Heart of the Milky Way - Composite
right|78772da1a3b4b4ac49d06dc9a6d06d2fec0d535f|Milky Way center in 3 Wave Bands|]This first image is of the central region of the Milky Way galaxy and is a composite of three separate images of the same region, each taken in a different wave band. This is the heart of our own megalopolis of stars.
Distance to the center: ~25,000 light years. (And we are in the Milky Way galaxy.)
Mass of the entire Milky Way: estimates range from about 200 billion to 1.9 trillion solar masses. Karachentsev's "Catalog of nearby galaxies" gives 141 billion solar masses.
Diameter of the entire Milky Way: 100,000 light years.
An image from the Spitzer Space Telescope in infrared (IR) was combined with another from the Hubble in near-infrared, and a third image from the Chandra X-ray Observatory.
The image at right shows the three separate images.
Top: reddish clouds from Spitzer (IR).
Middle: golden streaks from Hubble (near-IR).
Bottom: blue and violet clouds from Chandra (X-ray).
Christian, Eric and Safi-Harb, Samar, "Size of the Milky Way ," http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980317b.html
Eisenhauer, F., et al, SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light-Month, http://adsabs.harvard.edu/abs/2005ApJ...628..246E
Evans, N. and Wilkinson, M., "The Mass of the Andromeda galaxy," http://adsabs.harvard.edu/abs/2000MNRAS.316..929E
Karachentsev, I., et al, "Catalog of neighboring galaxies," http://vizier.cfa.harvard.edu/viz-bin/Cat?J/AJ/127/2031