page_title: Extraterrestrial sky
section_title: The sky of Triton
hierarchical_section_title: Extraterrestrial sky / Neptune / The sky of Triton
caption_attribution_description: Simulated view of Neptune as seen from the surface of Triton.
context_page_description: In astronomy, an extraterrestrial sky is a view of outer space from the surface of an astronomical body other than Earth.
  The only extraterrestrial sky that has been directly observed and photographed by astronauts is that of the Moon. The skies of Venus, Mars and Titan have been observed by space probes designed to land on the surface and transmit images back to Earth.
  Characteristics of extraterrestrial sky appear to vary substantially due to a number of factors. An extraterrestrial atmosphere, if present, has a large bearing on visible characteristics. The atmosphere's density and chemical composition can contribute to differences in colour, opacity and the presence of clouds. Astronomical objects may also be visible and can include natural satellites, rings, star systems and nebulas and other planetary system bodies.
context_section_description: Triton, Neptune's largest moon, has an atmosphere, but it is so thin that its sky is still black, possibly with some pale haze at the horizon. Because Triton orbits with synchronous rotation, Neptune always appears in the same position in its sky. Triton's rotation axis is inclined 130° to Neptune's orbital plane and thus points within 40° of the Sun twice per Neptunian year, much like Uranus's. As Neptune orbits the Sun, Triton's polar regions take turns facing the Sun for 82 years at a stretch, resulting in radical seasonal changes as one pole, then the other, moves into the sunlight.
  Neptune itself would span 8 degrees in Triton's sky, though with a maximum brightness roughly comparable to that of the full moon on Earth it would appear only about ​¹⁄₂₅₆ as bright as the full moon, per unit area. Due to its eccentric orbit, Nereid would vary considerably in brightness, from fifth to first magnitude; its disk would be far too small to see with the naked eye. Proteus would also be difficult to resolve at just 5–6 arcminutes across, but it would never be fainter than first magnitude, and at its closest would rival Canopus.
caption: Neptune in the sky of Triton (simulated view)
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