What is Exotic atom?
An '''exotic atom''' is an [[atom]] that has a [[particle]] replaced by a particle of the same [[Charged particle|charge]]. For example, [[Positronium]], an exotic atom, contains an [[electron]] and a [[positron]]. The positron (which is the [[antiparticle]] of the electron) replaces a [[proton]] which would normally be found in that atom. Most exotic atoms are hard to discover, because they decay very quickly. Positronium on average has a [[Half-life (element)|half-life]] (how long until half of the object is gone via decay) of 0.125 nanoseconds. There are a few types of exotic atom. == Muonic atom == A muonic atom is an exotic atom that has a [[muon]], instead of an electron, orbiting the [[Atomic nucleus|nucleus]]. Because a muon is much more massive than an electron, the muon orbits much closer to the nucleus. == Hadronic atom == A hadronic atom is an exotic atom that has an electron replaced by a negatively charged [[hadron]]. The hadron could be a [[meson]] (such as a [[pion]] or a [[kaon]], creating a pionic atom or a kaonic atom, respectively). Another hadronic atom is an [[antiproton]] (antiparticle of the proton) atom, that has an antiproton replacing an electron. This is known as an antiprotonic atom. == Onium == An onium is an exotic atom that has a particle bound to its antiparticle. A good example is Positronium, which is an electron bound to a positron. == Hypernuclear atom == A hypernuclear atom is an exotic atom that contains strange particles (a particle that is made of a strange quark) called [[Hyperon|hyperons]]. ==Related pages== * [[Positronium]] * [[Antimatter]] * [[Atom]] * [[Hadron]] * [[Meson]] [[Category:Nuclear physics]] [[Category:Matter]]