Download Pluto_Friends

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
1993
1997
1999
2002
2008?
Advanced Camera
for Surveys (ACS)
Installed during
Hubble Servicing Mission 3B
March 2002
The “Home of Hubble”
Space Telescope Science Institute (STScI)
on the campus of Johns Hopkins University in Baltimore
Hubble observations of Ceres and Pluto
What is a planet ?
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
Notice the star trails, cosmic rays, chip gap…
15 May 2005, frame 1
Notice the star trails, cosmic rays, chip gap…
15 May 2005, frame 2
Dithering across the chip gap now…see anything?
15 May 2005, frame 3
Dithering across the chip gap now…see anything?
15 May 2005, frame 4
Looking for real objects among all the artifacts…
15 May 2005, sum 4 frames
Hydra
Nix
Charon
Pluto
Hubble ACS image on 15 May 2005
Hydra
Nix
Charon
Pluto
Hubble ACS image on 18 May 2005
New moons are roughly 3-4x farther out than Charon, and
co-planar with possible 6:4:1 orbital resonances
Hydra (P1)
Charon
Nix (P2)
15 and 18 May 2005, median 8 frames
What does a “quadruple planet” look like?
http://www.stsci.edu/~mutchler/pluto_50.html
Animations
produced with
Celestia
Relative sizes of Pluto, Charon, and new moons
Nix
Hydra
2300 km
1200 km
~100 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
http://www.iau2006.org
Final Resolution 5 for GA-XXVI:
Definition of a Planet
24 August 2006
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”.
Dysnomia
…and Ceres are “dwarf planets”?
Nix
Y
Y
Y
Hydra
Eris
Y
?
?
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 and Pluto: The “ugly duckling”
problem of being the first of an entire class
Asteroid Belt
Kuiper Belt
Discovered 1801-1851
Discovered in 1992…or 1930?
Ceres
Inferring planets from extra-solar
Kuiper Belt’s (vice versa): where
planetary meets stellar astronomy
Ground-based
Hubble
undithered
Hubble
dithered
High resolution images of Ceres reveal
roundness, surface features, and colors
Ground-based
Hubble
undithered
Hubble
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
Annette and Patsy Tombaugh
Jim Christy
Jim Christy
New Horizons launch
19 January 2006
Dawn
Ceres
2015
New
Horizons
Pluto
2015
Vesta
2011
http://www.dawn-mission.org
http://pluto.jhuapl.edu
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