DOCSLIB.ORG

Atmospheres of the Terrestrial Planets. I

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Atmospheres of the Terrestrial Planets. I Terrestrial Planet Atmospheres Atmospheres in General • A layer of gas surrounding a solid/liquid body • The density decreases with height – hydrostac equilibrium • Temperature depends on energy input • May include condensates (clouds) • May have precipitaon Atmospheres are Insignificant • Earth’s atmosphere % by mass: 0.00009 Atmospheres are Insignificant • Earth’s atmosphere % by mass: 0.00009 NOT! Terrestrial Atmosphere Stats Physics of Atmospheres • Pressure balance (hydrostac equilibrium) • Gas pressure ~ nT – N: gas density – T: gas temperature • Pressure is the result of collisions between atoms/molecules • Thermal energy kT = kine<c energy ½ mv2 Atmospheric Pressure Earth standard atmosphere: • 1 bar = 106 dynes/cm2 = 105 N/m2 = 105 Pa • 1 bar = 750 tor (mm of Hg) = 29.5 in • 1 bar = 14.7lbs/sq in • 1 atmosphere = 1.03 bar • Density ~ 1019 molecules/cm3 Atmospheric Pressure Top of the Atmosphere • No clear upper boundary – ρ and P decrease with al<tude. – On Earth, above ~ 60 km, “edge of space” – Low density gas extends for several hundred km more. • Satellites in low Earth orbits experience fricon Exosphere Thermosphere Mesosphere Stratosphere Troposphere Levels of the Atmosphere • Troposphere: • temperature falls with height • Heated from below: Unstable to convecon • Stratosphere: • temperature rises with height • Heated in-situ by solar UV • Exosphere: • essen<ally the vacuum of space • Heated by X-rays • Includes the ionosphere Troposphere • Sunlight heats Earth's surface • Earth re-radiates in IR • Troposphere greenhouse gases absorb IR – T decreases with height. – The adiabat – Convec<on and weather The Adiabat On an adiabat heat is not transferred • Rising air: pressure decreases, volume increases, temperature falls (orographic uplih) • Falling air: pressure increases, volume decreases, temperature increases (chinook winds) • If temperature increases faster than surroundings, air becimes buoyant (convec<ve instability) • If temperature falls faster than surroundings, air falls (convec<vely stable) This drives weather Stratosphere • O3 absorbs UV photons • Top of stratosphere absorbs more UV than boom • T increases with al<tude • No convecon • stagnant • Every terrestrial planet? Thermosphere • All gases absorb X-rays • Solar X-rays → absorbed by top of thermosphere – T increases with al<tude • Gas: (mostly) ions + free electrons – Ionosphere reflects radio broadcasts Exosphere • High T, low density gas – Collisions rare • Some ar<ficial satellites orbit in Earth's exosphere • Atmospheric gases escape from Earth's exosphere Comparison of Terrestrial Planets Atmospheric Scale Height • Ρ(h) = P(0) e-h/h0 • h0=kT/mg – k = Boltzmann constant – T=temperature – m=mass of par<cle – g=gravitaonal acceleraon • Density falls off exponen<ally with height • Mathemacally, atmosphere never ends Atmospheric Scale Height • Ρ(h) = P(0) e-h/h0 For Earth: T = 14C (287K) • h0=kT/mg <m> = 28.9 AMU = 5 x 10-23 gm – k = Boltzmann constant g = 980 cm/s2 – T=temperature h = 8.1 km = 5 miles – m=mass of par<cle – g=gravitaonal acceleraon Examples (constant T): • Density falls off exponen<ally Denver (1 mile): P=0.8 atm with height Mauna Kea: P=0.6 atm Mt Everest: P=0.33 atm • h is the distance the pressure drop by a factor of e (2.718) 37000 h: P=0.25 atm 100 km: P=4 x 10-6 atm The Magnetosphere The Aurora Van Allen Belts • Charged par<cles (protons and electrons) trapped in Earth’s magnetosphere – Inner belt: 1600 – 13000 km – Outer belt: 19,000 – 40,000 km Atmospheric Escape • Thermal energy kT = kine<c energy ½ mv2 • vT = √(2kT/m) • Escape velocity vesc= √(2GmMp/r) The Greenhouse. I. • A bare rock radiates ~ like a blackbody. • The atmosphere modifies the equilibrium – Clouds increase the reflec<vity (albedo) – Greenhouse gases absorb IR re-radiaon from