Planets, Dwarf Planets and Moons In Our Solar System

Planets, Dwarf Planets and Moons In Our Solar System

- in Science & Tech

When we think about the solar system, the first thought is that the largest body is the Sun. Next are the planets, then the moons, asteroids and comets.  This is mostly true, but not exactly. We know that there are  7 moons larger than Pluto and 2 moons that are even larger than Mercury! When astronomer Mike Brown “The Pluto Killer” and his team discovered the celestial body – Eris – in January of 2005′ our perspective of what is going on in the solar system changed quite a bit.

It opened up our minds to a new way of understanding the Solar system. In 2005′, Eris was thought to be bigger than Pluto. Astronomers and scientists around the world were stumped. Should they make Eris a 10th planet? Or should they downgrade Pluto to not a planet at all.

In 2006′, the choice was made to create a new class of celestial objects called “dwarf planets”. The only difference between a planet and a dwarf planet is the area surrounding each celestial body. A dwarf planet has not cleared the area around its orbit, while a planet has. Pluto and Eris became the first two dwarf planets.

Source: NASA

Since 2005′, three more major dwarf planets have been identified in our solar system named Ceres, Haumea and Makemake. Ceres was found within the asteroid belt, not too far from Earth when looking at the scale of the solar system. The other definite dwarf planets were discovered far out by the Kuiper belt, a part of the solar system that begins beyond the orbit of Neptune (30 Astronomical Units) and extends out to 50 AU. One AU is the distance from the Sun to the Earth which is about 93 million miles.

The Kuiper belt is thought to contain many asteroids, comets, and smaller icy bodies. Another six bodies in our solar system are almost definitely dwarf planets. Astronomers believe there may be as many as 200 dwarf planets in the Kuiper belt alone and more than 10,000 dwarf planets in our solar system when we go beyond the Kuiper belt. To help understand, here is the distance of each planet and dwarf planet from the sun.

Mercury  0.39 AU

Venus  0.72  AU

Earth  1 AU

Mars  1.52 AU

Ceres 2.77 AU

Jupiter  5.20 AU

Saturn 9.58 AU

Uranus 19.20 AU

Neptune  30.05 AU

Pluto  39.48 AU

Haumea 43.13 AU

Makemake 45.79 AU

Eris 68.01 AU

one AU is 93 million miles

Another thing that is incredible is that there are 7 moons in our solar system that are bigger than the biggest known dwarf planet, Pluto.  And there are 2 moons bigger than Mercury! Here is a list of the largest objects in our Solar System by diameter.

An illustration of the solar system to scale, created by the San Francisco-based artist Roberto Ziche. The image features the Sun in the background with the planets, Moon and the four dwarf planets lined up in the foreground in relative scale of size to one another.

Sun 1,392,000 km

Jupiter 142,984 km

Saturn 120,536 km

Uranus 51,118 km

Neptune 49,528 km

Earth 12,756 km

Venus 12,102 km

Mars 6,796 km

Ganymede 5,262 km    -Moon of Jupiter

Titan 5,150 km              -Moon of Saturn

Mercury 4,880 km

Callisto 4,806 km          – Moon of Jupiter

Io 3,642 km                    – Moon of Jupiter

Moon 3,474 km

Europa 3,120 km          – Moon of Jupiter

Triton 2,706 km           -Moon of Neptune

Pluto 2,370 km

Eris 2,326 km


There are 194 identified moons in our solar system and there may be a whole lot more. Mercury, Venus and Ceres do not have moons. Earth has 1, Eris has 1, Makemake has 1, Mars has 2, Haumea has 2, Pluto has 5,  Neptune has 14, Uranus has 27, Saturn has 62 and Jupiter has 79.

Between 1999′ and 2003′ astronomers found 34 moons of Jupiter. 15 more of Jupiter’s moons were discovered from 2003-2015 and 2 more in 2016′. On July 17, 2018, 10 more moons of Jupiter were announced bringing us to the current total of 79 moons of Jupiter!

There is so much going on in our solar system alone. And this is nothing compared to the hundreds of billions of stars in our galaxy and over a hundred billions galaxies in our Universe.  In the next article I will write about Planet Nine, the theorized planet in our solar system that is thought to exist due to an unknown force causing numerous celestial bodies to orbit the sun on a totally different angle than the known planets. It is theorized to be 10X larger than Earth based on mathematical calculations.

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