Agenda: May 28th, 20131) Presentation groups get ready and leave toclassrooms2) Warm-up – 5 min3) Introduction to Galaxies – 10 min4) Categorizing Galaxies Activity – 25 min5) Present Findings – 15 min6) Project Work time – 45 min7) Exit Slip – 5 min
Warm-upPlease answer the following questions on yourworksheet1) What is a galaxy?2) What do you know about galaxies?3) What do you know about different types ofgalaxies?
Introduction to the GalaxyWhat is a galaxy?A galaxy is a cluster of billions of stars, dust, andgas all held together by gravity. Galaxies arescattered throughout the Universe. They varygreatly in size and shape. Not all galaxies lookalike.
This is a galaxyThis is a galaxyThis is also a galaxyDid you notice how the galaxies dont look alike?
When telescopes led to the discovery of galaxies,astronomers observed many differences. In 1926,an astronomer named Edwin Hubble decided toclassify the galaxiesHe could have classified the galaxies by color, orsize, but he decided to classify them according toshape
This is also a galaxyDid you notice how the galaxies dont look alike?There are 3 main types of galaxies, starting withthe elliptical galaxies. Hubble used the letter “E” tolabel elliptical galaxies.Lets take a closer look at this type
When telescopes led to the discovery of galaxies,astronomers observed many differences. In 1926,an astronomer named Edwin Hubble decided toclassify the galaxiesHe could have classified the galaxies by color, orsize, but he decided to classify them according toshapeMost galaxies are elliptical. Some ellipticalgalaxies are circular, while others are extremelystretched out. To deal with this variation, Hubbledivided the "E" classification into 8 sub-groups:"E0", "E1", "E2", "E3", "E4", "E5", "E6", and "E7".E0 galaxies are nearly circular in shape. While E7galaxies are extremelystretched out
Spiral galaxiesHubble called the second type of galaxy you sawa spiral galaxy. It reminded him of whirlpool. Heused the letter "S" to stand for spiral galaxies.A difference between elliptical and spiral galaxiesis that spiral galaxies have a bright center, whichhe called “nuclei”.He classified galaxies with spiral arms into foursub-groups that described how tightly the armswere wound around the nucleus. Lets take a look
S0(S-zero). Bright nuclei,no armsSa: tightly wound armsSb: arms less tightly woundSc: very loose arms
The third type of galaxy reminded Hubble of aspiral with a solid bar across the center. He calledit a barred spiral galaxy. He used the letters "SB"to stand for barred spirals.Bar spiral galaxies
In some spiral galaxies, the arms spiral out, notfrom the center, but from a straight bar of stars,gas, and dust that extends from both sides of thebright nucleus. Hubble classified these barredspirals into sub-groups "a" to "c" in order ofincreasing openness of the armsSBa SBb SBc
Some galaxies dont fit either of these threeshapes, and are called irregular galaxies
Edwin Hubble arranged the main types ofgalaxies and the sub-types into a chart that hascome to be called "The Tuning Fork Diagram".
Think you got it? You will now show what youvelearned by categorizing different galaxies into the3 main types! Mr. Lee will give you your ziplocbag and instructions.
Project work timeWe will spend the rest of the period working onour science projects.Please note that we will use the same classroomrules: 1 warning for classroom noise, and after,the individual or class will work in our textbooks.
Please noteAll non-presentation groups will be presenting inour class on Friday. Your presentations only needto be 1-3 minutes long.Bernadettes group will present in Mr. Nemiroffsclass from 8:20-8:40am
Please noteAll non-presentation groups will be presenting inour class on Friday. Your presentations only needto be 1-3 minutes long.Sammys group will present in Ms. Millers classFriday from 10:35-10:55am