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Why is the carbon-carbon triple bond in acetylene especially short?

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structures of common hydrocarbon compounds — hydrocarbon Structures assumed by hydrogen (H) and carbon (C) molecules in four common hydrocarbon compounds.

The carbon-carbon triple bond in acetylene is exceptionally short—measuring 1.20 angstroms—primarily due to the nature of the hybridization of the carbon atoms involved.1

In acetylene, each carbon atom is sp hybridized. This hybridization involves the mixing of one s orbital and one p orbital, resulting in two equivalent sp hybrid orbitals. Because these orbitals have a higher percentage of s-character compared to the sp² hybrids found in ethylene or the sp³ hybrids in ethane, the electrons are held more closely to the carbon nucleus, which naturally draws the bonded atoms closer together.23

Furthermore, the triple bond itself consists of one strong sigma ( $σ$ ) bond and two pi ( $π$ ) bonds formed by the overlap of two remaining p orbitals on each carbon. The presence of these multiple bonding components, combined with the compact nature of the sp hybrid orbitals, results in a significantly shorter and stronger bond distance than those found in double or single carbon-carbon bonds.21