Editing Extraterrestrial sky (section)

==Venus==
The atmosphere of [[Venus]] is so thick that the Sun is not distinguishable in the daytime sky, and the [[star]]s are not visible at night. Being closer to the Sun, Venus receives about 1.9 times more sunlight than Earth, but due to the thick atmosphere, only about 20% of the light reaches the surface.<ref>{{cite news |url=https://www.seti.org/press-release/possible-venus-twin-discovered-around-dim-star |title=Possible Venus twin discovered around dim star |date=April 6, 2017 |publisher=SETI Institute}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=IMkSBAAAQBAJ&dq=%22block+out+80+per+cent+of+all+sunlight%22&pg=PA62|title=The Planets: The Definitive Visual Guide to Our Solar System|date=1 September 2014|publisher=Dorling Kindersley Limited|isbn=978-0-241-18676-3 |accessdate=6 October 2023|via=Google Books}}</ref> Color images taken by the Soviet [[Venera program|Venera]] probes suggest that the sky on Venus is [[Orange (color)|orange]].<ref>{{cite web |url=http://solarsystem.nasa.gov/missions/venera_13/ |title=Venera 13 – Missions – NASA Solar System Exploration |website=NASA Solar System Exploration |access-date=December 22, 2015 |archive-date=March 6, 2016 |archive-url=https://web.archive.org/web/20160306023924/http://solarsystem.nasa.gov/missions/venera_13/ |url-status=dead }}</ref> If the Sun could be seen from Venus's surface, the time from one sunrise to the next (a [[solar day]]) would be 116.75 Earth days. Because of Venus's [[retrograde motion|retrograde rotation]], the Sun would appear to rise in the west and set in the east.<ref>{{cite web |url=http://www.planetary.org/explore/topics/compare_the_planets/terrestrial.html |archive-url=https://web.archive.org/web/20110728044444/http://www.planetary.org/explore/topics/compare_the_planets/terrestrial.html |archive-date=28 July 2011 |title=The Terrestrial Planets |publisher=The Planetary Society |access-date=3 August 2007 |url-status=dead }}</ref>

An observer aloft in Venus's cloud tops, on the other hand, would circumnavigate the planet in about four Earth days and see a sky in which Earth and the Moon shine brightly (about magnitudes −6.6<ref name="Perelman" /> and −2.7, respectively) at [[opposition (planets)|opposition]]. The maximum angular separation between the Moon and Earth from the perspective of Venus is 0.612°, or approximately the same separation of one centimetre of separation at a distance of one metre and coincidentally, about the apparent size of the Moon as seen from Earth. Mercury would also be easy to spot, because it is closer and brighter, at up to magnitude −2.7,<ref name="Perelman" /> and because its maximum [[Elongation (astronomy)|elongation]] from the Sun is considerably larger (40.5°) than when observed from Earth (28.3°).

[[42 Draconis]] is the closest star to the north pole of [[Venus]]. [[Eta¹ Doradus]] is the closest to its south pole. (Note: The IAU uses the [[right-hand rule]] to define a ''positive pole'' for the purpose of determining orientation. Using this convention, Venus is tilted 177° ("upside down"), and the positive pole is instead the south pole.)<ref>{{Cite journal
| doi = 10.1007/s10569-010-9320-4
| title = Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009
| url = http://astropedia.astrogeology.usgs.gov/alfresco/d/d/workspace/SpacesStore/28fd9e81-1964-44d6-a58b-fbbf61e64e15/WGCCRE2009reprint.pdf <!--
| url = http://astropedia.astrogeology.usgs.gov/download/Docs/WGCCRE/WGCCRE2009reprint.pdf -->
| journal = Celestial Mechanics and Dynamical Astronomy
| volume = 109 | issue = 2 | pages = 101–135
| year = 2010
| last1 = Archinal | first1 = Brent A.
| last2 = A'Hearn | first2 = Michael F.
| last3 = Bowell | first3 = Edward G.
| last4 = Conrad | first4 = Albert R.
| last5 = Consolmagno | first5 = Guy J.
| display-authors = 5
| last6 = Courtin | first6 = Régis
| last7 = Fukushima | first7 = Toshio
| last8 = Hestroffer | first8 = Daniel
| last9 = Hilton | first9 = James L.
| last10 = Krasinsky | first10 = George A.
| last11 = Neumann | first11 = Gregory A.
| last12 = Oberst | first12 = Jürgen
| last13 = Seidelmann | first13 = P. Kenneth
| last14 = Stooke | first14 = Philip J.
| last15 = Tholen | first15 = David J.
| last16 = Thomas | first16 = Paul C.
| last17 = Williams | first17 = Iwan P.|bibcode = 2011CeMDA.109..101A | s2cid = 189842666
| url-access = subscription
}}</ref>