The Dwarf Planet Pluto& New Horizon

http://en.wikipedia.org/wiki/Pluto

Dr. Harold Williams

Montgomery College Planetarium http://Montgomerycollege.edu/Departments/planet/

Clyde Tombaughdiscover 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_number • http://en.wikipedia.org/wiki/Eris_

%28dwarf_planet%29 • http://en.wikipedia.org/wiki/Trans-

Neptunian_object • http://en.wikipedia.org/wiki/Asteroid • http://en.wikipedia.org/wiki/

List_of_asteroids_named_after_important_people

Kuiper belt:On orderly orbits from 30-100 AU in disk of solar system

Oort cloud:On random orbits extending to about 50,000 AU

Only a tiny number of comets enter the inner solar system - most stay far from the Sun

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”, now called Eris (it has a moon called Dysnomonia), 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.

Sedan in Green Circlehttp://en.wikipedia.org/wiki/9037

7_Sedan

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, Eris” 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 Horizonslaunched January 19, 2006flyby Pluto July 14, 2015

Spacecraft New Horizons

Thermal Space Battery

Antennas of New Horizons (HGA, MGA and LGA)

Comet Analogue

• Dry Ice, frozen Carbon Dioxide, CO2

• Water, H2O

• Builders sand, Silicates mainly SiO2

• Charcoal, largely Carbon, C• Dark Karo Syrup, complex hydrocarbons

• Little Ammonia, NH4

• Frozen Methane, CH4, not used for safety sake (it burns and explodes in air), but it looks like CO2

Time Line

• Launched January 19, 2006

• Jupiter Gravity Assist February 2007• flyby Pluto July 14, 2015