Transcript Lecture - Faculty

Planet Searching
• After Uranus and Neptune, some began
searching for yet another planet, among
them was P. Lowell from 1905-1916
• Search resumed in 1929 by C. Tombaugh,
who identified a candidate on 2/18/1930
• The name “Pluto” was suggested by an
English girl of age 11.
Discoveries: Pluto at left and
moon Charon at right
Clyde
Tombaugh
James
Christy
Hubble Image of Pluto & Charon
Pluto and Charon to Scale
Mapping Pluto
Charon’s orbit is such as to eclipse Pluto at
times, allowing us to map its surface
Done in 1985
HST mapped Pluto to a resolution of 150 km,
revealing a strong variation of reflectivity
Pluto-Charon Eclipses
Charon-Pluto Eclipse Visual
Surface Mapping with HST
A Map of Pluto
Pluto is ODD!
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Similar to Triton
Cold at T=50K
Has frozen CH4
Mostly rock and ice
Largest eccentricity, with
D ~ 30-50 AU (sometimes
closer than Neptune)
• Large orbital inclination
• Smaller than planets
• Large moon in relative size
Origin of Pluto-Charon:
• Pluto ejected from
Neptune – problem is
Charon
• Pluto and Charon formed
together (?)
• Pluto captured Charon
(?)
• Giant impact like EarthMoon system (?)
Orbits for Pluto and Neptune
Atmosphere of
Pluto
It is possible to study
Pluto’s atmosphere from
Earth using occultation of
starlight.
The light passes through
the tenuous atmosphere.
In this way we can “see”
the atmosphere.
Spectroscopy reveals composition
of Pluto and Charon
Charon
• Discovered in 1978 by J. Christy
• Has an icy surface of frozen N and tenuous CH4
atmosphere
• Orbital plane is nearly perpendicular to ecliptic
• In synchronous orbit with Pluto (and vice versa)
• Ratio of masses: MC/MP=0.13
• Ratio of sizes: RC/RP=0.51
• As seen from Pluto, Charon subtends an angle
of 4o, but the Sun is only 1’ !
Structure of Pluto and Charon
Synchronous Orbits for Pluto and
Charon
New Moons:
Nix, Hydra,
and “P4”
New Horizons
Dwarf Planets
A "dwarf planet" is a celestial body that, within the Solar
System:
1. is in orbit around the Sun
2. has sufficient mass for its self-gravity to overcome rigid
body forces so that it assumes a (near-spherical) shape
3. has not cleared the neighborhood around its orbit
4. is not a satellite
The term "dwarf planet" applies only to objects in the Solar
System and is distinct from "planet" and "small solar
system body".
Eris and moon Dysnmonia
(goddess of discord and daughter of
lawlessness)
Xena
Gabrielle
Orbit of Eris
Comparison of Pluto with Eris
Ceres is now a dwarf planet
that was previously the
largest of the asteroids. It
was discovered on Jan 1,
1801, by Giuseppe Piazzi.
With a diameter of about
950 km. Ceres is in the
asteroid belt, and it was the
largest and most massive
body there, but now is the
3rd of the dwarf planets.
Interestingly, it contains
approximately a third of the
belt's total mass.
Ceres
Rotation and Surface of Ceres
Interior of Ceres
Two Other Dwarf Planets
Haumea
Makemake
Future Dwarf Planets?