Halley's Comet, also known as 1P/Halley, is a short-period comet visible from Earth every 74 to 79 years. It is believed to be the only comet that can appear around twice in a human lifetime. The last pass of Halley's Comet was in 1986 and will re-appear in 2061.
- https://web.archive.org/web/20171123064132/http://cometography.com/pcomets/001p.html, http://adsabs.harvard.edu/abs/1986JRASC..80...62Y, https://doi.org/10.1093%2Fmnras%2F197.3.633
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