Objectives
Memorize the order and names of the 8 planets
Classify the planets
Analyze the reasons why Pluto is considered to be a planet anymore
Think about the scale of the universe
Introduction
There is literally an entire universe to consider when talking about space, but we must start somewhere. So, why not start with what we experience everyday and what we always hear about: the Solar System. The Solar System is the vast collection of space objects (or in fancier terms, celestial bodies) that orbit the Sun. This, of course, includes the 8 planets, but also smaller objects like comets, asteroids and dwarf planets. In this lesson, we will be doing an overview of the planets and a explanation as to why Pluto is not a planet. Finally, after this basic overview of the Solar System, we will take some time to think about the scale of the universe.
The 8 planets
As you may already know, a planet is a large collection of mass orbiting the Sun. The Solar System has 8 planets which are, in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. These 8 celestial bodies are divided into two groups: terrestrial planets (Mercury, Venus, Earth and Mars) and gas giants (Jupiter, Saturn, Uranus and Neptune). Terrestrial planets are rocky, while gas giants, as their name suggests, are made of gas.
On diagrams, the planets of our solar system appear to be very near each other, but this is a common misconception. The planets are separated by vast distances and, as well, the Solar System is unimaginably huge. In fact, Neptune (the farthest planet from the Sun), is over 4 billion km away from it!
One challenge that some people face is the memorization of the order of the planets. To make it simpler, try making a sentence out of the first letters of each of the planet names. A very popular one is: My Very Energetic Mother Just Served Us Nachos. Try making your own!
Why is Pluto not a planet?
In this lesson, we will talk about why Pluto is not longer considered a planet, but rather a dwarf planet. The reason for this is that some are still confused as to the reasons behind its classification and are curious about it.
After much debate as to whether Pluto should be considered a planet or not, the IAU (International Astronomical Union) adopted Resolution B5, which stated that a planet must:
Orbit the Sun
Have enough gravity to form into a sphere
Clear its orbit of any debris/other celestial bodies
Pluto actually fits into the first two of these criteria: it orbits the Sun and is a sphere. However, Pluto has not cleared its orbit at all. It actually sits in the Kuiper belt, a large collection of small rocks past the orbit of Neptune. In a future lesson, we will learn about the Kuiper Belt.
The scale of the Universe
Our Solar System is most definitely not the only one in the Universe. For starters, our Sun is only one out of billions and billions and billions and billions of other stars in the Milky Way galaxy. On top of that, our galaxy is only one out of an uncountably large amount of galaxies in the Universe. In all, the Solar System, in terms of size, is insignificant.
Conclusion
Aren’t you excited to look deeper into the far reaches of the Universe and also to analyze the functions of things closer to home like, for example, how the moon and earth move in relation to each other?
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