Galaxy What is a galaxy It is a

Galaxy �What is a galaxy? �It is a collection of billions/millions of stars, planets, dust and gas held together by gravity.

Do Now � Turn to a partner and discuss: What are two kinds of optical/visible light telescopes scientists use to gather information from space? How do you think instruments using the electromagnetic spectrum would allow scientists to view space differently than using a refractor or reflector telescope?

NC-185 �Approximately 8. 5 light-years away �Light-year: 6 trillion miles

Galaxies �Goal: I can analyze how galaxies are classified. I can identify characteristics of our Milky Way galaxy. �Lab Group Classification Activity �Discuss classifications and re-group �Tree map notes �Exit Ticket �Galaxy Homework

Lab Activity �The Hubble Space Telescope has just received exciting new images of 30 galaxies. Your job is to work with your team of scientists to classify these galaxies. �Classify the 30 galaxies in your envelope in whatever kind of groups you decide. You must provide reasoning for your classification. Your team must record the categories and evidence for support on your lab sheet.

Galaxies �Work with your team to reclassify your galaxies. �Distinguish between barred spiral and spiral galaxies. �Spiral �Barred Spiral �Elliptical �Irregular

Galaxies �Galaxies are huge groupings of stars, gas, planets, and dust held together by gravity.

Spiral Barred Spiral 2, 5, 8, 10, 9, 27, 30 15, 16, 18, 19, 21, 25, 28, 7, 14, 20 ES: 7, 14, 20 Elliptical Irregular 3, 6, 13, 23, 1, 4, 11, 12, 26 17, 22, 24, 29

GALAXIES

Galaxies �Galaxies are huge groupings of stars, gas and dust held together by gravity. �Galaxies differ greatly in size. Some contain a hundred million stars to the largest containing more than a trillion stars! �Scientists classify galaxies.

Galaxies �Scientists classify into 3 categories by shape �Spiral �Elliptical �Irregular

Galaxies �Spiral galaxies have arms of stars, gas and dust that curve away from the center in a spiral or pinwheel pattern. �Spiral galaxies are disk-shaped, have a bulge in the center. �Most of the stars in the disk & bulge are older stars. However, the spiral arms within the disk contain many young, bright stars.

Galaxies �In addition to the spiral galaxy, there is a barred spiral. This type of galaxy is similar in make-up to a spiral galaxy but seems to have its arms connected or linked by a bar.

Galaxies �Elliptical galaxies are shaped like spheres to football or egg-shaped. Unlike spiral galaxies, elliptical galaxies have almost no dust or gas between stars and all of their stars are old.

Galaxies �Irregular galaxies are galaxies without a definite shape. They are generally smaller than the other type of galaxies and contain fewer stars.

Spiral *Pinwheel Shape Barred Spiral *Similar to Spiral galaxy *Arms of stars, *Arms gas, and dust connected by that curve away bar in center from center Has bulge in center and diskshaped Most stars in disk are old Spiral arms have more young stars Young and old stars are present Elliptical Irregular *Shaped like *No definite spheres or eggs shape *Mostly old stars present Almost no dust or gas *Smaller than other galaxies with fewer stars Young and old stars are present Contains gas and dust

Galaxies �The Earth lies within the Milky Way Galaxy. �The Milky Way is a spiral galaxy and is 100, 000 light years across. �The bulge of densely packed stars at the center is approximately 26, 000 light years away from the sun. �The stars in the Milky Way orbit the galaxy’s center at very high speeds, still it takes our solar system about 250 million years to complete one orbit. The age of the Milky Way has been calculated to be about 13 billion years old.

Galaxies �It’s all about perspective

Galaxies – Black Hole center of Milky Way

Galaxies �Most large galaxies seem to have super massive black holes at their centers. At the center of the Milky Way is theorized to be a black hole with the mass of about 3 million times that of the sun. �A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.

Galaxies �The center of some galaxies look very bright. This brightness is attributed to quasars. � Quasar stands for quasi-stellar which means “seeming like a star. ” Quasars eject hot gas from their centers giving off a very bright light.

Exit Ticket Name _____________ 1. What kind of galaxy is shown in image #1? ________ 2. What kind of galaxy is shown in image #2? ________ 3. What kind of galaxy is shown in image #3? ________ 4. What kind of galaxy is shown in image #4? ________ 5. What is the name of our galaxy? And what shape is it? (add) ____________ 1 2 3 4

Exit Ticket What kind of galaxy is shown in image #1? 2. What kind of galaxy is shown in image #2? 3. What kind of galaxy is shown in image #3? 4. What kind of galaxy is shown in image #4? 5. What is the name of our galaxy and what shape is it? 6. Bonus: Name one characteristic of each of the galaxies in #1 -4. 1 2 3 4

Galaxies �Goal: I can analyze how galaxies are classified. I can identify characteristics of our Milky Way galaxy