Cool Planets #1: Dwarf Planets

When I was young in the early 1960s, I loved planets, the solar system, space exploration, astronautsand anything astronomy. I watched the Mercury, Gemini and Apollo space capsule launches, including the moon landings. But our knowledge was rudimentary then.

It seemed simple. There were nine planets. Jupiter had twelve moons, Saturn had nine. But none of that is true anymore, as this blog will gradually reveal. NOW...

• There are eight planets and five dwarf planets.
• The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
• The five dwarf planets are Ceres, Pluto, Haumea, Makemake and Eris. Cool!
  
• Poor Pluto was recently demoted from planet to dwarf planet.
• To be a planet or dwarf, an object must orbit the Sun and be massive enough to have become rounded by the pull of its own gravity.
  
• To graduate from dwarf to planet, an object must have cleared its neighboring regions of small objects. (The dwarf planets still have debris in their orbital space.

Where are these dwarf planets?

• Ceres is in the asteroid belt (between the orbits of Mars and Jupiter). It has about one-third of the mass of the entire asteroid belt, just by itself. Yow!
• Pluto, Haumea and Makemake are in the area beyond the orbit of Neptune, in what is called the Kuiper Belt.
• Eris, the largest of the (current) dwarf planets orbits nearly three times the distance from the Sun as Pluto, Haumea and Makemake. This is beyond the Kuiper Belt in what is called the Scattered Disk.

Sedna is likely to qualify as a dwarf planet based on its size. But it is so far away, astronomers haven't been able to make the call about its shape. It is beyond the Scattered Disk and is called a "Detached Object".

This all wows me. How cool is it that they keep discovering new planetoids? And that there are whole bands or regions of the Solar System beyond Pluto that they are just discovering and naming?

This makes it fun for kids and kid-like objects (like myself). Never fear, there is plenty of stuff for us to discover when we grow up to be astronomers, amateur or professional.

In fact, a NASA probe is headed to meet Ceres in 2015. Stay tuned!

Learning science is fun! Science fun! Fun science!