of 25 Required Coursework Numbers

    GACE® Special Education Mathematics and Science Assessment (088) Curriculum Crosswalk Required Coursework Numbers Subarea I. Mathematics (50%) Objective 1: Understands numbers and operations, including rational numbers, proportions, number theory, and estimation A. Understands operations and properties of rational numbers • Solves problems involving addition, subtraction, multiplication, and division of real numbers • Describes the effect an operation has on a given number; e.g., adding a negative, dividing by a fraction • Applies the order of operations • Uses place value to read and write numbers in standard and expanded form • Identifies or applies properties of operations on a number system; i.e., commutative, associative, distributive, identity • Compares, classifies, and orders real numbers • Performs operations involving exponents, including negative exponents • Simplifies and approximates radicals • Uses scientific notation to represent and compare numbers • Selects the appropriate operation to use for a given problem Copyright © 2018 by Educational Testing Service. All rights reserved. ETS and the ETS logo are registered trademarks of Educational Testing Service (ETS). Georgia Assessments for the Certification of Educators, GACE, and the GACE logo are registered trademarks of the Georgia Professional Standards Commission. Required Coursework Numbers B. Understands the relationships among fractions, decimals, and percents • Simplifies fractions to lowest terms • Finds equivalent fractions • Converts between fractions, decimals,
  • A Paucity of Proto-Hot Jupiters on Super-Eccentric Orbits

    A Paucity of Proto-Hot Jupiters on Super-Eccentric Orbits

    Submitted to ApJ on October 26th, 2012. Accepted on October 20th, 2014. Preprint typeset using LATEX style emulateapj v. 5/2/11 THE PHOTOECCENTRIC EFFECT AND PROTO-HOT JUPITERS III: A PAUCITY OF PROTO-HOT JUPITERS ON SUPER-ECCENTRIC ORBITS Rebekah I. Dawson1,2,3,7, Ruth A. Murray-Clay3,4, and John Asher Johnson3,5,6 Submitted to ApJ on October 26th, 2012. Accepted on October 20th, 2014. ABSTRACT Gas giant planets orbiting within 0.1 AU of their host stars, unlikely to have formed in situ, are evidence for planetary migration. It is debated whether the typical hot Jupiter smoothly migrated inward from its formation location through the proto-planetary disk or was perturbed by another body onto a highly eccentric orbit, which tidal dissipation subsequently shrank and circularized during close stellar passages. Socrates and collaborators predicted that the latter class of model should produce a population of super-eccentric proto-hot Jupiters readily observable by Kepler. We find a paucity of such planets in the Kepler sample, inconsistent with the theoretical prediction with 96.9% confidence. Observational effects are unlikely to explain this discrepancy. We find that the fraction of hot Jupiters with orbital period P > 3 days produced by the star-planet Kozai mechanism does not exceed (at two-sigma) 44%. Our results may indicate that disk migration is the dominant channel for producing hot Jupiters with P > 3 days. Alternatively, the typical hot Jupiter may have been perturbed to a high eccentricity by interactions with a planetary rather than stellar companion and began tidal circularization much interior to 1 AU after multiple scatterings.