Our Galaxy
Type
Barred Spiral (SBbc)
Diameter
87,400 – 100,000 ly
Thickness (disk)
~2,000 ly
Stars
100–400 billion
Age
~13.6 billion years
Sun's distance from center
~26,000 ly
Sun's orbital period
~225–250 Myr
Central black hole
Sagittarius A* (~4M M☉)
Image: NASA/JPL-Caltech/ESO/R. Hurt
Spiral Arms
Perseus Arm
Sagittarius Arm
Scutum-Centaurus Arm
Norma Arm
Orion–Cygnus Spur (our location)
Sun
Real objects
Star size
Only stars with a measured distance are shown — a magnitude-limited sample, so distant stars are mostly luminous giants and the density fading with distance is a selection effect, not the Galaxy thinning out.
Open cluster
Globular cluster
Emission / reflection nebula, supernova remnant
Planetary nebula
Satellite galaxy (LMC, SMC)
