Sky Science

6.7.2 Describe the location and movement of individual stars and groups of stars (constellations) as they move through the night sky.

Constellations Stars in My Backyard: Star Charts Video

What is a constellation? A constellation is a pattern of stars.

What is a constellation? Constellations are bright stars grouped according to patterns they make in the sky (such as Orion or Ursa major). There are 88 constellations or star clusters that cover the sky that are recognized by the International Astronomical Union (IAU). Many of their names come from characters in ancient mythology and were mapped out by Greeks thousands of years ago.

Constellations On a dark, clear night, a first glance at the sky might reveal hundreds of stars. Look a little closer and it might seem as though some stars appear to form patterns. You can see these patterns night after night, year after year. People around the world have been studying and naming star patterns for hundreds of years.

What is a star? A star is a gaseous body that produces its own energy. Stars release energy as light and heat.

Sun Light And Star Light The Sun is a star and is considered an average sized star. It is also the closest star to earth. All other stars are seen as tiny points of light in the sky.

Star Brightness The brightest stars in a constellation are considered 1st magnitude stars. After the 1st magnitude star, they are grades 2nd, 3rd, 4th, and 5th according to the brightness.

Asterisms There are many unofficial star groups called asterisms. The stars in an asterism, like a constellation, form a recognizable pattern in the sky. An asterism could be a small part of a larger constellation, or it could contain stars from more than one constellation.

Examples of Asterisms One of the most well-known groups of stars, the Big Dipper, is an asterism. It is part of a much larger constellation called Ursa Major, or the Great Bear. Another familiar asterism is the Summer Triangle. It is made up of three bright stars from three constellations – Cygnus the Swan, Aquila the Eagle and Lyra the Harp.

Ursa Major Includes the Big Dipper

Constellations and Asterisms Constellations and asterisms are useful markers in the sky. When people are new to viewing the night sky, they often look for these familiar groups of stars to help them find other stars and objects.

Star Patterns It is important to remember that the stars in a constellation often do not have any relationship to each other in outer space. Most of the stars in a constellation are light years away from each other. If you viewed the same stars from a different part of the galaxy, you would probably not see the same star patterns.

Movement Across the Sky If you spend any amount of time watching the stars, you will see that all the stars appear to move across the night sky except for one. This star is Polaris.

Polaris Polaris can be found in the northern part of the sky. Because it does not move, Polaris has been used for navigation. If you are facing Polaris, which is sometimes called the North Star, you are facing north.

Polaris Polaris or known as the North Star is not the brightest star, it is only 2nd magnitude. It is the only star in the sky that does not seen to move. Polaris is always north.

Continued The two stars in the bowl of the Big Dipper (pointer stars) always point to Polaris. The Big Dipper is a group of 7 stars. It is part of the constellation Great Bear.

Circumpolar Constellations Constellations that can be seen year-round are called circumpolar constellations. Each night, the circumpolar constellations circle around a single point. They are always visible. The point they circle around is Polaris.

Main Circumpolar Constellations The main circumpolar constellations include: The Great Bear (Ursa Major) The Little Bear (Ursa Minor) Cassiopeia Other constellations that appear to move around Polaris: Draco the Dragon Cepheus

Why do the stars appear to move? Circumpolar constellations appear to move over the course of an evening. This is because Earth is rotating underneath your feet!

Rotation of Big Dipper The movement of objects in the sky are regular and predictable. This is due to the rotation of the earth on its axis.

Cassiopeia throughout the night If you were able to observe the position of Cassiopeia over the course of 24 hours, the drawings you would make would most likely look like these.

Positions of Circumpolar Constellations The positions of circumpolar constellations change as the seasons change. You can see these changes in the Big Dipper and how it appears with Polaris.

Cassiopeia over the year If you were able to observe the positions of the Big Dipper and Polaris at midnight over the course of one year, the drawings you would make would look like these.

Polaris Stays Put Notice that Polaris does not change position. All the other stars appear to move around it. This is because Polaris is the only star in the Northern Hemisphere that has the axis of Earth pointing directly at it.

Constellation Scavenger Hunt Working independently or with a partner, find out some information about different constellations! You can use online resources, books, or provided handouts. Good luck!

Finished Early? Go to our class website, stleograde6.weebly.com and click on the constellations (Ursa Major) picture under the Science tab. Try and locate each of the constellations in the different seasons!

Orion The Orion Nebula is the nearest star formation region to the Earth and consequently particularly well studied.

Big Dog A small and compact constellation of the southern hemisphere. The brightest of all stars, Sirius, belongs to this constellation.

Charioteer Auriga is an ancient Northern Hemisphere constellation featuring one of the brightest stars in the heavens. The youth Auriga wields a whip in one hand and holds a goat (Capella) and her two kids in the other.

Bull Taurus is traditionally depicted as the forepart of a bull, in reference to the Greek legend in which Zeus either assumed the form of a bull himself or sent the bull to carry Europa over the sea to Crete.

Eagle It is sometimes depicted as an eagle. It contains the bright star Aquila

Lyre Although many civilizations represented it as a bird, it was also depicted as a tortoise.

Twins Gemini is traditionally depicted as two men. The two brightest stars in Gemini. Are two of the brightest stars in the sky and were identified by the Greeks with two children, in most accounts the twin sons of Zeus and Leda.

Swan It was depicted as a bird by most ancient cultures. It is sometimes called the Northern Cross because five of its brightest stars form a huge Latin cross.

Lion The Egyptians, Babylonians, Arabs, and Greeks all represented this constellation as a lion; it may be the first constellation to be pictorially represented.