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Halfway Around the World for 5 Minutes of data Learning about the atmosphere of Pluto Jeff Regester Greensboro Day School

Halfway Around the World for 5 Minutes of data

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Halfway Around the World for 5 Minutes of data . Learning about the atmosphere of Pluto. Jeff Regester Greensboro Day School. Outline. History of Pluto and Outer Solar System science Occultations New Horizons . Pluto’s Discovery. Discovered by accident, on purpose - PowerPoint PPT Presentation

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Halfway Around the World for 5 Minutes of data

Learning about the atmosphere of Pluto

Jeff RegesterGreensboro Day School

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Outline

• History of Pluto and Outer Solar System science

• Occultations• New Horizons

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Pluto’s Discovery

Discovered by accident, on purposeby Clyde Tombaugh, Lowell Observatory, 1930

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The Edgeworth-Kuiper Belt

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Leftovers

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Moons

Charon, discovered in 1978 by Jim Christie, USNO MPluto = MMercury/20

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Moons

Nix and Hydra, discovered in 2005 by Alan Stern et al, using HST

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Discovery of Atmosphere, 1988

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Occultationan eclipse of a star

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1992 Discovery of KBOs

Jewitt & Luu1992 QB1

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In 2004...

                                                                                              

A comparison of the size of Sedna, the largest known KBO in 2004, to various planets and moons. (NACO Team, 8.2-meter VLT (Yepun), ESO, apod040827)

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...and 2005

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Keck

HST

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Kepler’s Third Law

Dysnomia’s orbit P=16d MEris= 1.27 MPluto

Houston, we have a problem!

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We’ve been here before.

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2006, The IAU acts• RESOLUTION 5A

The IAU therefore resolves that "planets" and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:

(1) A "planet"1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2 , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects3 except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

1 The eight "planets" are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.2 An IAU process will be established to assign borderline objects into either dwarf planet and other categories.3 These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

goodbye “minor planets”

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RESOLUTION 6AThe IAU further resolves:

Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.

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Occultation Overview

Temperature PressureExtinction

Refractivity Bendingangle=>

Flux Position in shadow

=>=>

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Chris L. Peterson, Cloudbait Observatory, Colorado

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Lower Atmosphere Inversion(Ref: Elliot, Person and Qu 2003)

• Small Planet Case• No Ray Crossing• Geometric Optics• Clear Atmosphere

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12 June 2006 Occultation:Reconstructed Shadow Path

Predicting Occultations Ain’t Easy!

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At the mercy of the clouds.

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Occultations

12Jun2006

18Mar2007

31Jul2007

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Mt. Canopus Obs, Hobart, TAS

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Luxury!

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Conclusions from 2006 data• Pluto's bulk atmosphere (geometry):

– 1988 to 2006, pressure has increased by 0.98 ± 0.09 µbar, a factor of 2.17±0.21– For N2 surface vapor pressure equilibrium, this implies an increase in surface temperature

of 1.2-1.7 K.– Pressures consistant between 2002 and 2006

• Pluto’s upper atmosphere (model fit): – Non-isothermal. dT/dr = -0.127±0.028 K/km– Average (103.9±3.2 K) same as 2002 (104±2 K, isothermal fit),

and 1988 (104.0±7.3 K). – 99.4±3.1 K (ingress, 30.0 S, summer), 105.5±3.5 K (egress, 53.2 N, winter)

despite ~1500 less insolation averaged over the winter latitude, so not tied to insolation (in a straightforward way)

• Pluto’s lower atm, clear assumption (inversion):– As in 1988 & 2002, not isothermal. – Temperature inversion around 1210 - 1220 km.– Ingress & Egress are qualitatively similar, but the density perturbations differ in detail.

• Pluto’s lower atm, haze assumption (inversion, removing haze from model fit)– Top of haze poorly constrained.– Temperature perturbations qualitatively similar to those seen on Earth, Jupiter, Titan

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Observations - Mt. John(Blue channel; < ~627 nm)

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Observations - Mt. John(Red channel ; > ~627 nm)

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Mt. Canopus

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Observations - Portable Telescope (Tasmania)

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New Horizons on its way

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July 13th, 2015

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Questions?