The document discusses the New Horizons mission, which was launched to explore the Pluto system and the Kuiper Belt, revealing new insights into celestial bodies within our solar system. It highlights the discoveries regarding Pluto's characteristics, its moons, and the implications for planetary classification, particularly addressing the challenges of current definitions set by the IAU. The document also emphasizes the ongoing shift in understanding the nature of planets, dwarf planets, and the classification criteria based on geophysical attributes rather than solely dynamical characteristics.

1. NNEEWW HHOORRIIZZOONNSS
First Exploration ooff TThhee PPlluuttoo
SSyysstteemm,, AAnndd TThhee KKuuiippeerr BBeelltt
BBeeyyoonndd
Alan Stern
Principal Investigator

5. MY FAVORITE
MISSION

6. NEW HORIZONS

7. HOWN DEIWD WHOE RGIEZTO TNOS DO
THIS?

8. WELL, THIS IDEA
DIDN’T WORK

9. PLUTO-CHARON:
BINARY PLANET
 Charon was discovered, by accident, in July 1978 by Jim Christy
of the U.S. Naval Observatory.
 Charon is in synchronous orbit ~17,000 km from Pluto; the
system is spin-spin-orbit-spin locked with a 6.4 day period.
 Charon’s surface is covered in crystalline H2O-ice and NH3-
hydrates and there is no detected atmosphere.
0.9 arc-sec

10. ROCKY/DIFFERENTIATED
From measured densities
and thermal evolution models
Pluto is a primarily
rocky, not icy body!
BODIES

11. COMPLEX
SURFACE
 N2 and CO ices
were discovered
in the 1990s.
 The CH4 and CO
distribution is
patchy.
 And N2 dominates
almost 10:1
HST Image

12. DISTENDED ATMOSPHERE,
HYDRODYNAMIC ESCAPE
 Detected in 1980s by refractive
signatures seen in stellar
occultations.
 Composed of N2, CO, and CH4,
plus trace species; there is good
evidence thermal structure and
for hazes.
 Base pressure is ~10 μbar.
 Likely escaping hydro-dynamically.
 Clearly changing since 1980s
with distinct structural and
pressure evolution.
 Possible Roche flow to
Charon.

13. A RICH
SATELLITE SYTEM
P4=Kerberos
P5=Styx

14. LONE MISFIT?
The Old View:
4 Terrestrial Planets
4 Giant Planets
1 Misfit Pluto

15. MISFIT NOT,
PLUTO’S ABOUND!
The New View:
4 Terrestrial Planets
4 Giant Planets
Perhaps 1000 Dwarf
Planets

16. THE REVOLUTION BROUGHT
BY THE KUIPER BELT
The New View:
Three-Zone Planetary
System
Planet Migration Proven
A Third Class of Planet
Found

17. THERE ARE SO MANY
PLANETS!

18. THE KUIPER BELT
CHANGED
EVERYTHING
Creating the Highest Funding Priority Medium-
Scale Mission New Start Of The Planetary
Decadal Survey
A Reconnaissance Expedition
To Pluto-Charon & the Kuiper Belt

19. SO WHEN NASA CALLED,
WE PROPOSED, AND WON

20. NEW HORIZONS!

21. SCIENTIFIC PAYLOAD
Instruments:
 REX radio science & radiometry
 RALPH VIS/IR imaging & spectroscopy
 ALICE UV imaging spectroscopy
 LORRI High-resolution imager
 SWAP plasma spectrometer
 PEPSSI energetic particle spectrometer
 SDC EPO Student Dust Counter

22. FASTEST SPACECRAFT
EVER LAUNCHED
227 ft

23. LAUNCH
19 JANUARY 2006

24. 2007: JUPITER
FLYBY
C/A Date 28 Feb 2007
Range 32 RJupiter
Jupiter science included studies of Jovian
meteorology, satellite geology and composition,
Auroral phenomena, and magnetospheric physics.

25. VOLCANOES AND
RINGS

26. COMPLETE
SUCCESS!
AND
A TREASURE
TROVE OF
NEW
SCIENCE

27. THEN 2007-2014:
ACROSS THE DEEP
PS-Hibernation
PS-Normal
PS-TCM
AS-Normal
AS-TCM
AS-EA
AS-SA
3A-Normal
3A-Encounter
3A-TCM

28. ENCOUNTER—2015!
 Jan-Mar: Observatory Phase
 April-June: Early Encounter
 July: Closest Approach
 Thru Late-2016: Downlink

