Hubble Space Telescope

Max MutchlerSpace Telescope Science Institute

Friends School CollectionFebruary 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

19931997199920022008?

Installed during Hubble Servicing Mission 3B March 2002

Advanced Camera Advanced Camera for Surveys (ACS)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 PlutoHubble observations of Ceres and Pluto

What is a planet ?

Eris a

nd D

ysno

mia

The discovery of Pluto in 1930

ClydeTombaugh

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 ObservatoryWashington, 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, andco-planar with possible 6:4:1 orbital resonances

What does a “quadruple planet” look like?What does a “quadruple planet” look like?http://www.stsci.edu/~mutchler/pluto_50.html

Animations produced with

Celestia

NixNix

HydraHydra

~100 km~100 km

Relative sizes of Pluto, Charon, and new moons

2300 km 1200 km2300 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”.

http://www.iau2006.org

Final Resolution 5 for GA-XXVI: Definition of a Planet24 August 2006

Is Charon a satellite,

or part of a binary

dwarf planet ?

Nix

Hydra

…and Ceres are “dwarf planets”?

Y Y YY 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 QB1…the Kuiper Belt! • 2005 – Discovery of Eris (UB313)• 2006 – 8 planets (remove Pluto; don’t add Ceres, Charon, Eris or

other “dwarf planets”)

Ceres

Asteroid Belt Kuiper Belt Discovered 1801-1851 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

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 TombaughAnnette and Patsy Tombaugh

Jim Christy Jim Christy

New HorizonsNew Horizons launch launch19 January 200619 January 2006

http://www.dawn-mission.org http://pluto.jhuapl.edu

Dawn New Horizons

Pluto 2015

Vesta2011

Ceres2015

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…I’m delighted when Hubble inspires kids…

……because I because I was inspiredwas inspired