Transcript Four Great Satellite Observatories Hubble Space Telescope

The Dwarf Planet Pluto
http://en.wikipedia.org/wiki/Pluto
Dr. Harold Williams
Montgomery College Planetarium
http://Montgomerycollege.edu/Departments/planet/
Clyde Tombaugh
discover of Pluto
Lowell Observatory
Astrograph
Lowell Observatory
Blink Comparator
Ganymede (Jupiter), Titan (Saturn) and Callisto (Jupiter)
Io (Jupiter), Luna (Earth), Europa (Jupiter), Triton (Neptune)
and Pluto.
Asteroid Orbits
• Most asteroids orbit
in a belt between
Mars and Jupiter
• Trojan asteroids
follow Jupiter’s
orbit
• Orbits of near-Earth
asteroids cross
Earth’s orbit
Wikipedia Links
• http://en.wikipedia.org/wiki/Minor_planet
• http://en.wikipedia.org/wiki/Minor_Planet_Center
• http://en.wikipedia.org/wiki/Minor_planet_numbe
r
• http://en.wikipedia.org/wiki/Eris_%28dwarf_plane
t%29
• http://en.wikipedia.org/wiki/TransNeptunian_object
• http://en.wikipedia.org/wiki/Asteroid
• http://en.wikipedia.org/wiki/List_of_asteroids_na
med_after_important_people
Only a tiny number of
comets enter the inner
solar system - most
stay far from the Sun
Oort cloud:
On random orbits
extending to about
50,000 AU
Kuiper belt:
On orderly orbits
from 30-100 AU in
disk of solar system
How big can a comet be?
Pluto’s Orbit
• Pluto will never hit Neptune, even though their orbits
cross, because of 3:2 orbital resonance
• Neptune orbits three times during the time Pluto orbits
twice
Is Pluto a Planet?
•
•
•
•
•
By far the smallest planet.
Not a gas giant like other outer planets.
Has an icy composition like a comet.
Has a very elliptical, inclined orbit.
Pluto has more in common with comets than
with the eight major planets
Other Icy Bodies
• There are many icy
objects like Pluto on
elliptical, inclined
orbits beyond
Neptune.
• The largest of these,
“Planet X” was
discovered in
summer 2005, is
even larger than
Pluto
Kuiper Belt Objects
• These large, icy
objects have orbits
similar to the
smaller objects in
the Kuiper Belt that
become short period
comets
• So are they very
large comets or very
small planets?
What are the large objects of the
Kuiper belt like?
HST’s view of Pluto & Charon
What is Pluto like?
• Its moon Charon is nearly as large as Pluto
itself (probably made by a major impact)
• Pluto is very cold (40 K)
• Pluto has a thin nitrogen atmosphere that
will refreeze onto the surface as Pluto’s
orbit takes it farther from the Sun.
Other Kuiper Belt Objects
• Most have been discovered very recently so
little is known about them.
• NASA’s New Horizons mission will study
Pluto and a few other Kuiper Belt object in
a planned flyby.
Is “Planet X” a planet?
Pluto and “Planet X”
• Pluto’s size was overestimated after its discovery
in 1930
• It was considered a planet, and nothing of similar
size was discovered for several decades
• Now other large objects have been discovered in
Kuiper Belt, including “Planet X”
• Some scientists consider all of those objects
planets; others consider none of them planets.
Sedna in Green Circle
http://en.wikipedia.org/wiki/9037
7_Sedna
What have we learned?
• How big can a comet be?
– The Kuiper belt from which comets come
contains objects as large as Pluto.
• What are the large objects of the Kuiper
belt like?
– Large objects in the Kuiper belt have orbits
and icy compositions like those of comets.
• Is “Planet X” a planet?
– It remains a matter of opinion because
scientists have not yet settled on a definition
of the minimum size of a planet.
New Horizons Spacecraft
• http://en.wikipedia.org/wiki/New_Horizons
• Major Contractors JHU APL, SwRI
• New Horizons NASA’s Pluto-Kuiper Belt
Mission http://pluto.jhuapl.edu/
New Horizons
launched January 19, 2006
flyby Pluto July 14, 2015
Spacecraft New Horizons
Thermal Space Battery
Antennas of New Horizons (HGA,
MGA and LGA)