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Basics: Dwarf Planets

in: The Solar System

Author: Zhunoman

Created: 14th Feb 2022 (Edited: 1st Mar 2022)

Tags: Space Introductions Planets Moons Dwarf Planets

Dwarf planets are similar to normal planets with some differences. This blog will explain this in basic terms. 


Basics: Dwarf Planets

Main Image Credit (built from): NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Caltech/UCLA/MPS/DLR/IDA 

Dwarf planets are not so much different from other planets in certain ways. They are on average smaller, should be rounded, and may have moons. The main issue with classification is that they:

Do not clear the area around their orbit...

It is usually agreed that they should have enough mass and gravity to be (more or less) rounded in shape. They are not moons, although certain well known dwarf planets have moons orbiting them. Pluto has at least 5.

Currently in our solar system there are 5 well known dwarf planets. The number is growing, but it is not always certain which ones have been 100% confirmed.  The most well known dwarf planet is Pluto, because it used to be considered a planet (for a very long time). 

Out of the 5 known dwarfs, except for Ceres, 4 of them are located in the far out region called the Kuiper belt. It starts at around the same orbit as Neptune (about 30 AU), and extends for 20 AU in width from that point (remember that 1 AU is the distance of Earth from the Sun). Ceres is located, even closer to the Sun than Jupiter, in the asteroid belt region.

The following is a brief overview of the 5 best known dwarf planets: Pluto, Ceres, Makemake, Haumea, and Eris. Only Pluto and Ceres have good quality real photos. The rest have only small images or artist impression drawings. To see the full article, click on the link (work in progress).

 

Pluto

As of year 2022, Pluto has been known for almost 100 years (discovered 1930). It is very far out in the solar system. It is smaller than Earth’s moon. For years it was considered a planet, but then it got demoted to dwarf planet (much to the chagrin of many people!) It was the first astral body to be given this categorization. It has 5 known moons. Image: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute:

pluto

 

Ceres

This is the only dwarf planet known to be located in the inner solar system. It is not far from Earth; it is closer to us than Jupiter. For a long time it was considered an asteroid. In 2006 it was reclassified as a dwarf. Although Pluto was the first to be called a dwarf, Ceres was actually discovered first (in 1801). It has no known moons. Image: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Ceres

 

Makemake

This oddly named dwarf is a relatively recent discovery. It was found in 2005. There are currently no good real photos of Makemake, it is extremely far out. It is said to be slightly smaller than Pluto. It has no confirmed moons at this time (check blog date!) Provisionally, it is said to possibly have 1 moon, but this is awaiting confirmation.

 

Haumea

This is another dwarf similar in size to Pluto. Haumea was discovered in 2003. It shares a similar orbit distance to Makemake. It has a rounded shape but is not spherical. It looks similar to an American/ Rugby football, or possibly more like an egg shape (but not quite). It is considered one of the fastest rotating larger objects in the solar system. It has 2 confirmed moons to date.

 

Eris

This dwarf is extremely far out. It is about the same size as Pluto, but slightly smaller. It is the second largest known dwarf, but it is more massive than Pluto. For this reason, it is the 9th most massive object orbiting the Sun as of writing this blog. It has one small moon called Dysnomia. Image (artist impression): NASA/JPL-Caltech, Published: 2011-April-11

Eris

 

Further reading

https://www.jpl.nasa.gov/infographics/what-is-a-dwarf-planet

https://en.wikipedia.org/wiki/Dwarf_planet

https://spaceplace.nasa.gov/planets-round/en/

https://solarsystem.nasa.gov/planets/dwarf-planets/pluto/overview/

https://solarsystem.nasa.gov/planets/dwarf-planets/ceres/overview/

https://solarsystem.nasa.gov/planets/dwarf-planets/makemake/in-depth/

https://solarsystem.nasa.gov/planets/dwarf-planets/haumea/in-depth/

https://solarsystem.nasa.gov/planets/dwarf-planets/eris/in-depth/