Pluto and the Dwarf Planets

Since its discovery in 1906, Pluto held the title of the 9th planet from the Sun. In 2006, Pluto was demoted after the discovery of 2 large planetoids orbiting nearby. The decision came down to adding 2 new planets or removing Pluto. In the end, it was decided that Pluto and the new planetoids should form a new group called the dwarf planets.

The main difference between a planet and a dwarf planet is that dwarf planets orbit within debris fields. Pluto lies within the Kuiper belt, similar to the asteroid belt in that there are a large number of objects orbiting within the same space.

The largest asteroid and smallest known dwarf planet

The largest dwarf planet, has 5 moons

Appears to be red in color

Almost as large as Pluto, has one known moon

Rotates once every 4 hours, so fast its shape is stretched into an oblong sphere. Two known moons.

Home to the dwarf planet Ceres which contains about a quarter of the entire mass of the asteroid belt. The asteroids are thought to be leftover material from a planet that failed to form due to gravitational disturbances from Jupiter.

The Kuiper belt lies beyond Neptune and appears to be doughnut-shaped. The rest of the dwarf planets reside here.

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http://www.astropa.unipa.it/HISTORY/hoskin.html

http://aa.usno.navy.mil/faq/docs/minorplanets.php

http://adsabs.harvard.edu/full/1946ASPL….5…73T

http://dawnblog.jpl.nasa.gov/2015/05/28/dawn-journal-may-28-2015/

http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150713

http://arxiv.org/abs/1402.4456

http://arxiv.org/abs/1304.1041v1

http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-137-8.pdf

http://solarsystem.nasa.gov/planets/profile.cfm?Object=Dwarf&Display=Sats

	Planet	Dwarf Planet
Orbits the Sun and isn’t a moon	✓	✓
Enough mass to hold a spherical shape	✓	✓
Orbital path is cleared of other objects	✓	✗

Pluto and the Dwarf Planets

Planet vs. Dwarf Planet

WHAT IS A DWARF PLANET ANYWAYS?

IN OTHER WORDS…

The Dwarf Planets

DON’T THINK OF IT AS LOSING A PLANET, BUT AS GAINING A DWARF PLANET (OR FIVE)

Ceres – 963 km across

Pluto – 2,370 km across

Makemake – 1,434 km across

Eris – 2,326 km across

Haumea – 1,920 km x 990 km across

Asteroid & Kuiper Belts

HOME OF THE DWARF PLANETS

Asteroid Belt

Kuiper Belt

Want to learn more about the Solar System?

References