Overview. Hubble Pluto Satellite Search Team reporting the discovery to the New Horizons Science Team on November 2, 2005 at the Kennedy Space Center

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1 The discovery of two new moons of Pluto Hubble Pluto Satellite Search Team reporting the discovery to the New Horizons Science Team on November 2, 2005 at the Kennedy Space Center Andrew Steffl Marc Buie (Lowell Observatory) Eliot Young Max Mutchler Space Telescope Science Institute Westminster Astronomical Society 8 February 2006 Hal Weaver (JHU/APL) S. Alan Stern Leslie Young John Spencer Bill Merline Max Mutchler (STScI) The first discovery of the New Horizons mission Overview Discovery of Pluto, Charon, and the Kuiper Belt Early Hubble observations of Pluto Hubble s Advanced Camera for Surveys Hubble mission support for New Horizons: discovery of two more Pluto satellites Confirming and following-up the discovery Implications, and related discoveries what is a planet? New Horizons mission to Pluto: launched 19 Jan 2006! More information via the web My hometown astronomy club Questions? Names for the new moons? The discovery of Pluto in 1930, and confirmation Clyde Tombaugh Discovery of the Kuiper Belt in 1992 The discovery of Pluto s moon Charon in 1978 James Christy & Robert Harrington U.S. Naval Observatory Washington, D.C.

2 Discovery of two new moons of Pluto Early Hubble observations of Pluto and Charon Press release image for new moons: the discovery was surprisingly easy for Hubble with ACS but not quite as easy as it looks here. Calibrating, pointing, and drizzling Hubble Servicing Mission 3B in March 2002: ACS installed Advanced Camera for Surveys (ACS) New satellite discovery observations Notice the star trails, cosmic rays, chip gap Hubble proposal designed by Weaver, Stern, et al., initially rejected, then accepted when STIS died Advanced Camera for Surveys (ACS) Wide Field Channel (WFC) covers entire orbital stability zone Pluto-Charon near chip gap: peek-a-boo! 4 long exposures on May 15 and May 18, 2005, using only 2 orbits Discovery on June 15: try it yourself 15 May 2005, frame 1

3 Notice the star trails, cosmic rays, chip gap Dithering across the chip gap now see anything? 15 May 2005, frame 2 15 May 2005, frame 3 Dithering across the chip gap now see anything? Looking for real objects among all the artifacts 15 May 2005, frame 4 15 May 2005, sum 4 frames Looking for real objects among all the artifacts Do it again 3 days later where are the moons? 15 May 2005, median 4 frames 18 May 2005, frame 1

4 Do it again 3 days later where are the moons? Dither across the gap where are the moons? 18 May 2005, frame 2 18 May 2005, frame 3 Do it again 3 days later where are the moons? Clean image 18 May 2005, frame 4 18 May 2005, median 4 frames Clean image New moons are roughly 3-4x farther out than Charon, with possible 6:4:1 orbital resonances S/2005 P 1 Charon S/2005 P 2 15 May 2005, median 4 frames 15 and 18 May 2005, median 8 frames

5 Pre-discovery observations in 2002 Hubble program by Buie & Young ACS High Resolution Channel Primarily designed to map surface features (albedo) of Pluto and Charon New moons marginally detected Further observations will definitively determine orbits, and hopefully confirm these detections: are the satellites where they should be? Initial thoughts Why is Pluto suddenly going so easy on us?!? Well-designed program: long exposure times (but not too long), two epochs the gap is OK Two objects! They somewhat validate each other, and assumptions about their similar orbits Surprised they are so close to Pluto and Charon: expecting any moons to be farther out, but they don t violate dynamical constraints (Stern, 1994) Could they be something other than moons? The checklist of possible explanations Detector artifacts? Optical ghosts or scattered light? Overlapping cosmic rays or star trails? Real, but asteroids? KBO (Plutinos)? New moons of Pluto! Confirmation and follow-up Independent discovery in Aug 2005 by Andrew Steffl Search other existing data: Hubble, Subaru Hubble follow-up: impossible until 15 Feb 2006 (2 gyros) Ground-based attempts to image the new moons in Sep/Oct: Keck, VLT, Gemini (difficult until spring 2006) Checklist of alternate explanations: rule them out? Confident enough to announce on 31 October 2005