the planet – Inefficient radiaon èhigher than expected T • Atmospheres warm planetary surfaces Energy Balance 2 2 (1-a) πR⊕ (L¤ / 4π d ) ⇒ ⇓ 2 4 4πR⊕ σT⊕ The Greenhouse. II. • Earth mean temperature: 287 K • Earth equilibrium temperature (a=0): 280 K • Earth equilibrium temperature (a=0.39): 247 K • Greenhouse effect: 40K Why is the Sky Blue? • Molecules and dust scaer photons. • Scaering is most efficient when the wavelength is close to the size of the scaerer – Rayleigh scaering ~ λ-4 – Blue light is scaered more efficiently than red light – The blue sky is scaered blue photons – Most Rayleigh scaering by N2 molecules – Cigareie smoke appears bluish • The sun appears yellow because blue has been scaered out • Why is the Sun red at sunrise/sunset? The sky is blue Polarizaon Rayleigh scaered light is polarized Dusk Why is the Eclipsed Moon Red? Why is the Mar<an Sky Red? Mar<an Sunset Weather and Climate Weather: local variaons due to wind, storms, pressure changes, etc. • Driven by convecon Climate: long term behavior • Driven by – Insolaon – atmospheric changes • Composion • circulaon Weather and Climate • Energy input is Solar • Atmospheric mo<ons are driven by local heang (convec<on) • Hot air rises (lower density); cold air falls • Precipitaon cools atmosphere Basic Atmospheric Circulaon – no rotaon (Hadley cells) What Winds do for a Planet • Equator heated more than poles • Hadley cell transport heat poleward – Earth's poles warmer than otherwise would be Coriolis Forces Coriolis Forces: A result of mo<on in a moving reference frame Terrestrial Winds What drives the wind? Coriolis effect breaks each circulaon cell into 3 • Explains global wind paerns (consider surface air movement) Coriolis effect: convec<on cells → East-West winds. • Venus: rotaon too slow (day is longer than year) • Mars: too small • Jovian planets: Coriolis effect important. Storms Condensaon in the Atmosphere: Clouds • Allow precipitaon (rain, snow, hail, ...) • Alter energy balance – Sunlight reflected—cools planet (increases albedo) – Made of greenhouse gases—warms planet • Water vapor carried to high al<tude condenses – Large droplets fall → precipitaon • Linked to convec<on – Strong convec<on → more clouds and precipitaon – Equatorial regions: high rainfall due to more sunlight – Moisture removed by the <me convec<on reaches deserts Next: Atmospheres of the other terrestrial planets .
Load more

Recommended publications
  • Geological Timeline
    Geological Timeline In this pack you will find information and activities to help your class grasp the concept of geological time, just how old our planet is, and just how young we, as a species, are. Planet Earth is 4,600 million years old. We all know this is very old indeed, but big numbers like this are always difficult to get your head around. The activities in this pack will help your class to make visual representations of the age of the Earth to help them get to grips with the timescales involved. Important EvEnts In thE Earth’s hIstory 4600 mya (million years ago) – Planet Earth formed. Dust left over from the birth of the sun clumped together to form planet Earth. The other planets in our solar system were also formed in this way at about the same time. 4500 mya – Earth’s core and crust formed. Dense metals sank to the centre of the Earth and formed the core, while the outside layer cooled and solidified to form the Earth’s crust. 4400 mya – The Earth’s first oceans formed. Water vapour was released into the Earth’s atmosphere by volcanism. It then cooled, fell back down as rain, and formed the Earth’s first oceans. Some water may also have been brought to Earth by comets and asteroids. 3850 mya – The first life appeared on Earth. It was very simple single-celled organisms. Exactly how life first arose is a mystery. 1500 mya – Oxygen began to accumulate in the Earth’s atmosphere. Oxygen is made by cyanobacteria (blue-green algae) as a product of photosynthesis.
