Editing Venus (section)

=== Transits ===
{{Main|Transit of Venus}}
[[File:Transit of Venus viewed in Wagga Wagga (2).jpg|alt=White disk with a small black dot projected on a screen|left|thumb|upright=0.75|[[2012 transit of Venus]], projected by a [[telescope]] onto a white card]]

A [[transit (astronomy)|transit]] of Venus is the appearance of Venus in front of the Sun, during [[inferior conjunction]]. Since the orbit of Venus is slightly inclined relative to Earth's orbit, most inferior conjunctions with Earth, which occur every [[synodic period]] of 1.6 years, do not produce a transit of Venus. Consequently, Venus transits only occur when an inferior conjunction takes place during some days of June or December, when the orbits of Venus and Earth cross a straight line with the Sun.<ref name="NASA 2004">{{cite web | title=2004 and 2012 Transits of Venus | website=NASA | date=8 June 2004 | url=https://eclipse.gsfc.nasa.gov/transit/venus0412.html#:~:text=Transits%20of%20Venus%20are%20only,121.5%2C%208%20and%20105.5%20years. | access-date=2 May 2023 | archive-date=2 May 2023 | archive-url=https://web.archive.org/web/20230502134029/https://eclipse.gsfc.nasa.gov/transit/venus0412.html#:~:text=Transits%20of%20Venus%20are%20only,121.5%2C%208%20and%20105.5%20years. | url-status=live }}</ref> This results in Venus transiting above Earth in a sequence currently of {{val|8|u=years}}, {{val|105.5|u=years}}, {{val|8|u=years}} and {{val|121.5|u=years}}, forming cycles of {{val|243|u=years}}.

Historically, transits of Venus were important, because they allowed astronomers to determine the size of the [[astronomical unit]], and hence the size of the Solar System as shown by [[Jeremiah Horrocks]] in [[Transit of Venus, 1639|1639 with the first known observation]] of a Venus transit (after history's first observed planetary [[Transit of Mercury|transit in 1631, of Mercury]]).<ref name=Kollerstrom_1998/>

Only seven Venus transits have been observed so far, since their occurrences were calculated in the 1621 by [[Johannes Kepler]]. [[Captain Cook]] sailed to [[Tahiti]] in 1768 to record the third observed transit of Venus, which subsequently resulted in the exploration of the east coast of Australia.<ref name=Hornsby_1771/><ref name=Woolley_1969/>

The latest pair was [[Transit of Venus, 2004|June 8, 2004]] and [[Transit of Venus, 2012|June 5–6, 2012]]. The transit could be watched live from many online outlets or observed locally with the right equipment and conditions.<ref name=Boyle_2016/> The preceding pair of transits occurred in [[Transit of Venus, 1874|December 1874]] and [[Transit of Venus, 1882|December 1882]].

The next transit will occur in December 2117 and December 2125.<ref name=Espenak_2004/>