Notes 10 - Galaxies Mrs. Gordon Saturday, October 03, 2015Saturday, October 03, 2015Saturday, October 03, 2015Saturday, October 03, 2015.

Notes 10 - GalaxiesNotes 10 - Galaxies

Mrs. GordonMrs. Gordon

Wednesday, April 19, 2023Wednesday, April 19, 2023

1. What is a Galaxy?1. What is a Galaxy?

A. A. GalaxyGalaxy - a massive, gravitationally bound system - a massive, gravitationally bound system consisting of stars, interstellar medium, and dark consisting of stars, interstellar medium, and dark matter.matter.

B. > 100 billion galaxies in the observable Universe – B. > 100 billion galaxies in the observable Universe – each containing 100’s of billions of stars.each containing 100’s of billions of stars.

Image Source and Info

2. Where do we live?2. Where do we live?• A. Our solar system is a A. Our solar system is a

tinytiny part of the Milky Way part of the Milky Way galaxy.galaxy.

• B. Our Solar System B. Our Solar System makes one full orbit every makes one full orbit every 200 million years.200 million years.

• C. Most stars in the Milky C. Most stars in the Milky Way are too close Way are too close together / far away to see together / far away to see individually individually (milky look).(milky look).

Our Home: Our Home: The Milky The Milky

Way GalaxyWay Galaxy

WeWe are always in motion….. are always in motion…..

66,600 mi/hr66,600 mi/hr

483,000 mi/hr483,000 mi/hr

1.3 Million mi/hr1.3 Million mi/hr

Most of these points of light Most of these points of light are within our own galaxy, but are within our own galaxy, but some points of light are some points of light are actually other galaxies….actually other galaxies….

3. Parts of a Galaxy3. Parts of a Galaxy

FYI ~ The center of the Milky Way lies in the constellation of Sagittarius. When observations were made of the stellar velocities in the area, they were found to be particularly fast, which suggests that there is a high gravitational force acting on the stars, and therefore a high mass object in the center. This is now believed to be a black hole. 

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4. Types of Galaxies4. Types of Galaxies

A. A. SpiralSpiral – flat disk, spiral – flat disk, spiral arms, bulging centerarms, bulging center

B. Elliptical- round to oval

C. Irregular – lack a distinct shape (likely due to gravitational influence of other nearby galaxies)

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5. Our Next Door Neighbor5. Our Next Door NeighborA. Andromeda Galaxy (a.k.a Messier 31 or M31) - nearest spiral galaxy to our own , approx. 2.5 million L.Y. away

B. Location – visible with just your eyes in the constellation Andromeda

Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy and about 30 other smaller galaxies. The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (1012) stars.The Milky Way and Andromeda galaxies are expected to The Milky Way and Andromeda galaxies are expected to collide / merge in ~ 3.75 billion years.collide / merge in ~ 3.75 billion years.