Hubble Space Telescope Max Mutchler Space Telescope Science Institute Friends School Collection February 6, 2007

Overview Hubble mission background Discovery of Pluto (1930) and moon Charon (1978) Hubble observations of Pluto: discovery of moons Nix and Hydra (2005) Planet vote of 2006: planets and “dwarf planets” History: how many planets are there? The “problem” of being first: Ceres & Pluto Hubble observations of Ceres, another dwarf planet New Horizons and Dawn missions: follow the data, not the voting Inspiring students, and “teachable moments”

Hubble was launched into orbit by the Space Shuttle in 1990

Hubble is serviced in orbit by astronauts ?

Installed during Hubble Servicing Mission 3B March 2002 Advanced Camera for Surveys (ACS)

Space Telescope Science Institute (STScI) on the campus of Johns Hopkins University in Baltimore The “Home of Hubble”

Hubble observations of Ceres and Pluto What is a planet ? Eris and Dysnomia

The discovery of Pluto in 1930 Clyde Tombaugh

Blink-comparator that Tombaugh used to compare two images, and discover Pluto by it’s motion

The discovery of Pluto’s moon Charon in 1978 James Christy & Robert Harrington U.S. Naval Observatory Washington, D.C.

The discovery of two new moons of Pluto Weaver, Stern, Mutchler, Steffl, Merline, Buie, Spencer, Young, Young, 2006, Nature, 439

15 May 2005, frame 1 Notice the star trails, cosmic rays, chip gap…

15 May 2005, frame 2 Notice the star trails, cosmic rays, chip gap…

15 May 2005, frame 3 Dithering across the chip gap now…see anything?

15 May 2005, frame 4 Dithering across the chip gap now…see anything?

15 May 2005, sum 4 frames Looking for real objects among all the artifacts…

Hubble ACS image on 15 May 2005 Pluto Charon Hydra Nix

Pluto Charon Hydra Nix Hubble ACS image on 18 May 2005

15 and 18 May 2005, median 8 frames Hydra (P1) Charon Nix (P2) New moons are roughly 3-4x farther out than Charon, and co-planar with possible 6:4:1 orbital resonances

What does a “quadruple planet” look like? Animations produced with Celestia

NixHydra ~100 km Relative sizes of Pluto, Charon, and new moons 2300 km 1200 km The new moons are roughly 12x smaller and 600x fainter than Charon, and 4000x fainter than Pluto

Common origin of Pluto and all 3 moons: a giant impact ~4 billion years ago Similar to Earth-Moon formation?

The planet vote of 2006… and the reaction

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” 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) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as “Small Solar System Bodies”. Final Resolution 5 for GA-XXVI: Definition of a Planet 24 August 2006 Is Charon a satellite, or part of a binary dwarf planet ?

Nix Hydra …and Ceres are “dwarf planets”? Y Y Y Y ? ? Eris Dysnomia

Historical perspective: how many planets are there? Antiquity -- 7 planets in geocentric model (Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn) 1550 – 6 planets in heliocentric model (add Earth, remove Moon and Sun); the reaction was truly Medieval! 1781 – 7 planets (add Uranus) 1807 – 11 planets (add Ceres, Pallas, Juno, Vesta) 1845 – 12 planets (add Astraea) 1846 – 13 planets (add Neptune) 1851 – 8 planets (too many objects in Asteroid Belt to include them all – feeling any déjà vu yet?) 1930 – 9 planets (add Pluto) 1992 – Discovery of 1992 QB 1 …the Kuiper Belt! 2005 – Discovery of Eris (UB 313 ) 2006 – 8 planets (remove Pluto; don’t add Ceres, Charon, Eris or other “dwarf planets”)

Ceres Asteroid Belt Kuiper Belt Discovered Discovered in 1992…or 1930? Ceres and Pluto: The “ugly duckling” problem of being the first of an entire class

Inferring planets from extra-solar Kuiper Belt’s (vice versa): where planetary meets stellar astronomy Will our planet definition work for the other 6 billion planets in our galaxy ?

Ground-based Hubble Hubble undithered dithered High resolution images of Ceres reveal roundness, surface features, and colors

Ground-based Hubble Hubble undithered dithered High resolution images of Ceres reveal roundness, surface features, and colors

Three different faces of Ceres

Why does roundness matter ?

Differentiation of the asteroid Ceres as revealed by its shape Thomas, Parker, McFadden, Russell, Stern, Sykes, Young, 2005, Nature Letters, Vol 437

Jim Christy Annette and Patsy Tombaugh Jim Christy New Horizons launch 19 January 2006

DawnNew Horizons Pluto 2015 Vesta 2011 Ceres 2015

A “teachable moment” Pluto has not changed at all Classification is an important tool in science; imperfect, but allows us to move forward Progress is sometimes messy, the truth often seems counterintuitive at first – not determined by a vote Science is not a static body of facts, it is an ongoing process of discovery and debate

I’m delighted when Hubble inspires kids…

…because I was inspired