Antimatter in the Universe : Constraints from Gamma-Ray Astronomy

Understand

We review gamma-ray observations that constrain antimatter - both baryonic and leptonic - in the Universe.

• Antimatter can be probed through ordinary matter, with the resulting annihilation gamma-rays providing indirect evidence for its presence.
• Although it is generally accepted that equal amounts of matter and antimatter have been produced in the Big Bang, gamma-rays have so far failed to detect substantial amounts of baryonic antimatter in the Universe.
• Conversely, positrons are abundantly observed through their annihilation in the central regions of our Galaxy and, although a wealth of astrophysical sources are plausible, their very origin is still unknown.