    [Show full text]
  • Mars Mars Is the Fourth Terrestrial Planet. It Is Smaller in Size Than
    Mars Mars is the fourth terrestrial planet. It is smaller in size than Earth and Venus, but larger than Mercury. Of the planets, Mars is the most hospitable to visiting humans, as it has an atmosphere, though it has no oxygen and is very thin. In the early days of the solar system, Mars has had liquid water on its surface, which is proved by the existence of various minerals that require liquid water to form. The current atmosphere of Mars is too thin and cold for liquid water to exist for long periods of times. Still, there is evidence of terrain shaped by flowing liquids, which are probably temporary flows or floods caused by the melting of ice in the ground. Mars has seasons like the Earth, and ice caps at the poles that grow and shrink over the course of the year. They consist of water ice and CO2 ice, the latter varying more with the seasons. One year on Mars is a bit less than two Earth years. Mars has two moons, Phobos and Deimos. They are very small compared to Mars, and are likely to be asteroids captured by Mars's gravity in the distant past. Giant planets and their moons The outer four planets of the solar system are known as the giant planets, because of their large size (compared to the terrestrial planets). The giant planets of our solar system can be further divided into two categories: gas giants (Jupiter and Saturn) and ice giants (Uranus and Neptune). The gas giants consist mainly of hydrogen (up to 90%) and helium, while the ice giants are mostly "ices" such as water and ammonia, with only some 20% of hydrogen.
    [Show full text]
  • Outer Planets: the Ice Giants
    Outer Planets: The Ice Giants A. P. Ingersoll, H. B. Hammel, T. R. Spilker, R. E. Young Exploring Uranus and Neptune satisfies NASA’s objectives, “investigation of the Earth, Moon, Mars and beyond with emphasis on understanding the history of the solar system” and “conduct robotic exploration across the solar system for scientific purposes.” The giant planet story is the story of the solar system (*). Earth and the other small objects are leftovers from the feast of giant planet formation. As they formed, the giant planets may have migrated inward or outward, ejecting some objects from the solar system and swallowing others. The giant planets most likely delivered water and other volatiles, in the form of icy planetesimals, to the inner solar system from the region around Neptune. The “gas giants” Jupiter and Saturn are mostly hydrogen and helium. These planets must have swallowed a portion of the solar nebula intact. The “ice giants” Uranus and Neptune are made primarily of heavier stuff, probably the next most abundant elements in the Sun – oxygen, carbon, nitrogen, and sulfur. For each giant planet the core is the “seed” around which it accreted nebular gas. The ice giants may be more seed than gas. Giant planets are laboratories in which to test our theories about geophysics, plasma physics, meteorology, and even oceanography in a larger context. Their bottomless atmospheres, with 1000 mph winds and 100 year-old storms, teach us about weather on Earth. The giant planets’ enormous magnetic fields and intense radiation belts test our theories of terrestrial and solar electromagnetic phenomena.
    [Show full text]
  • The Solar System Cause Impact Craters
    ASTRONOMY 161 Introduction to Solar System Astronomy Class 12 Solar System Survey Monday, February 5 Key Concepts (1) The terrestrial planets are made primarily of rock and metal. (2) The Jovian planets are made primarily of hydrogen and helium. (3) Moons (a.k.a. satellites) orbit the planets; some moons are large. (4) Asteroids, meteoroids, comets, and Kuiper Belt objects orbit the Sun. (5) Collision between objects in the Solar System cause impact craters. Family portrait of the Solar System: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, (Eris, Ceres, Pluto): My Very Excellent Mother Just Served Us Nine (Extra Cheese Pizzas). The Solar System: List of Ingredients Ingredient Percent of total mass Sun 99.8% Jupiter 0.1% other planets 0.05% everything else 0.05% The Sun dominates the Solar System Jupiter dominates the planets Object Mass Object Mass 1) Sun 330,000 2) Jupiter 320 10) Ganymede 0.025 3) Saturn 95 11) Titan 0.023 4) Neptune 17 12) Callisto 0.018 5) Uranus 15 13) Io 0.015 6) Earth 1.0 14) Moon 0.012 7) Venus 0.82 15) Europa 0.008 8) Mars 0.11 16) Triton 0.004 9) Mercury 0.055 17) Pluto 0.002 A few words about the Sun. The Sun is a large sphere of gas (mostly H, He – hydrogen and helium). The Sun shines because it is hot (T = 5,800 K). The Sun remains hot because it is powered by fusion of hydrogen to helium (H-bomb). (1) The terrestrial planets are made primarily of rock and metal.
