What Makes Up Our Galaxy

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Dadark matter halo

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Dark Matter: A Major Problem for Contemporary Physics and Astronomy

Stars are a small fraction of the mass of major galaxies

The dark matter problem becomes more pronounced as you go out in the universe

The form of the dark matter is unknown; probably not what you studied in chemistry

Possibly/probably an unknown form of elementary particle

Slide 16

At the Very Center

Slide 17

What do we see at the galactic center (radio and infrared wavelengths?

Strong radio source (synchrotron radiation)

At infrared wavelengths, can see stars orbiting very vast around Sgr A

Ten years of observations speeded up

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The Orbit of Star S2

Slide 19

Star S2 passes about as close to Sagittarius A* as the planet Pluto passes to the Sun. Indicates supermassive object in a very small region