29. PLUTO SYSTEM
AHOY!
Charon Detection by New Horizons July 2013

30. WE’VE BEEN PLANNING
THE ENCOUNTER
To Sun

31. WITH SIX
OBJECTS TO STUDY
P4=Kerberos
P5=Styx

32. AND TWO NEEDLES
TO THREAD
0.24°
Sun
Earth
Hydra
Charon
Pluto
Nix
Pluto C/A New Horizons Trajectory
11:50:00
13,695 km
13.78 km/s
Charon C/A
12:04:00
29,432 km
13.87 km/s
Pluto-Sun
Occultation
12:51:28
Charon-Sun
Occultation
14:17:50
Charon-Earth
Occultation
14:20:09
Pluto-Earth
Occultation
12:52:30 15:00
11:00
• S/C trajectory time ticks: 10 min
• Occultation: center time
• Position and lighting at Pluto C/A
• Distance relative to body center
Orbit Period a
Charon 6.4 d 19,571 km
Nix 24.9 d 48,675 km
Hydra 38.2 d 64,780 km
12:00
13:00
14:00

33. OVER A THOUSAND
OBSERVATIONS
Pluto global pan maps at 0.9 km/pix
Charon global pan maps at 0.9 km/pix
Pluto global IR at 9 km/pix
Nix global color maps at 2 km/pix
Charon global IR at 9 km/pix (+ pan at 0.6 km/pix)
Pluto global IR at 6 km/pix
Nix IR at 4 km/pix & pan at 0.3 km/pix
Pluto pan images at 0.4 km/pix
Charon IR at 5 km/pix (+ pan at 0.4 km/pix)
Charon global color at 1.4 km/pix
Pluto IR at 3 km/pix
Pluto global color at 0.7 km/pix
Nix pan at 0.5 km/pix
Pluto global pan at 0.5 km/pix, strip at 0.12 km/pix
Pluto pan at 0.3 km/pix, strip at 0.08 km/pix
Charon global pan at 0.6 km/pix, strip at 0.16 km/pix
Pluto (smeared) at 110 deg phase
Pluto radiometry at 230 km/pix
Pluto at 0.34 km/pix, 146 deg phase
Pluto in reflected Charonlight, 0.44 km/pix
Pluto solar and earth occultation
Plasma roll
Charon solar and earth occultation
•Timeline addresses all group 1 (required) and 2
(strongly desired) goals, and all but one group 3
(desired) goal.
•All group 1, and most of group 2 and 3 are addressed
redundantly
•P-21 days to P+6 days has already been sequenced and
reviewed by the science team.

34. WHAT WILL
WE FIND?

35. AT CURRENT
PLUTO RESOLUTION...

36. ONE CAN’T PREDICT
THE REAL THING

37. WE HAVE
NO IDEA
Triton from Voyager

38. SURPRISES
LIKELY AWAIT

39. SO WE EXPECT
DRAMATIC RESULTS
Triton & Pluto
At Best HST
Resolution
Triton from Voyager
The most exciting
discoveries will likely be
the ones we don’t anticipate.

40. HAVE A LOOK!
July 14, 2015 2:00 (P-10h) Highest Resolution 70m/px

41. THEN ON TO KBOs
2017-2021

42. NEW HORIZONS
VIDEO TRAILER

43. ONLY AMERICA
CAN DO THIS

45. Backup Charts

46. NEW HORIZONS
LAUNCH VIDEO

48. ARE YOU KIDDING?
If Earth were at
40 AU, it would
not be an IAU
planet!
Planets: Capable of
Clearing
Not Capable of
Clearing

49. Just As Some Stars Are
Stern/March
Small
and Some Are Very Large

50. Stern/March
RECENT TRENDS
IN PLANET
CLASSIFICATON
Two Broad Themes Have Been
Advanced:
1. Dynamical— i.e., Location
Based.
2. Intrinsic— i.e., Attribute
Based.

51. Stern/March
OR DO WE BASE THAT
ON ITS LOCATION?

52. SO DISCOVERING PLUTO
LED TO THREE SEPARATE
Discovery of The KuRipEeVr BOeLltU—TThIOe TNhSird
Largest Zone of Our Planetary System.
Stern/March

53. Stern/March

54. Stern/March

55.  Is also parallel to the definition of stars in
ways that unifies planet classification with
other astronomical bodies:
 1. Stars are stars based on a single
unifying attribute (ability to burn
elements by fusion), without regard to
orbit or location or size.
 2. The ability to do fusion is
fundamentally a gravitational criterion
varying only with regard to composition.
Stern/March
THE GEOPHYSICAL
PLANET DEFINITION

56. Stern/March
And
So, So Much More

57. Some Planets Are Small,
Some Are Freakishly
Large

58. Including
Hot Jupiters

59. Including
Pulsars with Planets

60. And Systems
With Highly Eccentric
Orbits

61. And Even Super Earths
& Balsa-Wood Density
Giants OGLE-2005-BLG-390Lb is a “super-Earth” extra-solar
planet, weighing 5.5 Earth masses.
And TrES-4 is 84% the
mass of Jupiter but with
an average density of
only about 0.24 gm/cm3.