    [Show full text]
  • Comparative Habitability of Transiting Exoplanets
    Draft version October 1, 2015 A Preprint typeset using LTEX style emulateapj v. 04/17/13 COMPARATIVE HABITABILITY OF TRANSITING EXOPLANETS Rory Barnes1,2,3, Victoria S. Meadows1,2, Nicole Evans1,2 Draft version October 1, 2015 ABSTRACT Exoplanet habitability is traditionally assessed by comparing a planet’s semi-major axis to the location of its host star’s “habitable zone,” the shell around a star for which Earth-like planets can possess liquid surface water. The Kepler space telescope has discovered numerous planet candidates near the habitable zone, and many more are expected from missions such as K2, TESS and PLATO. These candidates often require significant follow-up observations for validation, so prioritizing planets for habitability from transit data has become an important aspect of the search for life in the universe. We propose a method to compare transiting planets for their potential to support life based on transit data, stellar properties and previously reported limits on planetary emitted flux. For a planet in radiative equilibrium, the emitted flux increases with eccentricity, but decreases with albedo. As these parameters are often unconstrained, there is an “eccentricity-albedo degeneracy” for the habitability of transiting exoplanets. Our method mitigates this degeneracy, includes a penalty for large-radius planets, uses terrestrial mass-radius relationships, and, when available, constraints on eccentricity to compute a number we call the “habitability index for transiting exoplanets” that represents the relative probability that an exoplanet could support liquid surface water. We calculate it for Kepler Objects of Interest and find that planets that receive between 60–90% of the Earth’s incident radiation, assuming circular orbits, are most likely to be habitable.
    [Show full text]
  • Discovery of a Low-Mass Companion to a Metal-Rich F Star with the Marvels Pilot Project
    The Astrophysical Journal, 718:1186–1199, 2010 August 1 doi:10.1088/0004-637X/718/2/1186 C 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A. DISCOVERY OF A LOW-MASS COMPANION TO A METAL-RICH F STAR WITH THE MARVELS PILOT PROJECT Scott W. Fleming1,JianGe1, Suvrath Mahadevan1,2,3, Brian Lee1, Jason D. Eastman4, Robert J. Siverd4, B. Scott Gaudi4, Andrzej Niedzielski5, Thirupathi Sivarani6, Keivan G. Stassun7,8, Alex Wolszczan2,3, Rory Barnes9, Bruce Gary7, Duy Cuong Nguyen1, Robert C. Morehead1, Xiaoke Wan1, Bo Zhao1, Jian Liu1, Pengcheng Guo1, Stephen R. Kane1,10, Julian C. van Eyken1,10, Nathan M. De Lee1, Justin R. Crepp1,11, Alaina C. Shelden1,12, Chris Laws9, John P. Wisniewski9, Donald P. Schneider2,3, Joshua Pepper7, Stephanie A. Snedden12, Kaike Pan12, Dmitry Bizyaev12, Howard Brewington12, Olena Malanushenko12, Viktor Malanushenko12, Daniel Oravetz12, Audrey Simmons12, and Shannon Watters12,13 1 Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 326711-2055, USA; scfl[email protected]fl.edu 2 Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USA 3 Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA 16802, USA 4 Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA 5 Torun´ Center for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, 87-100, Torun,´ Poland 6 Indian Institute of Astrophysics, Bangalore 560034, India 7 Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA 8 Department of Physics, Fisk University, 1000 17th Ave.
    [Show full text]
  • Dynamical Evolution and Bombardment of the Early Solar System: a Few Highlights from the Last 50 Years
    50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132) 1545.pdf DYNAMICAL EVOLUTION AND BOMBARDMENT OF THE EARLY SOLAR SYSTEM: A FEW HIGHLIGHTS FROM THE LAST 50 YEARS. W. F. Bottke1 1Southwest Research Institute and NASA’s SSERVI-ISET Team, Boulder, CO ([email protected]). Introduction. Over the last several decades, there orbital migration of Jupiter and Saturn in a gas disk, has been a transformation in our theoretical under- Jupiter could have migrated inward all the way to ~1.5 standing of early Solar System evolution. Historically, AU from the Sun. At that point Jupiter and Saturn it was thought that the planets and small bodies formed could have become trapped in their mutual 2:3 reso- near their current locations. Starting in the 1980’s with nance and would have begun to move outward. pioneering work by Ward, Lin, and Papaloizou, (for The Grand Tack model studied the gravitational planet–gas disk interactions) in the late 1970s and Fer- scattering of asteroids by Jupiter and Saturn during nandez and Ip (for planet–planetesimal disk interac- their inward, then outward migration. This model not tions) in the early 1980s, however, it has now become only reproduces the mass and mixture of spectral types clear that the structure of the Solar System most likely in the asteroid belt, but also truncates the planetesimal changed as the planets grew and migrated [e.g., 1, 2]. disk from which the terrestrial planets form, as in Han- Evidence for giant planet migration can be found in sen’s work. This allowed them to form a low-mass the orbital structures of the Kuiper belt, Trojans, irreg- Mars.
