Lecture 19

Lecture 19 - 1. The Astronomer's Guide to the Galaxy (Milky...

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1. The Astronomer's Guide to the Galaxy (Milky Way) o We live in a fragment of one of the arms o Impossible to look at our galaxy from the outside o Invisible light- blocked by dust o 2 major arms: Perseus and Centauraus o Minor arms: Sagittarius, Cygnus, and Orion (where we live) 2. So is our galaxy really a spiral? o Radio measurements suggest it is o Molecular clouds trace out lines of the arms of the galaxy o This is where stars are being born 3. Galactic Rotation o Keplerian rotation Things further out move more slowly Things inside must rotate faster Rotation speed slows down as you go out o Solid body rotation Outer stars must move faster o How does are galaxy rotate? Somewhere in between these two. .all stars move at about the same speed o Center of our galaxy Ionized gas Dust STARS Where the gravity of the galaxy comes from 4. How long does it take stars closer to the center of the galaxy than the Sun to complete one orbit?
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Lecture 19 - 1. The Astronomer's Guide to the Galaxy (Milky...

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