62. WHAT’S SO ATTRACTIVE
ABOUT THE GPD
DEFINITION?
 It’s simple, intuitive, and far less ambiguous.
 It embraces a diversity of planetary sizes
and types which share a fundamental
physical trait in common: shape controlled
by gravity rather than material strength.
 It does not rely on having a complete census
of a system to classify its objects.
 Objects do not reclassify based on orbital
location.
 Instead, objects are classified purely on the
basis of their nature, as are stars, stellar
remnants, etc.

63. Science Reaches
Consensus
One Person at a Time

64. Copernicus Is Watching
Stern/March
Just Remember,
Nicolaus
Copernicus
1473-1543

65. So, Then: What Sets Small
Planets Apart From Large Ones?
 They are
smaller and more
numerous than
larger planets.
 Often their
orbits are more
elliptical and/or
more inclined.
But that’s about
it.

66. And What Do Small Planets
 They are believed to have formed like Earth, Mars, &
Venus.
 They are made of rock and ice—as are both Earth
and Mars.
 Many have moons—like other planets.
 Many likely have cores—like all of the known larger
planets.
 Some have atmospheres—just like larger planets.
 Their surfaces are solid—again, like the terrestrial
planets.
 They are expected to have active surface geology &
even tectonics— as do the terrestrial planets.
Simply Put—Small Planets
Have No Distinguishing
Intrinsic Characteristics
From Larger Planets
Stern/March
Have
In Common with Larger
Cousins?

67. And What Do Small Planets
 They are believed to have formed like Earth, Mars, &
Venus.
 They are made of rock and ice—as are both Earth
and Mars.
 Many have moons—like other planets.
 Many likely have cores—like all of the known larger
planets.
 Some have atmospheres—just like larger planets.
 Their surfaces are solid—again, like the terrestrial
planets.
 They are expected to have active surface geology &
even tectonics— as do the terrestrial planets.
Simply Put—Small Planets
Have No Distinguishing
Intrinsic Characteristics
From Larger Planets
Except Their Size.
Have
In Common with Larger
Cousins?

68. In 2006 the IAU Voted
Controversial Planet Definition
1. A celestial body that: is in orbit around the Sun,
2. Has sufficient mass so that it assumes a
hydrostatic equilibrium (nearly round) shape,
and
3. Has "cleared the neighborhood" around its orbit.
A non-satellite body fulfilling only the first two of
these criteria is classified as a "dwarf planet",
whilst a non-satellite body fulfilling only the
first criterion is termed a "small solar system
body."

69. What’s The Problem
With Dynamical
Clearing?
 First, it has nothing to do with the
attributes and nature of the body.
 Worse, it depends on the stellar mass and
the system’s age: Mplanet
> ~G-3/4TsystemM*1/4
aplanet
9/4
 Which fundamentally biases against both
young and distant planets.
 Consider: A reordering the planets in our
system would change which objects are

70. AND WHERE IS THIS
HYDROSTATIC DIVIDING
LINE?
Planets: Capable of
HSE
Not

71. Stern/March
A Census Gives 20 Solar
Orbiting Planets, 2/3 of Which
Are Dwarfs
 The Terrestrials: Mercury, Venus, Earth, and Mars.
 The Giants: Jupiter, Saturn, Uranus, and Neptune.
 The Rocky & Icy Dwarfs: Ceres, Pallas, Juno, Vesta,
Pluto, Charon, Quaoar, Ixion, EL61, Eris, Makemake,
and Sedna.

Science Is About
Discovering
New Paradigms

73. EXTRASOLAR PLANETS
ABOUND

76. IAU PLANET
DEFINITION
1. A celestial body that: is in orbit around the Sun,
2. Has sufficient mass so that it assumes a
hydrostatic equilibrium (nearly round) shape,
and
3. Has "cleared the neighborhood" around its orbit.
A non-satellite body fulfilling only the first two of
these criteria is classified as a "dwarf planet",
whilst a non-satellite body fulfilling only the
first criterion is termed a "small solar system
body."

77. IAU PLANET
DEFINITION
1. A celestial body that: is in orbit around the Sun,
2. Has sufficient mass so that it assumes a
hydrostatic equilibrium (nearly round) shape,
and
3. Has "cleared the neighborhood" around its orbit.
A non-satellite body fulfilling only the first two of
these criteria is classified as a "dwarf planet",
whilst a non-satellite body fulfilling only the
first criterion is termed a "small solar system
body."

79. Is It Really So Hard?
??????????????????????
Stern/March

80. Consider The Stark Trek Test
Stern/March

81. CLASSIFICATION
BY LOCATION IS
FLAWED

82. CLASSIFICATION
BY ATTRIBUTES
WORKS

83. CLASSIFICATION
BY LOCATION IS
FLAWED

84. ENTER
GPD
The “Geophysical Planet Definition”:
1. A celestial body that: has sufficient mass so
that it can assume a hydrostatic equilibrium
(nearly round) shape due to its gravity
overwhelming material strength.
2. But with insufficient mass to initiate sustained
fusion in its interior at any time.

85. WITH GPD:
ALWAYS A
PLANET