Galaxies and Star Galaxies and Star ClustersClusters

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What is a Galaxy?What is a Galaxy?A huge collection of gas, dust and A huge collection of gas, dust and

hundreds of billions of stars and hundreds of billions of stars and planets. These stars are attracted planets. These stars are attracted to each other by the force of gravity to each other by the force of gravity and are constantly in motion. and are constantly in motion.

We are in the Milky Way Galaxy. The We are in the Milky Way Galaxy. The night sky looks like milk splashed night sky looks like milk splashed across it.across it.

We are in the arm of our Spiral Galaxy.We are in the arm of our Spiral Galaxy.

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Astronomers estimate that there Astronomers estimate that there are at least 400 billion stars in our are at least 400 billion stars in our Milky Way Galaxy.Milky Way Galaxy.

Galaxies come in various shapes: Galaxies come in various shapes: spiral, (like the Milky Way), barred spiral, (like the Milky Way), barred spiral, elliptical, irregularspiral, elliptical, irregular

Spiral, barred spiral, elliptical, Spiral, barred spiral, elliptical, irregular irregular (p. 439)(p. 439)

The Milky Way ActivityThe Milky Way Activity

Open books to page 461, Figure 2:Open books to page 461, Figure 2: Draw and label the top and side views Draw and label the top and side views

by dotting with pen or pencil.by dotting with pen or pencil. On the back side create by dotting) On the back side create by dotting)

and label the 4 types of galaxies. (p. and label the 4 types of galaxies. (p. 462 top paragraph)462 top paragraph)

We know which way the stars are moving We know which way the stars are moving by the way the arms are arranged.by the way the arms are arranged.

QuasarQuasar

What is a What is a QuasarQuasar??

Objects that look like faint stars Objects that look like faint stars but emit up to 100x more energy but emit up to 100x more energy than our entire galaxy.than our entire galaxy.

What is a light-year?What is a light-year?

The distance that light rays travel The distance that light rays travel in one year. (9.46 x 10in one year. (9.46 x 101212 km) km)

Star ClustersStar Clusters

What is a What is a star clustersstar clusters??

Groups of stars that are fairly Groups of stars that are fairly close and travel together. close and travel together.

These clusters may have as few as These clusters may have as few as 10 stars or as many as a million - 10 stars or as many as a million - too small to be called a galaxy.too small to be called a galaxy.

Ex. galaxy – city, star cluster - suburbEx. galaxy – city, star cluster - suburb

Questions 2, 3: P. 463Questions 2, 3: P. 4632. Arrange the following in order of size, 2. Arrange the following in order of size,

starting with the largest: star cluster; starting with the largest: star cluster; galaxy; universe; star; planet.galaxy; universe; star; planet.

The largest object is the universe, followed by The largest object is the universe, followed by galaxy, star cluster, star, and planet.galaxy, star cluster, star, and planet.

3. A certain star is located 60 light-years 3. A certain star is located 60 light-years away from us. Which galaxy do you away from us. Which galaxy do you think this star is in?think this star is in?

The star must be located in our Milky Way The star must be located in our Milky Way Galaxy because our galaxy is huge, about Galaxy because our galaxy is huge, about 100,000 light-years across.100,000 light-years across.