Pluto and the Dwarf Planets

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.

Planet vs. Dwarf Planet

WHAT IS A DWARF PLANET ANYWAYS?

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

IN OTHER WORDS…

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 Dwarf Planets

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

Ceres – 963 km across

The largest asteroid and smallest known dwarf planet

Pluto – 2,370 km across

The largest dwarf planet, has 5 moons

Makemake – 1,434 km across

Appears to be red in color

Eris – 2,326 km across

Almost as large as Pluto, has one known moon

Haumea – 1,920 km x 990 km across

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

Asteroid & Kuiper Belts

HOME OF THE DWARF PLANETS

Asteroid Belt

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.

Kuiper Belt

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

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References

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