By Mike Hubbartt, © Copyright 2011, All Rights Reserved.

Dwarf Body Facts:

  • Number of Dwarf Planets: 5
    • Ceres
    • Eris
    • Haumea
    • Makemake
    • Pluto
  • Sizes: smallest is Ceres and the largest is Eris (maybe…)
  • Orbits: Ceres is in the asteroid belt between Mars and Jupiter, and the others are out around Pluto’s orbit (29-49 AUs)
  • Diameters: from 950 km to 2800 km
  • Total Number Moons for all dwarf planets: 7
    • Pluto’s Moons: Charon, Hydra, Nix, and P4
    • Eris’s moon: Dysnomia
    • Haumea’s moons: Hi’aka and Namaka
  • Interesting facts: Pluto will be visited by New Horizons in 2015, which will go on to explore the Kuiper Belt until 2022.
  • Click here for Wolfram|Alpha data on all Dwarf Planets

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1 Ceres (orbital period 4.6 yrs)

Ceres is located in the asteroid belt between Mars and Jupiter, and it was classified as an asteroid until 2006, when it was reclassified as a dwarf planet. Ceres is the smallest of the five dwarf planets and is located between Mars and Jupiter, making it a good candidate for a future mission if the data retrieved by the New Horizon mission is impressive. All we have to do is wait until 2015, when New Horizons should be within 186 miles of the surface of Pluto – we should get some impressive pictures at that time.

Click here for the Wolfram|Alpha information on Ceres

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136199 Eris  (orbital period 557.4 yrs)

Eris was discovered out past Pluto, and, due to it being slightly larger than Pluto, caused the discussions that eventually produced the new class of planetary bodies called Dwarf Planets. While I wish they added a 10th planet instead of cutting us down to 8, I understand that there may be a push to reconsider the decision to downgrade Pluto, since more recent measurements indicate Eris may be slightly smaller than Pluto. The atmosphere of Eris is currently frozen, so it is quite bright and there are photos from the Keck Observatory as well as from the Hubble that show Eris and its moon.

Click here for the Wolfram|Alpha information on Eris

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Dysnomia

Dysnomia is the only moon of Eris. Not a lot of data on it, except from JPL. Scientists used Dysnomia to measure the size of Eris, and Dysnomia makes a circular orbit around Eris once every 16 days.

Click here for the Wolfram|Alpha information on Dysnomia

==============================

136108 Haumea (orbital period 284.8 yrs)

Haumea was discovered in 2003, and its orbit ranges between 35 and 50 AUs, so it sometimes is closer to the sun than Pluto. It has a fast planetary rotation rate and its diameter averages 1400 km. It too has moons: Hi’aka and Namaka (not much data on either moon) in Starry Night or from JPL.

Click here for the Wolfram|Alpha information on Haumea

This image (Courtesy JPL/NASA) is an artist’s conception of Haumea and its two moons.

Courtesy NASA/JPL-Caltech

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136472 Makemake (orbital period 308 yrs)

Makemake (pronounced mah-kee-mah-kee) is larger than Haumea (average diameter of 1500 km) and the average distance from the sun is 46 AUs.

Click here for the Wolfram|Alpha information on Makemake
===========================

Pluto (orbital period 247.9 yrs)

Pluto was discovered by Clyde Tombaugh in 1930. I already wrote a short article about Pluto – click here to view it.

Click here for the Wolfram|Alpha information on Pluto

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Charon

Charon is the largest of Pluto’s 3 moons, but it was not discovered until 1978. Click here to see my earlier article on Pluto which has additional information on Charon.

Click here for the Wolfram|Alpha information on Charon

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Hydra

Charon is nearly as large as Pluto, but in 2005 it was learned that Pluto also has two tiny moons: Hydra and Nix. This is a screen shot of Hydra from Starry Night. Hydra has an estimated diameter of 20 – 70 miles.

Click here for the Wolfram|Alpha information on Hydra

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Nix

Nix is the other small moon of Pluto, and this is the Starry Night screen shot I found for Nix. Nix has an estimated diameter of 20 – 70 miles.

Click here for the Wolfram|Alpha information on Nix

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P4

P4 is the newest and smallest moon orbiting Pluto, with an estimated diameter of 8 – 21 miles.

Information Sources

NSAS’s website, NASA/JPL-Caltech’s website, Starry Night Pro Plus information, IAU Minor Planet Center.

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