1. The “Not-Quite-Planet” Pluto
…and Friends!

2. Pluto’s Orbital Eccentricity (Elliptical Orbit, ~30-50 AU from Sun)

3. How to Survive a Neptune-Crossing Orbit:
 A 3:2 Resonance between Neptune and Pluto
(& various other “Plutinos”!)

4. Pluto’s Orbital Inclination out of the Ecliptic Plane

6. Charon: Ferryman of the dead
over the River Styx, into Hades…

7. The Five (currently) known Moons of Pluto…!

10. Pluto is Not as Big as we first thought!

12. Pluto is Cold! (=< 40 K ~ -387o F!)

14. Gorgeous Pluto! The dwarf planet has sent a love note back to Earth via our New Horizons spacecraft, which has traveled more than 9 years and 3+ billion miles. This is the last and most detailed image of Pluto sent to Earth before the moment of closest approach, which was at 7:49 a.m. EDT Tuesday - about 7,750 miles above the surface -- roughly the same distance from New York to Mumbai, India - making it the first-ever space mission to explore a world so far from Earth. This stunning image of the dwarf planet was captured from New Horizons at about 4 p.m. EDT on July 13, 2015, about 16 hours before the moment of closest approach. The spacecraft was 476,000 miles (766,000 kilometers) from the surface. Images from closest approach are expected to be released on Wednesday, July 15. Image Credit: NASA #nasa #pluto #plutoflyby #newhorizons#solarsystem #nasabeyond #science312k likes11.8k comments

19. Pluto’s Friends…

20. The “Kuiper” (or “Edgeworth-Kuiper”) Belt:
Hypothesized for decades after Pluto’s Discovery in 1930…
…not discovered until 1992 (“1992 QB1”) by David Jewitt & Jane Luu!

21. New Kuiper Belt Object (“K.B.O.”) discovered by Trujillo & Brown
in 2002: “Quaoar”! (…named after the Tongva creator god…)

24. & Rabinowitz discovered Sedna!
Then in 1993, Brown, Trujillo,
& Rabinowitz discovered Sedna!
(…named after the Inuit goddess of the sea, living at the bottom of the frigid Arctic Ocean…)
 Because Sedna then became
“the coldest most distant place
known in the Solar System”!

29. Q: Why is Pluto no longer defined as a “Planet”?
The Currently Official Definition of a Planet:
(…after many different ideas
proposed, criticized, & rejected!)
But this condition
can be ambiguous;
why even bother with it…?
(…what’s the key motivation for
deliberately demoting Pluto?)
Pluto Demotion Vote
by the International
Astronomical Union (IAU)
on August 24, 2006!

30. If Pluto Stays a “Planet”, then How Many More Solar System Objects
will have to Become “Planets”? (esp. Newly-Discovered Objects!)

32. The “final straw” for Pluto’s Planet Status: Eris Discovered in Jan

33. Eris: Was the first known Kuiper Belt Object Larger than Pluto!
Time for a
Planetary
Comeback…?
Until: The New Horizons mission images in July 2015 upgraded
Pluto’s diameter to 2,370 km… 34 km Bigger than Eris!

35. IAU (Mythological) Naming: Eris: Greek Goddess of
Chaos, Strife, & Discord!
(and daughter of Nyx)
(…and Eris’ moon…):
Dysnomia: Eris’ Daughter,
Greek goddess of Lawlessness!

36. Lawless  Lucy Provisional Naming: Eris & Dysnomia were first
(unofficially) known as “Xena” & “Gabrielle”…
 Lucy
Lawless

37. Should we have kept Pluto a “Planet” out of Historical Tradition?

38. Counting the Planets… According to History…
In Antiquity:
(Geocentric
Universe!)
1) Sun
2) Moon
3) Mercury
4) Venus
5) Mars
6) Jupiter
7) Saturn
________ 7
Copernicus (1543):
(Heliocentric
Solar System)
1) Mercury
2) Venus
3) Earth
4) Mars
5) Jupiter
6) Saturn
________ 6
Herschel (1781):
1) Mercury
2) Venus
3) Earth
4) Mars
5) Jupiter
6) Saturn
7) Uranus
________ 7
Piazzi (1801):
(Asteroids!)
1) Mercury
2) Venus
3) Earth
4) Mars
5) Ceres
6) Pallas
7) Juno
8) Vesta
9) Jupiter
10) Saturn
11) Uranus
________ 11
Adams &
LeVerrier
(1846):
1) Mercury
2) Venus
3) Earth
4) Mars
5) Jupiter
6) Saturn
7) Uranus
8) Neptune
________ 8

39. 8 8 9 12+ Counting the Planets According to History (continued…)
Adams &
LeVerrier
(1846):
1) Mercury
2) Venus
3) Earth
4) Mars
5) Jupiter
6) Saturn
7) Uranus
8) Neptune
________ 8
Tombaugh
(1930):
1) Mercury
2) Venus
3) Earth
4) Mars
5) Jupiter
6) Saturn
7) Uranus
8) Neptune
9) Pluto
________ 9
IAU
(8/16/2006):
1) Mercury
2) Venus
3) Earth
4) Mars
5) Ceres
6) Jupiter
7) Saturn
8) Uranus
9) Neptune
10) Pluto &
11) Charon
12) Eris…
________
12+
IAU
(8/24/2006):
1) Mercury
2) Venus
3) Earth
4) Mars
5) Jupiter
6) Saturn
7) Uranus
8) Neptune
Pluto
________ 8
“Even though I lost Eris
as the tenth planet,
I suddenly realized
that I had an opportunity
to actually make a
scientific definition of the
word ‘planet’ that described the
solar system correctly.”
-- Mike Brown,
co-Discoverer
Of Eris
The dwarf planet Pluto is recognised as an important prototype of a new class of Trans-Neptunian Objects... “plutoids”
-- IAU, 6/11/2008