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: Jupiter, The Big Boy

Bring on the gas giants! And what better one to start with than the biggest planet in our solar system, Jupiter.


Jupiter is a big boy. In fact, it is so big that it Jupiter and its moons are basically a mini solar system within our own. When I say big, I mean big (compared to the other planets). It would take over 1,000 Earths to make something the size of Jupiter. Being so big makes it easy to see from Earth with the naked eye. Jupiter will be the second brightest planet in the sky (second to Venus). Because of its size, the ancient Romans named this planet after the king of their gods, Jupiter (the Greeks called it Zeus).

There is very little (if any) solid material on Jupiter – it is a giant ball of gas and liquid. It is comprised mostly of hydrogen and helium (more similar to the sun than the Earth), but there may be a very small solid metal core. If Jupiter was 80 times larger, it actually would have become a star and not a planet. Being so large also means it is the most massive (heaviest) planet, but since this weight is primarily Hydrogen and Helium (the two lightest elements), it is not very dense.

It takes this ball of gas 4,333 Earth days (about 12 years) to orbit around the sun. Jupiter can make one full rotation on its axis in 9 hours 56 minutes. That is faster than any other planet. Spinning so fast makes the center of Jupiter bulge out such that the diameter of the planet 7% larger at the equator than at the poles.

The average temperature of Jupiter (taken at the level we would consider ground level and also where any life would be, if there is any) is 70°F (21°C) – that is room temperature on Earth. Other than pleasant temperatures, the weather forecast on Jupiter calls for clouds and wind. The clouds are made of different chemicals that provide Jupiter with its fun colors. The high clouds of frozen ammonia are white and the darker blue clouds are found below them. The Great Red Spot is this planets most distinguishable beauty mark. It is a swirling spot of gas that is big enough for three Earths to fit inside of it. It really doesn’t move much and can shift colors from opaque to deep red (the color comes from small amounts of sulfur and phosphorous mixed with the ammonia crystals).

No giant planet wants to travel alone and Jupiter is no exception. This planetary rockstar has picked up a bunch of moons – 62 to be exact. The largest four, the Galilean moons (they were discovered by Galileo) are Io, Europa, Ganymede and Callisto. Jupiter is so big that it even has enough gravity to hold a comet in orbit.

A little known fact to most people is that Jupiter also has rings. That’s right, take that Saturn, you’re not the only one! Discovered in a picture taken by Voyager 1, the rings of Jupiter encircle the planet right around the equator. Jupiter has 3 faint rings that are made of tiny partials (similar to the size of particles in cigarette smoke). The main ring is around 20 miles (30 kilometers) thick and has an outer edge approximately 80,000 miles (129,000 kilometers) from the center of the planet.

Robert’s Out of This World Space Odyssey: The Asteroid Belt, Where They Teach You to Hate Dinosaurs

It’s time to say goodbye to the “Earth-like” rocky planets of the inner galaxy and move on to explore the gas giants. If you really were traveling from Mars to Jupiter, you would run into another major component of our galaxy: the asteroid belt.

The asteroid belt (the main belt) is an area of the solar system between the orbits of Mars and Jupiter that contains over 4,000 named asteroids that are just orbiting the sun (there are millions of asteroids total). The vast majority of the asteroids in our solar system can be found in the belt. That’s great and all, but if you don’t know what an asteroid is, then you probably do not care.

An asteroid is basically leftover material from the formation of our solar system about 4.6 billion years ago. Sometimes referred to as minor planets, asteroids are nothing more than pieces of space rock. These rocks are leftover because when Jupiter finished forming, it had such an affect that the material between it and Mars stopped forming as well, leaving us with the asteroid belt.

Asteroids are irregularly shaped and covered in collision marks. They all orbit the sun and even rotate – although it looks more like they are just tumbling along. They vary greatly in size. Ceres is the largest and is roughly 952 kilometers (592 miles) in diameter. This monster asteroid is said to contain 1/3 of the total mass of all asteroids. Others are not even a mile in diameter. The smallest asteroid ever discovered is barely 20 feet across. Some of the larger asteroids have small moons orbiting them. Several pair off (sometimes in groups of three) and orbit each other as they orbit the sun.

Getting through the asteroid belt isn’t a big deal. It is such a large space and the asteroids are typically rather small (in comparison to other things in space). If you took every asteroid in our solar system and put them together, you wouldn’t even be able to make something the size of our moon.

The asteroids within the belt are all unique and are classified into three main categories based on their composition. S-Types (stony) are made up of iron, nickel and silicates, M-Types (metallic) are made of metallic metals (i.e. nickel and iron) and C-Types are made of silicates and clay (these are the most common).

Jupiter is a big boy and has a ginormous gravitational field. As it orbits it is able to alter the belt and send some asteroids flying out of the belt in random directions throughout the galaxy. When an asteroid is sent our direction it is referred to as a near-Earth asteroid. Scientists are always tracking these crazy rocks. A near-Earth asteroid that collided with the Earth is believed to be what killed the dinosaurs.