Telescope Use: Measuring an Object’s Size
Please look up at the Moon without your telescope. How big is the Moon in the sky? It is hard to measure the Moon’s apparent size with our naked eyes. Luckily, we have our magical telescopes to help us.
While the telescopes that we are using in class are basic models, they have quite a few useful features. For example, you can use the telescope to measure the size of an object in the sky. Since the Moon is visible today, let’s measure the size of the Moon. First, point the telescope at the Moon and zoom in. Remember, the zoom controls are on the left side of the telescope - the large knob is for large adjustments, and the small knob is for smaller adjustments.
Then, locate the button, which is labeled “S” for “size”. You can find it on the right side of the telescope. Then, push down the button. A ruler will appear in your view - estimate the size of the Moon based on the markings of the lens.
Let’s point our telescopes at the Moon and take a look.
One great thing about this ruler is that it it will zoom in and out as you zoom in and out of the Moon. Remember that the ruler that appears in your lens always measures the size of the Moon as if it were to be seen with a naked eye. For the best results, zoom in as close as you can. As you zoom in, the magical ruler that appears in the lens will show more detailed size increments. You can also see your current magnification level displayed on the upper right side.
Zoom in and out slightly on the Moon and see what happens. Good job, everyone!
Notice how much easier it is to use our magical telescopes than our naked eyes? More complex models of telescopes contain additional magical functions. For example, higher-end models will let you measure the size and other attributes of extraterrestrial objects by saying aloud the quality that you wish to measure. The words will trigger the appropriate charm in the telescope to show the appropriate scales on the screen.
Let’s now discuss how to use your telescopes to measure an object’s albedo.
Telescope: Measuring an Object’s Albedo
Measuring an object’s albedo is rather similar to measuring an object’s size. As I mentioned in a previous lesson, magical albedo is a measure of how much magic is reflected off the surface of an astronomical body - the lowest value possible is “0”, which refers to complete absorption of magic by the surface, and the highest possible value is “1”, which refers to a complete reflection of magic right back at us.
All you have to do is push down on the button with the “A” marking. When you do, the object that you are looking at will turn different shades of green depending on the albedo. In addition, a bar with 10 different shades of green will appear on the side. The shades of green are arranged from light to dark, with the darker shade standing for lower values and the lighter shade standing for higher values. For example, the darkest shade stands for readings of 0.0 to 0.1, the next darkest stands for 0.1 to 0.2, and so on.
Let’s take a look at the Moon. Notice that the bright parts of the Moon have high albedo, while the dark parts of the Moon have low albedo. Also, notice how much of the magic that gets reflected back at the Earth comes from locations with high values. I am going around and checking on everyone in class - if you have a question, please let me know.
Now, we will be going over our assignment for next week.
Viewing the Planets
One challenge when teaching Astronomy is that the objects that we will be looking at may not be visible to us during our class period on Wednesday night. It turns out that the second half of November, for example, is great for viewing only a few planets. Three of them - Venus, Mars, and Jupiter - are visible right before dawn. Sometime before this class and next class, I would like you to go out and view these planets.
I have given everyone temporary passes for permission to be out in the castle around dawn. Please bundle up as the temperatures around that time may be chilly for some, and feel free to bring a classmate or several to the viewing party. I will post this chart here in front of my office and by the southeast corner of the Tower so that you can be reminded of where to look.
Finding the planets is very easy. First, locate the constellation Corvus - it should be in the southeast portion of the sky. Then find the star Spica, which should be left of the top two stars in the Corvus constellation. We will learn more about Spica in future years. The three planets should be aligned on the diagonal, with Venus being the lower planet, Mars being the middle planet, and Jupiter being the planet in the upper part of your view.
I will be in the Astronomy tower on Wednesday and Friday morning at dawn. If you have trouble finding these planets, please come seek me out, and I will help you. Bring your friends and housemates if you would like. This is important, as next lesson we will be learning a little more about these planets and their moons.
