B
- Baade's Window
- Balmer series
- Bandpass
- Bars
- Baryonic Acoustic Oscillations
- Baryonic Matter
- Baryons
- Baseline
- Be star
- Be X-ray Binaries
- Big Bang
- Big Crunch
- Binary Mass Function
- Binary Pulsars
- Binary Star
- Black Hole
- Blackbody Radiation
- Blue Stragglers
- Bok Globule
- Bolide
- Bolometric Magnitude
- Bremsstrahlung radiation
- Brightest Cluster Galaxies
- Broadband
- Brown Dwarf
- Bulges
- Butcher-Oemler Effect