
The antimatter counterpart of hydrogen, composed of an antiproton and a positron, which annihilates on contact with hydrogen.Antihydrogen is the antimatter counterpart of hydrogen: instead of a proton and an electron, it consists of an antiproton and a positron. It is electrically neutral, like ordinary hydrogen, and is expected to have nearly identical spectral properties, but with key symmetries reversed. When antihydrogen meets ordinary matter, both annihilate completely, converting their mass into energy — a process that makes storing and studying it extremely challenging.
The first antihydrogen atoms were produced at CERN in 1995, but they were fast-moving and annihilated immediately. In 2010, the ALPHA collaboration succeeded in trapping antihydrogen atoms for the first time, and in 2011 they held them for over 15 minutes.
Antihydrogen is produced by combining antiprotons and positrons in a low-temperature trap. Because antimatter annihilates on contact with normal matter, the particles must be held in a vacuum and confined using magnetic fields — antihydrogen atoms are neutral, but their magnetic moments allow them to be trapped in an inhomogeneous field. Once formed, the atoms can be held for minutes or hours, long enough to probe their internal structure with lasers or microwaves.
Antihydrogen is used to test fundamental symmetries of physics, particularly CPT symmetry, by comparing the spectral lines of hydrogen and antihydrogen to extreme precision.
A single gram of antihydrogen annihilating with ordinary matter would release energy equivalent to about 43 kilotons of TNT — roughly the yield of the Hiroshima bomb.









