Chapter 11: Part 1 Pluto and
the Dwarf Planets
Pluto: Ruler of the Underworld
Pluto was discovered by Clyde Tombaugh in 1930 by comparing one image of
the sky taken one night with an image taken 6 nights later.
The discovery of Charon
Charon and Pluto
HST discovers new moons!
2012
New Horizons visits Pluto July 2015
Pluto revealed!
Pluto and Charon
What is Pluto?
• Strange object; located far out from the Sun
with gas giants but small size and very
elliptical and highly inclined orbit
• Pluto is a mixture of ices and rocks
• composition similar to satellites of giant
planets
• Could be captured Kuiper Belt Object (e.g.
comet)?
Pluto’s strange orbit
Quaoar, Sedna, Earth, Moon, and
Pluto size comparisons
th
10
Planet???
IAU Definition
A "planet" is a celestial body that:
(a) is in orbit around a star,
(b) has a nearly round shape
(c) and has cleared the neighborhood
around its orbit.
8 Planets !
Planets sweep up all the material along their orbit
Pluto’s strange orbit
Dwarf Planet Orbits are Strange
Dwarf Planet Definition
A “dwarf planet is” a celestial body that:
(a) is in orbit around the Sun,
(b) has a nearly round shape
(c) has not cleared the neighborhood
around its orbit and is not a satellite
5+ Dwarf Planets !