# Inventory of the Galactic Center

How do we study the center of the Galaxy?
• 28 magnitudes of optical extinction -- can't do it in visible light
• infrared emission (2.2 microns - K band)
• much less obscured
• old Population I red giants (T ~ 4000 K) are brightest in the infrared.
• unobscured
• not emission from stars
• non-thermal emission (synchrotron emission, supernovae, etc)
At the distance of the Galactic Center, 1" is about 0.05 parsecs.

What do we see?

A rising density of stars towards the center: $\rho\left(r\right)$ ~ r-2 from 1 parsec to 0.1 parsec. Stars are very close together, so close interactions are common.

Lots of non-thermal synchrotron radio emission showing ionized gas and magnetic fields:

The brightest radio source is called Sagittarius A (Sgr A). Sgr A is not a single object, but a complex region at the center of the Galaxy:

• Sgr A East (left side, light blue) is hot explosion remnant, perhaps from a supernova or something else?
• Sgr A West (center, red) is a region of ionized gas which shows a mini-spiral pattern
• Sgr A* is a very bright, compact radio source located in the center of Sgr A West.