IN OUR LAST POST, I gave you guys a brief introduction to naked eye astronomy by showing you a bit about how the heavens move every night. Now, I'm going to have you guys actually apply what you've learned, and go out into the night and try and find a few basic constellations and stars! We will start with one of the most famous: the Big Dipper!* But first, pull up the video supplement by clicking HERE, or clicking it below. We will be consulting it several times throughout this post, so make sure that you have this pulled up!
The Big Dipper is officially an asterism within the official constellation of Ursa Major, or the "Big Bear." In this case, an asterism is when a portion of a constellation is more famous than the official constellation. We will talk about another important asterism, Orion's Belt, in just a few minutes! In the meantime, below is a picture of the constellation Ursa Major. The Big Dipper appears to be seven very bright stars that make up the tail of the bear. Besides being an obvious and easily recognizable constellation, the Big Dipper is important for another reason: two of its stars point the way to Polaris, or the North Star! We talked about Polaris in the last post, so to refresh yourself on the importance of this star, make sure to check out the link I provided above.
At this point, consult Part I of the video supplement, a link to which I have provided at the top of this post. Part I shows you not only where to look for the Big Dipper in the night sky, but also outlines the constellation, and shows how to use the stars Merak and Dubhe as "Pointer Stars," as guides to locate the North Star. Below you can see a picture of the same thing. The constellation of the Big Dipper is outlined in red, with the yellow line being drawn from Merak and Dubhe to Polaris, which has a blue circle around it.
At this time of year, the Big Dipper rests on the horizon at sunset, and not all of it is visible. It isn't until around 21:00 (9:00 PM) that the entire constellation completely clears the horizon, and doesn't get high in the sky until after midnight. As we get closer to summer, watch for the position of the Big Dipper at sunset: it will continue to rise high in the sky, and in several months will be at the same position at sunset as it is at midnight tonight. Furthermore, for the most part, the Big Dipper does not drop below the horizon here in Boulder. This is because for this latitude, the Big Dipper is a circumpolar constellation, meaning it never sets. (To learn a little more about what it means to be circumpolar, make sure to check out the last post.)
Next, we will use another constellation to locate two more objects of interest in the night sky. The constellation is the very famous constellation of Orion. These days, Orion has already risen in the east by sunset, and is instantly recognizable. Even in the brightness of many cities, the most prominent stars are still visible. Below is a picture of Orion, with art of the constellation depiction overlaying the stars.
Now we refer to Part II of the video supplement. Part II shows us where to see Orion, and also shows us how to use the asterism of Orion's Belt to locate two objects of celestial significance: the bright star Sirius, and the star cluster called the Pleiades. Just as with the Big Dipper and Polaris, the constellation itself is outlined in red, and the yellow line points the way to Sirius and the Pleiades, which are both circled in blue.
Sirius will not have risen immediately after sunset at this time of year, and you will have to wait for 20:00 or 21:00 to get a nice view of it. Despite the fact that, at a mere 8.6 light-years, it is only the 5th closest star to the Earth (not including the Sun), it is the brightest star in the night sky when viewed from Earth. Sirius is a part of the constellation Canis Major, which we will discuss in a future lesson.
You can see Orion in the center of the photograph. The bright star in the bottom of the photograph a bit to the left is Sirius.
Most constellations are composed of stars that have little to no physical relation to each other. To see what I mean, refer to Part III of the video supplement. In Part III, we take a virtual voyage to Alnilam, the center star in the belt of Orion. As you can see as we get closer and the constellation becomes more and more warped, it is only on Earth and in the nearby Solar System that these stars appear to have any relation to each other. There are notable exceptions, however, and when it comes to these exceptions, the Pleiades shine brighter than all the rest. This is where we travel to in Part IV of the video supplement, to Alcyone, the brightest star in the Pleiades.
Another picture of Orion that I took in my backyard. Alnilam is the center star in the Belt.
Called "Subaru" by the Japanese (yes, just like the car company), the Pleiades is actually an open star cluster, composed of many more stars than can be easily viewed here on Earth, possibly as many as 500! Located in the classical constellation of Taurus the Bull, almost every culture that could see the Pleiades created some sort of story about them. Although the stars that are visible within it are not very bright compared to the main stars of Orion or the Big Dipper, it is their close proximity to one another that make the Pleiades instantly recognizable. You might even be able to see them in the city, but you will have to know where to look, which is covered in Part II of the video supplement.