    [Show full text]
  • Terrestrial Planets in High-Mass Disks Without Gas Giants
    A&A 557, A42 (2013) Astronomy DOI: 10.1051/0004-6361/201321304 & c ESO 2013 Astrophysics Terrestrial planets in high-mass disks without gas giants G. C. de Elía, O. M. Guilera, and A. Brunini Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata and Instituto de Astrofísica de La Plata, CCT La Plata-CONICET-UNLP, Paseo del Bosque S/N, 1900 La Plata, Argentina e-mail: [email protected] Received 15 February 2013 / Accepted 24 May 2013 ABSTRACT Context. Observational and theoretical studies suggest that planetary systems consisting only of rocky planets are probably the most common in the Universe. Aims. We study the potential habitability of planets formed in high-mass disks without gas giants around solar-type stars. These systems are interesting because they are likely to harbor super-Earths or Neptune-mass planets on wide orbits, which one should be able to detect with the microlensing technique. Methods. First, a semi-analytical model was used to define the mass of the protoplanetary disks that produce Earth-like planets, super- Earths, or mini-Neptunes, but not gas giants. Using mean values for the parameters that describe a disk and its evolution, we infer that disks with masses lower than 0.15 M are unable to form gas giants. Then, that semi-analytical model was used to describe the evolution of embryos and planetesimals during the gaseous phase for a given disk. Thus, initial conditions were obtained to perform N-body simulations of planetary accretion. We studied disks of 0.1, 0.125, and 0.15 M.
    [Show full text]
  • Symposium on Telescope Science
    Proceedings for the 26th Annual Conference of the Society for Astronomical Sciences Symposium on Telescope Science Editors: Brian D. Warner Jerry Foote David A. Kenyon Dale Mais May 22-24, 2007 Northwoods Resort, Big Bear Lake, CA Reprints of Papers Distribution of reprints of papers by any author of a given paper, either before or after the publication of the proceedings is allowed under the following guidelines. 1. The copyright remains with the author(s). 2. Under no circumstances may anyone other than the author(s) of a paper distribute a reprint without the express written permission of all author(s) of the paper. 3. Limited excerpts may be used in a review of the reprint as long as the inclusion of the excerpts is NOT used to make or imply an endorsement by the Society for Astronomical Sciences of any product or service. Notice The preceding “Reprint of Papers” supersedes the one that appeared in the original print version Disclaimer The acceptance of a paper for the SAS proceedings can not be used to imply or infer an endorsement by the Society for Astronomical Sciences of any product, service, or method mentioned in the paper. Published by the Society for Astronomical Sciences, Inc. First printed: May 2007 ISBN: 0-9714693-6-9 Table of Contents Table of Contents PREFACE 7 CONFERENCE SPONSORS 9 Submitted Papers THE OLIN EGGEN PROJECT ARNE HENDEN 13 AMATEUR AND PROFESSIONAL ASTRONOMER COLLABORATION EXOPLANET RESEARCH PROGRAMS AND TECHNIQUES RON BISSINGER 17 EXOPLANET OBSERVING TIPS BRUCE L. GARY 23 STUDY OF CEPHEID VARIABLES AS A JOINT SPECTROSCOPY PROJECT THOMAS C.
