Sucks to be Pluto

The moment I finished the space odyssey, I began getting grief about not including Pluto. Sorry friends, but Pluto is not a planet. Sure it used to be, but it was downgraded. Like most other scientists I have to agree that it doesn’t deserve to be in the same class as bodies like Jupiter and Saturn.

The International Astronomical Union (IAU) is who started the drama around Pluto. They are the big shot organization that controls how we think about space. They are also the ones with the authority to name heavenly objects.

The drama started in January 2005 when Eris (official name: Eris 136199) was discovered. Eris was found orbiting out past Pluto in the Kuiper Belt. It was determined to be 27% more massive than Pluto. NASA started calling Eris the tenth planet and got excited about the high probability of finding more planets, but the IAU had something to say about that.

In August 2006, the IAU held a meeting in Prague and passed Resolution 5A. This resolution established guidelines to determine if something is a planet or a dwarf planet.

To be a planet, an object must:
1. Orbit the sun
2. Be large enough to produce enough gravity to make itself (mostly) round
3. Clear the neighborhood around its orbit

To be a dwarf planet, an object must:
1. Orbit the sun
2. Be large enough to produce enough gravity to make itself (mostly) round
3. Not have cleared the neighborhood of its orbit
4. Not be a satellite (moon)

All other objects (i.e. comets, asteroids, etc) are classified collectively as “Small Solar System Bodies”.

Pluto is tiny (only about 70% the size of our moon), but it is able to meet requirements one and two of being a planet. The problem lies in requirement three. Pluto orbits in the Kuiper Belt (basically the same thing as the asteroid belt, just a little larger. It starts right outside the orbit of Neptune). A true planet would have cleared the belt out of its orbit, but Pluto did not.

Picture from http://www.mathiaspedersen.com/

Just like that, Pluto got its planet card revoked. Our solar system only contains 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune). In Resolution 6A, Pluto was officially named a dwarf planet as well as the prototype for a new variety of trans-Neptunian objects, which (according to Resolution 6B) will be called “Plutonian Objects”.

Now Pluto gets to hang out with the other dwarfs, like Ceres and Eris.

Whatever, I would rather hang out with them anyway!

Robert’s Out of This World Space Odyssey: Saturn, The Diva

When Galileo was just sitting on his balcony, having a lovely glass of limoncello, nibbling on a cannoli and looking into the havens through his telescope, he saw the 6th planet from the sun. This is the last planet anyone on Earth will be able to see with a naked eye. As Galileo sketched the planet, he noted two spheres on either side of the main body. He drew them on as handles attached to the planet and assumed this planet must be a triple-bodied system. Not until Dutch astronomer Christiaan Huygens came along in 1659 did the world realize that this planet was actually surrounded by thin rings. Now Saturn and her rings is the most recognizable planet in our solar system.

Saturn (named after the Roman god of agriculture) is the second largest planet in the Milky Way. Much like Jupiter, Saturn is a gas giant comprised mostly of hydrogen and helium, with a possibility it may have a solid rocky core. Saturn has earned the title of least dense planet. It is 1/10 the density of Earth and 2/3 the density of water. If you could put Saturn in a giant bucket of water, it would float.

This ball of gas can whip around the sun once every 10,759 Earth days. That means one year on Saturn is equal to 29.5 Earth years. One day on Saturn (a full rotation around its axis) takes 10 hours 39 minutes – just a little slower than Jupiter.

The weather on Saturn is also comparable to Jupiter. Saturn has layers of various gasses at different temperatures that give the presence of colorful cloud bands covering the planet. High winds keep the clouds moving.

Everyone knows Saturn because of her rings. Rather than one giant ring, Saturn has a system of rings that rotate around the equator and never touch the planet. Narrow ringlets of ice and rock particles (ranging in size from a grain of sand to the size of a house) come together to form the 7 major rings of Saturn. The particles are believed to come from asteroids, comets and pieces broken off of Saturn’s moons. The rings rotate at various speeds and can reach widths of almost 180,000 miles (300,000 kilometers) across. They may be wide, but they are not thick – they vary from 660 to 9,800 feet (200 to 3,000 meters). In some places the rings may only be as thick as a tall person. There are also several gaps in the rings, with the largest (the Cassini Divide) being 4,800 kilometers (3,000 miles) wide. This gap is caused by the gravitational force of one of Saturn’s moons, Mimas.

Saturn has 53 naturally orbiting moons. The moons are all uber interesting – some actually orbit right in the middle of the rings creating gaps. The largest of all the moons is Titan. Titan is the second largest moon in the galaxy (it’s bigger than mercury). It has a strong gravitational force and alters the orbit of some of Saturn’s other moons. Titan is the only moon in our solar system with an atmosphere. What makes its atmosphere even more interesting is that it is 95% nitrogen – the same as Earth’s early atmosphere. Studying Titan could teach scientists how the Earth formed billions of years ago.