How Many Planets Are There? School Day's Question Has Changing Answers

I remember being in school and the teacher asking, "How many planets are there in the solar system?" The answer was always the same, nine. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto; these names were known by every school child in America. I cannot speak for other countries, not having gone to grade school anywhere other than Breese, Illinois.

A couple years ago, my youngest daughter came home from school and let us knows that there were only eight planets in our solar system. I had read in the newspapers, online, watched on television, and heard on the radio all the fervor over the dismissal of Pluto as a "planet". Suddenly our solar system no longer had nine planets, it only had eight. The whole universe as we knew it was wrong. References to the nine planets in textbooks, novels, science fiction, everything we knew since the 1930 discovery of Pluto was wrong. Why? Was it really necessary? Couldn't the "great minds" of our civilization come up with something better than demoting Pluto?

Pluto had always been Planet X. Astronomers in the 1840s speculated about another planet beyond Uranus. After the discovery of Neptune, astronomers predicted in the 1890s that there was another planet, Planet X, causing a gravitational pull on Neptune other than Uranus. When it was discovered in 1930, the planet's name was ultimately chosen by an 11-year old school girl, building on the tradition of naming heavenly bodies after mythological beings, as one of the alternate names of the Greek God of the Underworld, Hades. The director of the Lowell Observatory in Arizona was given the honor of naming the planet and chose the little girl's suggestion, since the planet was such a cold and dark place due to it's distance from the sun.

Pluto existed in our minds. It became the name of Walt Disney's lead character Mickey Mouse's dog. Pluto became a part of Americana. In the 1970s gave Pluto its first moon, named Charon. 2005 brought two more moons; Nix and Hydra. Pluto was a full-fledged member of the Solar System, as we knew it. Why did it go wrong? The International Astronomical Union (IAU) decided that three factors had to exist for an object to be classified as a "planet". That decision led to some planets being dropped or re-classified. It had went on before, there's nothing new under the Sun. Ceres was discovered in 1801 as a planet between Mars and Jupiter. For fifty years it was in textbooks, novels, and the like as a planet. It was dropped from that status but because of the IAU it is now considered a "dwarf planet", the only one that is in the Solar System Asteroid Belt. So, in reality we have eight planets and two dwarf planets for a total of ten planets. Right? But wait, there's more.

Since the decision in 2006, more planets and heavenly bodies have been added. There's the dwarf planet Varuna, founded in 2000, and named for a Hindu God of the Ocean. In 2002 the dwarf planet of Quaoar, named for the Native American Tongva Indian Creator God, was found and the next year the dwarf planet Sedna, named for the Inuit Goddess of the Sea, was found. All three of these are still up for consideration by the IAU for dwarf planet status. Haumea, named for the Goddess of the Hawaiian island, was founded in 2004 and under the 2006 rules classified as a dwarf planet. In 2005 the planet, Eris was discovered and in 2006 was classified as a dwarf planet. This planet, named after Greek Goddess of Strife, is the largest dwarf planet in our Solar System, larger than Pluto. Our final planet, Makemake, was also discovered in 2005 and named for the Creator of Humanity from the Rapanui people, who were native to Easter Island It is also the third largest dwarf planet in our Solar System.

So, by the current standards, our Solar System really has sixteen planets. I guess what the IAU did, instead of limiting our Solar System have helped it to grow. Below I've listed our planets in their order from the Sun. The standard used to discuss bodies in the Solar System is AU, a term which mean "astronomical unit" and which equals 93 million miles, the distance from the Earth to the Sun. For example, Pluto is 39.48 AU from the Sun or over 3 billion miles away. Quaoar comes in at 43 AU, Varuna-43 AU, Haumea-50 AU, Makemake-52 AU, Sedna-89.6 AU, and Eris-96.7 AU.

1. Mercury

2. Venus

3. Earth

4. Mars

5. Ceres

6. Jupiter

7. Saturn

8. Uranus

9. Neptune

10. Pluto

11. Quaoar

12. Varuna

13. Haumea

14. Makemake

15. Sedna

16. Eris

Information on dwarf planets and their distance from the Sun was gathered from International Astronomical Union website at www.iau.org.