Baryon Acoustic Oscillations

A preferred ~500-million-light-year separation in the clustering of galaxies, frozen in from sound waves in the early Universe.

Before recombination, pressure waves rippled through the hot plasma. When the Universe became neutral, these waves froze, leaving a subtle preferred distance between galaxies that acts as a 'standard ruler' for measuring cosmic expansion across time.

• Detected in the galaxy clustering of SDSS (2005) and mapped in detail by DESI

• Depends onRecombination
• Related toDark Energy
• Related toThe Expansion of the Universe
• Part of modelThe Lambda-CDM Model
• Measured bySloan Digital Sky Survey
• Measured byDESI (Dark Energy Spectroscopic Instrument)
• Related toLarge-Scale Structure
• Associated withCMB Measurements