The Pleiades are the cluster of stars in the center of the photograph.
Next time, we will look at some more of the major constellations in the vicinity of Orion, including the aforementioned Canis Major and Taurus, as well as Auriga and Gemini. We will also learn a bit about the current location of Jupiter, and the possibility of viewing some of Jupiter's moons!
**I am writing from a latitude of about 40 degrees North, in Boulder, Colorado. The information in this post can apply to anyone within that belt around the world. For example, people in Beijing and Baltimore, both cities around 40 degree North latitude, will see the same thing every night as people in Bursa and Boulder.
Works Cited:
The video and some of the pictures in this post were made using the Stellarium app or the Celestia app.
At the beginning of the semester, just a few months ago, I paid very little attention to the night sky. That all changed when I took the awesome Ancient Astronomies course at CU with professor John Stocke. Although I'm definitely not an expert, I've learned a lot, and I love sharing it with you guys. However, sometimes it can be tough to tell what exactly you are looking at, where you should look for something, or even how the sky changes throughout the day or year. Hopefully this post, as well as any others I make, can help you figure things out.*
To further assist you in your understanding, I made a video supplement to this post. Below is the video embedded within the post, but if for whatever reason that is not working, click HERE to check it out. I refer to it several times later on in the post, and it just makes things easier to understand. You can watch it as you read along.
First off, look at the picture below. In it, we see the Earth encased in a plastic globe with the constellations printed on it. For our purposes, that plastic globe with the constellations printed on it is called the celestial sphere. Inside the celestial sphere, you can see a tiny little yellow ball: the Sun. (I can't actually see it in this picture, but the Moon is probably inside the ball as well.) Is that how the universe looks then? Of course not. We've known for many, many years that the sun is neither that close in size or distance to the Earth. However, this model is how we can think of the night sky, especially when it comes to naked eye astronomy. It shows, from where you are on the Earth's surface, what constellations the Sun and the Moon are in, and what constellations you can see from your specific point on the planet.
A lot of the time in naked eye astronomy, we say things that mean one thing while they sound like another. Like what I just said: "what constellations the Sun and the Moon are in." If we were to look up at the night sky and see the Moon smack-dab in the middle of a constellation, we realize that the distance between the moon and the stars is actually much greater than what it initially appears. However, for our intents and purposes and to make things simpler, we just say "the Moon is in the constellation of...." Just like when we talk about the daily motion of the Sun. When we say that the Sun sets or rises, we realize that the Earth is the celestial body that is moving. But from an Earth-bound perspective, it doesn't look that way.
Before we go any further, it's time to meet a very important star: Polaris, the North Star. As you probably know, Polaris is called the North Star because it is situated directly to the north. This star sits almost exactly on something that is called the North Celestial Pole. Look back up at that globe for a second. See that metal bar that sticks right through the middle of the Earth? That's the Earth's axis of rotation, or how the Earth spins around. And see how that pole intersects with the celestial sphere? Those are the North and South Celestial Poles.
Confused? I thought you might be. I know I definitely was. Stand up, find someplace where you can safely spin around, and start to spin, looking straight out in front of you. After doing that a few times, look straight up. Notice how when you looked straight in front of you, everything seemed to move, and move pretty fast too. Now, when you look up at the ceiling, you can still see everything moving, but there is a single point that doesn't move at its center. That single point is the equivalent of the North Celestial Pole.
Now, let's look at the video that I made to accompany this post. We will start with "Part I: Polaris in Boulder". Part 1 shows how the celestial sphere spins around Polaris over the course of a single night. This part of the video takes place at 40° N, and is facing north. "Part II: The Equator" shows the spinning celestial sphere from the point of view of someone standing slightly north of the Equator, just far enough that they can still see Polaris. They are still facing north. "Part III: The North Pole" tracks the daily motion of the celestial sphere from the perspective of someone who is lying on their back and looking straight up, situated at the North Pole. Try and draw comparisons between what you see at the Equator and the North Pole; and what you saw while you were spinning and looking straight in front of you, and straight up. While you watch all three clips, notice how in each one there are some stars and constellations that never set, with the fewest being at the Equator and the most being at the North Pole. These stars and constellations are called "circumpolar."
