Lecture 31 – Structure of the Milky Way. Let’s check our answer Are there other objects in the sky which resemble the MW?

M31 The Andromeda Galaxy

M104 The Sombrero Galaxy

The Sky is filled with objects with the same shape and size of the Milky Way. The term for these objects is spiral galaxy. So we figured out the structure of the MW pretty well from the inside, and there is a universe filled with similar objects

Next topic: motions of stars in galaxies There are internal motions In galaxies, a “procession of stars”. How can we tell?

The Doppler Effect (p104) If a source of waves is in motion with respect to an observer, the observer measures a different wavelength than was emitted

The Doppler Effect: Say it in equations W-W0 V W0 c DEMO

How the Doppler Effect effects spectral lines

Results for the motion of the Sun in the Milky Way Doppler shifts measured for many objects outside the Milky Way, or not a part of the galactic disk. The Sun is moving on an orbit around the galactic center at a speed of V=220 km/sec The motion of our orbit is in the direction of Cygnus

An independent proof that the Sun is moving on an orbit in the Milky Way DEMO VLBI observations