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The Fundamentals of Galaxies Developed by the Spiral Graph team.
Module 1: The History of Galaxies Key Questions: ● What is a galaxy? ● Where does the term “galaxy” come from? ● What were galaxies first thought to be? ● How were galaxies discovered?
What is a galaxy? ● A galaxy is a gravitationally bound system containing: ○ Stars
What is a galaxy? ● A galaxy is a gravitationally bound system containing: ○ Stars ○ Gas
What is a galaxy? ● A galaxy is a gravitationally bound system containing: ○ Stars ○ Gas ○ Dust
What is a galaxy? ● A galaxy is a gravitationally bound system containing: ○ Stars ○ Gas ○ Dust ○ Dark matter
What is a galaxy? These are examples of different types
Where does the term “galaxy” come from? ● Derived from the Greek galaxías kýklos, or milky wheel / circle ● This is in reference to the Milky Way, our own galaxy, as seen in the sky
Where does the term “galaxy” come from? ● Ancient Greeks believed that the Milky Way was formed from the goddess Hera when she pushed away young Heracles as he was feeding, spilling milk across the sky.
How were galaxies discovered? ● By using a standard candle ○An object with known brightness that can be used to measure distance. ● Henrietta Leavitt discovered a new type of standard candle in 1912.
How were galaxies discovered? ● By using a standard candle ○An object with known brightness that can be used to measure distance. ● Henrietta Leavitt discovered a new type of standard candle in 1912. ○ A category of star called a Cepheid Variable.
How were galaxies discovered? ● Edwin Hubble found Cepheid variables in the Andromeda Nebula in 1924.
How were galaxies discovered? ● Edwin Hubble found Cepheid variables in the Andromeda Nebula in 1924. ○ The measured distances meant that it must be outside the Milky Way. ○ Meaning it is a spiral galaxy, not a spiral nebula.
Module 1 Kahoot!
References Slide 1: NGC 1300 Slide 2: Image Slide 3: Milky Way stars Slide 4: Rosette Nebula gas Slide 5: Rosette Nebula dust Slide 6: Milky Way dark matter halo Slide 7: NGC 2217 (barred spiral), IC 2006 (elliptical), NGC 1232 (non-barred spiral), NGC 4676 (irregular/interacting), NGC 2787 (lenticular) Slide 8: Milky Way picture Slide 9: Hera picture Slide 10: Hera picture Slide 11: Milky Way picture Slide 12: William Parsons and the Leviathan of Parsonstown video Slide 13: Drawings of Whirlpool Galaxy (M51) and M33 by William Parsons Slide 14: HST image of M51 and VLT image of M33, Slide 15: Standard candle diagram Slide 16: Henrietta Leavitt picture Slide 17: Cepheid variable video Slide 18: Edwin Hubble and Copernicus the cat photo Slide 19: Andromeda Galaxy Slide 20: Image This work is licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.