6 Preliminary assumptions and implications Orbits are co-planar with Charon, nearly circular, possibly in stable resonances with each other No other moons of similar magnitude (unless artifacts hid them); very compact system Pluto first KBO with multiple satellites: implies there are probably many more Probably formed primordially with Charon (collision), not later (captured) Relative sizes of Pluto, Charon, and new moons (P1 and P2) 2300 km 1200 km P1 P2 ~100 km The new moons are roughly 12x smaller and 600x fainter than Charon, and 4000x fainter than Pluto What does a quadruple planet look like? Announcement and publications Animation produced with Celestia 9 Feb 2006 Weaver et al, 2005, IAU Circular 8625 Weaver et al., 2006, Nature (accepted) Stern et al., 2006, Nature (accepted) Steffl et al., Astronomical Journal (submitted) Pre-prints available online at: arxiv.org/archive/astro-ph Xena & Gabrielle Xena The 10 th planet? Pluto Moon Earth

7 Should we call Pluto a planet? I m neutral. But some things to consider Is Pluto just the first of many Kuiper Belt ice dwarf planets discovered? Is larger Xena the 10 th planet? Are slightly smaller Sedna, Quaoar planets? Ceres was called a planet for ~50 years, then re-classified as an asteroid (a precedent) Will we have only 8 planets, or hundreds of them? Is this a problem? Seems like progress to me. The IAU is working on it in the meanwhile, it is a harmless and healthy non-controversy Launch week, a.k.a Dad & Max Bill Nye David Levy New Horizons launch on 19 January 2006! Hal Weaver signing the Atlas V rocket Nerdstock Launch parties Jim Christy Annette and Patsy Tombaugh In memory of Clyde W. Tombaugh, the American astronomer who discovered Pluto in 1930, NASA's New Horizons spacecraft carries a small aluminum canister containing some of Tombaugh's cremated remains, donated by his family. These remains will fly past Pluto with New Horizons on July 14, 2015, and then on past Kuiper Belt objects in the succeeding years. The memorial canister, about two inches wide and half-an-inch tall, is attached to the inside, upper deck of the spacecraft. Its inscription reads: Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system's "third zone." Adelle and Muron's boy, Patricia's husband, Annette and Alden's father, astronomer, teacher, punster, and friend: Clyde W. Tombaugh ( )

8 Kuiper Belt Pluto 14 July 2015 Jupiter 28 Feb 2007 Launch 19 Jan 2006 Pluto-Charon Encounter Geometry Arrival July 14, 2015 P1 P2 Charon-Earth Occultation 14:17:50 Pluto-Earth Occultation 12:49:50 13:40 Charon Charon-Sun Occultation 14:15:41 12:40 Pluto Sun Earth 0.24 New Horizons mission S/C trajectory time ticks: 10 min Charon orbit time ticks: 12 hr Occultation: center time Position and lighting at Pluto C/A Distance relative to body center Pluto-Sun Occultation 12:49:00 Charon C/A 12:12:52 26,937 km km/s Pluto C/A 11:59:00 11,095 km km/s 11: Questions? RAS Junior Member, circa 1978 AND TWO LITTLE MOONS!

Is Pluto a planet? Historical overview. Personal anecdotes. Launch of the Hubble Space Telescope April 24, 1990

Is Pluto a planet? Historical overview. Personal anecdotes. Launch of the Hubble Space Telescope April 24, 1990 Is Pluto a planet? Max Mutchler Space Telescope Science Institute Johns Hopkins University Odyssey Lecture Series Hubble s Expanding Universe March 13, 2008 Historical overview Discovery of Pluto and it