Dwarf Planets

In our Solar System, there are currently five recognized Dwarf Planets with many more waiting to be discovered or confirmed. These are in order from Earth – Ceres, Pluto, Haumea, Makemake, and Eris. Like the other Planets these are all named after Gods and Goddess, although interestingly not just after Roman or Greek Gods.

When I was a child, I learned the order of the Planets by using this sentence – My Very Easy Method Just Speeds Up Naming Planets, with this rhyme I could easily remember them – Mercury, Venus, Earth, Jupiter, Saturn, Uranus, and Pluto. As we all know Pluto was downgraded from a Planet to a Dwarf Planet in 2006.

What exactly is a dwarf planet?

According to the International Astronomical Union, a Dwarf Planet is a celestial body that: –

  • Orbits the Sun
  • Has enough mass to assume a nearly round shape
  • Is not a moon e.g. they don’t orbit other planets or asteroids
  • Has not cleared the neighborhood around its orbit e.g. Pluto still has a lot of asteroids and other space rocks along its flight path around the Sun. Pluto hasn’t absorbed them over time like Earth or the other seven planets that orbit our sun have done.
Ceres – Photograph © NASA
Pluto – Photograph © NASA

The discovery of Makemake and Eris were in part responsible for Pluto becoming a Dwarf Plant.

Ceres – Goddess of the Harvest (Roman). Ceres is found in the Asteroid Belt between Mars and Jupiter, making her the only Dwarf Planet in the Inner Solar System. Ceres was originally classified as an asteroid but because Ceres is so much bigger and very different from her asteroid neighbors in 2006, she was upgraded to a Dwarf Planet.  Interestingly if it wasn’t for Jupiter’s gravity, she would have formed into a full Planet.

Pluto – God of the Underworld (Roman). American astronomer Clyde Tombaugh discovered Pluto in 1930 when he was twenty-four years old. Although he died in 1997 when Nasa launched the New Horizons probe in 2006 and began its nine-year journey to the edges of our Solar System some of his ashes were aboard. The temperature of Pluto is an icy -226 to -240 degrees Celsius. Pluto is smaller than our moon. He has an amazing heart-shaped glacier, blue skies, mountains, and the snow is amazingly red.

Haumea – Photograph © NASA

Haumea – Goddess of Fertility and Childbirth (Hawaiian). In Hawaiian mythology, Haumea’s children were created out of parts of her own body. Haumea’s two moons were thought to have been knocked off of her billions of years ago during a large impact and have been called Namaka and Hi’iaka after Haumea’s daughters. Haumea has an unusual oval shape. Astronomers think that she would have originally been like Pluto, comprised of rock and ice but that billions of years ago a large object may have collided with Haumea, knocking off most of the ice and causing her to go into a rapid spin. They think that this spinning may be what caused her unusual shape. She is one of the fastest rotating objects in the solar system completing a rotation every four hours.

Makemake – Photograph © NASA
Eris – Photograph © NASA

Makemake – God of Fertility (Rapanui). Makemake is the second brightest known object in the outer Solar System and takes 305 Earth years to orbit around the Sun.  As of now, we don’t know much about his surface as he is so far away but Makemake does appear to be similar to Pluto as it is a reddish-brown color. Scientists have also discovered signs of frozen methane and nitrogen on their surface.

Eris – Goddess of Strife (Greek). Eris is one of the largest of the Dwarf Planets and resides at the far edges of our Solar System. It takes Eris 557 Earth years to orbit around the Sun. Scientists think that she most likely has a rocky surface similar to Pluto. She has a small moon called Dysnomia, named after Eris’s daughter, the Demon of Lawlessness.

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