Nowadays the more powerful method to detect extrasolar planets is the transit method, that is to say observations of the stellar luminosity regularly decreasing when the planet is transiting the star. We review the planet transits which were anticipated and searched and the first ones which were observed all through history.
Indeed transits of planets in front of their star were first investigated and studied in the Solar System, concerning the star Sun. The first observations of sunspots were sometimes mistaken for transits of unknown planets. The first scientific observation and study of a transit in the Solar System was the observation of Mercury transit by Pierre Gassendi in 1631. Because observations of Venus transits could give a way to determine the distance Sun-Earth, transits of Venus were overwhelmingly observed. Some objects which actually do not exist were searched by their hypothetical transits on the Sun, as some examples a Venus satellite and an infra-mercurial planet. We evoke the possible first use of the hypothesis of an exoplanet transit to explain some periodic variations of the luminosity of a star, namely, the star Algol, during the eighteenth century.
Then we review the predictions of detection of exoplanets by their transits, those predictions being sometimes ancient and made by astronomers as well as popular science writers. However, these very interesting predictions were never published in peer-reviewed journals specialized in astronomical discoveries and results.
A possible transit of the planet β Pic b was observed in 1981. Shall we see another transit expected for the same planet during 2018?
Nowadays, some studies of transits which are connected to hypothetical extraterrestrial civilizations are published in astronomical peer-reviewed journals. So we can note that the discovery of exoplanets is modiying in the research methods of astronomers. Some studies which would be classified not long ago as science fiction are now considered as scientific ones.
This is a preview of subscription content, log in to check access.
Fontenelle BLB d (1686) Entretien sur la Pluralité des Mondes. Vve. Blageart C, Paris [English translation used here: (1803) Conversations on the plurality of worlds. translated by Gunning E, Cundee, London]Google Scholar
Galilei G (1613) Istoria e dimostrazioni intorno alle macchie solari. Giacomo Mascardi, RomaGoogle Scholar
Gassendi P (1632) Mercurius in sole visus, et Venus invisa Parisiis, anno 1631. Sébastien Cramoisy, ParisGoogle Scholar
Goodricke (1783) A series of observations on, and a discovery of, the period of the variation of the light of a bright star in the head of medusa, called Algol. Phil Trans R Soc London 73:474–482CrossRefGoogle Scholar
Huygens C (1698) Kosmotheoros: sive de terris coelestibus, earumque ornatu conjecturae. Den Haag [English translation: The celestial worlds discovered: or, conjectures concerning the inhabitants, plants and productions of the worlds in the planets. London]Google Scholar