Beyond the Earth and the Moon
So far this year, we’ve focused mostly on the magical relationships between the Earth and the Moon. While the Moon is very important to magic on Earth, there are also many other Astronomical bodies present in our Solar System. There is, of course, our Sun - the producer of all magic in the Solar System. Practically all magic that is reflected off Solar System planets has originated from the Sun. Also, the Sun pulls all of the Solar System planets, as well as objects such as asteroid belts and some comets, into orbits, which allow us to utilize the magical relationships we use today. In fact, the term “Solar System” includes the Sun and everything that revolves around it, from the great planets to the smallest rocks in the Asteroid Belt.
As for the planets in the Solar System, there are eight that are considered in the Magical world (and most of the Muggle world) to be planets. From closest to furthest from the sun, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The four that are closest to the Sun are considered the Inner Planets, and they share similar features. Likewise, the last four are considered the Outer Planets, and they also share commonalities. There is also the dwarf planet Pluto. When the International Astronomical Union (IAU), one of the premier Muggle Astronomical associations, deemed that Pluto is not a planet in 2006, there was controversy, and there are some today who still consider Pluto to be a planet. Either way, Pluto is a part of the Solar System and thus has some effect on astronomical magic.
In addition to the many planets of the Solar System, there are also many moons. The Earth is unique in the Solar System in that it has exactly one moon, and our Moon is also relatively large compared to the Earth. In fact, the Earth’s Moon is so large that it is able to totally eclipse the Sun during a solar eclipse. Among the Inner Planets, there are only three moons - Earth’s Moon, and Mars’ potato-shaped moons, Phobos and Deimos. In contrast, many of the Outer Planets have a whole collection of moons, and new moons are still being discovered. For example, Jupiter currently has the most known moons at the time of this lesson. Of Jupiter’s 67 known moons, four of the most famous - the Galilean moons - were used by Galileo Galilei as evidence for a Sun-centered Solar System. Even Pluto, perhaps the most famous planetoid in the Solar System, has five moons. While moons have similar features, they also have unique properties. For example, Europa, perhaps the most well-known of the Galilean moons in the wizarding world, is covered in ice.
Furthermore, there are other features of the Solar System worth noting - asteroids belts, comets and the like. Then there is magic coming from outside of the Solar System - in particular, constellations for astrology. The whole universe contains objects that impact and emit magical energy, which makes Astronomy such an important and vital subject.
Inner Planets vs. Outer Planets
The eight planets in the Solar System are, as mentioned above, split into the Inner Planets and the Outer Planets. The Inner Planets refer to Mercury, Venus, Earth, and Mars, while the Outer Planets refer to Jupiter, Saturn, Uranus, and Neptune. The image I have presented above shows the eight planets in the Solar System scaled according to size, with the Inner Planets in the front and the Outer Planets in the back.
Perhaps the most obvious difference between the Inner Planets and the Outer Planets is this size difference - the Outer Planets are much larger than the Inner Planets. In fact, Earth is the largest of the Inner Planets even though it is quite small for a planet. That being said, the planets of Mercury, Venus, and Mars have much more of a magical effect on Earth than, say, Uranus or Neptune. This is because Mercury, Venus, and Mars have larger observed sizes since they are closer to the Earth, and thus the Inner Planets also have higher A.M.E.’s than Uranus or Neptune. Of all the Outer Planets, only Jupiter and Saturn were noticed by Astronomers before telescopes, and thus - due to their observed size and brightness - these planets have relatively noticeable A.M.E.’s and thus have a strong magical effect on the Earth.
Two other differences between the Inner Planets and Outer Planets are surface and composition. The surfaces of the Inner Planets are rocky, and although planets such as Venus and Earth - the two largest of the Inner Planets - have thick atmospheres, any spacecraft that attempted to land on the planets would be able to land on solid ground. Thus, all four of the Inner Planets have surface features. You will find landscapes of volcanic origin as well as craters. If you go deeper into these planets, you will also find that these planets are made of many heavier elements such as metals, and the cores are very metallic.
In contrast, the Outer Planets, while they are large, do not have hard surfaces. They are called “Gas Giants” because they are made of gas: a spacecraft that attempts to land on such a planet would not find a solid surface. Composition-wise, the Outer Planets are made of hydrogen and helium, the same components that make up our Sun. The Outer Planets also have ring systems and tend to have interesting moons.