So now it's time to introduce two different types of celestial motion: daily, and annual. Daily motion can really apply to anything in the night sky, and is what we've just been looking at. The three parts of the video taking place in Boulder, the Equator, and the North Pole were three views of daily motion at different locations on the planet. Even with the video to help guide you, it can be difficult to absorb, so this might be a good place to stop and absorb what you have learned.
Excellent. Now, on to the other main type of motion that we will discuss today: annual motion! Annual motion applies to the celestial objects that move over shorts amount of time (i.e. not thousands or millions of years) against the backdrop of the celestial sphere: the planets, including the Sun and the Moon. The motion of the moon amongst the heavens is arguably the most easily observed, as it changes constantly, and you can compare its relative position with that of the sun. A discussion of the moon and its phases will take up an entire post though, so we can do that later. For now, it's just important to recognize that the main objects that we see moving through the sky from night to night are the planets.
There are two such planets easily observable in the night sky right now, and I fear that as I am writing this it might already be too late for one. Venus and Jupiter are typically the brightest planets in the sky, with the former being quite variable in its brightest and degree of visibility throughout its journey around the sun. Again, a topic for another time. If it can still be seen in the night sky, however, look for Venus right after the Sun sets in the west.
I think I've used this picture like four times or something now, but it's the best one I've got. The Moon is in a waxing crescent phase above Venus as the Evening Star, the bright object between the Moon and the mountains. We will talk more about Venus and its varied locations in the morning and evening sky some other time. This picture was taken in early November here in Boulder.
So what did you hopefully learn in this post? This post was really just a rudimentary introduction to how the sky moves each night, also called daily motion. You should remember the term "North Celestial Pole," and remember that that is where Polaris is located. You also briefly learned about what it means to be a circumpolar stars or constellation. We just barely touched on annual motion, a topic we will delve into deeper later, as well as the phases of the moon. In the next Intro to Astronomy post, I will show you how to locate several celestial objects and constellations, including The Big Dipper, Polaris, Orion, and Jupiter. Until then, clear skies!
*I am writing from a latitude of about 40 degrees North, in Boulder, Colorado. The information in this post can apply to anyone within that belt around the world. For example, people in Beijing and Baltimore, both cities around 40 degree North latitude, will see the same thing every night as people in Bursa and Boulder.
Works Cited:
All of the videos here were made using footage from the excellent Stellarium app. Check it out, it's free!
Recently for my Ancient Astronomy class, I did a brief paper on Native American legends surrounding the stars Altair and Fomalhaut, which are two of the brightest stars in the southern sky of the United States. It is of no surprise that numerous Native American legends have been created surrounding these two stars, and the stars in their direct vicinity. In the post, I used screenshots from the Stellarium.
One of these constellations is what the Greeks referred to as Aquila or the Eagle. Within Aquila is a line of three stars that is often referred to as the head of the eagle or the head of Aquila, consisting of Altair and the two stars on either side: Alshain and Tarazed. These three stars are in a line that is fairly straight, and has led to many interesting myths.
One myth comes from the Maricopans, a tribe native primarily to southern Arizona. For the Maricopans, the head of Aquila was called “Cold’s Cottonwood,” a constellation that would appear in the sky at dawn in January, “when the yellow blossoms appear on the cottonwoods.” The flowering part of the cotton plant, known as a catkin, does resemble the stars in the head of Aquila.
Another myth is the Coeur d’Alene story of a trio of people running in a race, which is represented by “three stars in a row.” A good candidate for this constellation is the head of Aquila, as Orion’s Belt (a much brighter trio of stars in a row) is thought to have been a bark canoe.
While Altair was an important star for some tribes, for the Klamath of southern Oregon, the star Fomalhaut is more prevalent in their stories. “Kai,” or “Rabbit,” was said to be a star that would appear in the southeastern sky before the sun rose in May and June, and was supposed to be able to “freeze the lake by looking at it.” Fomalhaut, which not only can be seen in the southeast just before dawn in May and June, is also the brightest star in that particular area of the sky, making it a very likely candidate for Kai. Numerous other tribes had stories surrounding Fomalhaut as well, such as the Luiseño, who called Fomalhaut “Nawiwit Chawachwish” and believed that this star was a great chief who “went to the sky” after he died; and the Northern Paiute, whose star “Big Woman,” or “Paba’i-yü-mogo’tni,” also fits the description of Fomalhaut.
Sources:
Miller, Dorcas S. Stars of the First People: Native American Star Myths and Constellations. Westwinds Press, 1997. (accessed December 7, 2013).