    [Show full text]
  • Explore Jupiter's Family Secrets: JUMP to JUPITER
    ~ LPI EDUCATION/PUBLIC ENGAGEMENT SCIENCE ACTIVITIES ~ Explore Jupiter’s Family Secrets: JUMP TO JUPITER OVERVIEW — Participants jump through a course from the grapefruit-sized “Sun,” past poppy-seed-sized “Earth,” and on to marble-sized “Jupiter” — and beyond! By counting the jumps needed to reach each object, children experience first-hand the vast scale of our solar system. WHAT’S THE POINT? The solar system is a family of eight planets, an asteroid belt, several dwarf planets, and numerous small bodies such as comets in orbit around the Sun. The four inner terrestrial planets are small compared to the four outer gas giants. The distance between planetary orbits is large compared to their sizes. Models can be used to answer questions about the solar system. MATERIALS — Facility needs: ☐ A large area, such as a long hallway, a sidewalk that extends for several blocks, or a football field (see Preparation section for setup options) ☐ A variety of memorable objects used to represent the Sun and planets, such as (use Jump to Jupiter: Planet Sizes and Distances to identify an appropriately-sized substitutes as needed): ☐ 1 (4 inch) grapefruit ☐ 2 (½ inch) marbles ☐ 2 peppercorns ☐ 2 poppy seeds ☐ 3 pepper flakes ☐ 1 pinch of fine sand or dust ☐ 1 set of solar system object markers created (preferably in color) from: • 1 set of Jump to Jupiter: Planet Information Sheets OR Credit: Enid Costley, Library of Virginia • Posters created by the participants OR • Optional: 1 set of Our Solar System lithographs (NASA educational product number LS-2013-07-003-HQ):
    [Show full text]
  • Formation of Telluric Planets and the Origin of Terrestrial Water
    BIO Web of Conferences 2, 01003 (2014) DOI: 10.1051/bioconf/20140201003 C Owned by the authors, published by EDP Sciences, 2014 Formation of telluric planets and the origin of terrestrial water Sean Raymond1;a 1Laboratoire d’Astrophysique de Bordeaux, UMR 5804 Abstract. Simulations of planet formation have failed to reproduce Mars’ small mass (compared with Earth) for 20 years. Here I will present a solution to the Mars problem that invokes large-scale migration of Jupiter and Saturn while they were still embedded in the gaseous protoplanetary disk. Jupiter first migrated inward, then "tacked" and migrated back outward when Saturn caught up to it and became trapped in resonance. If this tack occurred when Jupiter was at 1.5 AU then the inner disk of rocky planetesimals and em- bryos is truncated and the masses and orbits of all four terrestrial planet are quantitatively reproduced. As the giant planets migrate back outward they re-populate the asteroid belt from two different source populations, matching the structure of the current belt. C-type material is also scattered inward to the terrestrial planet-forming zone, delivering about the right amount of water to Earth on 10-50 Myr timescales. 1 Introduction 2 The formation of terrestrial planets As described in the Introduction, the final stages of terrestrial planet formation take place in the presence of any giant planets that may have formed. In addition, it is during this phase that bodies are large enough that during gravitational close encounters they can obtain large eccentricities. Thus, the feeding zones of the terrestrial planets are determined during their final accretion.
    [Show full text]
  • Arxiv:2106.07648V1 [Astro-Ph.EP] 14 Jun 2021 Behaviors from Periodic, E.G., Kepler-1520 B (Rappaport Et Al
    Draft version June 16, 2021 Typeset using LATEX default style in AASTeX62 LBT Reveals Large Dust Particles and a High Mass Loss Rate for K2-22 b Everett Schlawin,1 Kate Y. L. Su,1 Terry Herter,2 Andrew Ridden-Harper,2, 3 and Daniel´ Apai1, 4 1Steward Observatory The University of Arizona 933 North Cherry Avenue Tucson, AZ 85721, USA 2Astronomy Department Cornell University Ithaca NY 14853 3Carl Sagan Institute Cornell University Ithaca NY 14853 4Lunar and Planetary Laboratory The University of Arizona 1629 E. University Blvd. Tucson, AZ 85721, USA ABSTRACT The disintegrating planet candidate K2-22 b shows periodic and stochastic transits best explained by an escaping debris cloud. However, the mechanism that creates the debris cloud is unknown. The grain size of the debris as well as its sublimation rate can be helpful in understanding the environment that disintegrates the planet. Here, we present simultaneous photometry with the g band at 0.48 µm and KS band at 2.1 µm using the Large Binocular Telescope. During an event with very low dust activity, we put a new upper limit on the size of the planet of 0.71 R⊕ or 4500 km. We also detected a medium-depth transit which can be used to constrain the dust particle sizes. We find that the median particle size must be larger than about 0.5 to 1.0 µm, depending on the composition of the debris. This leads to a high mass loss rate of about 3 × 108 kg/s that is consistent with hydrodynamic escape models.
    [Show full text]