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

Shortly after the discovery of Uranus, the Orbit of Uranus (as predicted by Kepler’s & Newton’s Laws) seemed off…!

Again using Gravitational Deflections, of Kuiper Belt Objects, to look for a new 9th Planet...!

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

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

Pluto’s Orbital Inclination out of the Ecliptic Plane

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

The Five (currently) known Moons of Pluto…!

Pluto is Not as Big as we first thought!

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

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

Pluto’s Friends…

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!

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

& Rabinowitz discovered Sedna! Then in 2003, 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”!

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!

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

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

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!

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

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

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

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

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