Solar eclipses on Neptune occur when substantial

natural satellite A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'' ...

s of

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

pass in front of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

as seen from the planet. For bodies which appear smaller in

angular diameter The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is ...

than the Sun, the proper term would be a

transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1979 film), a 1979 Israeli film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countries in the world * ''Transit'' (2006 film), a 2006 ...

and bodies which are larger than the apparent size of the Sun, the proper term would be an

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...

. All of Neptune's inner moons and

Triton Triton commonly refers to: * Triton (mythology), a Greek god * Triton (moon), a satellite of Neptune Triton may also refer to: Biology * Triton cockatoo, a parrot * Triton (gastropod), a group of sea snails * ''Triton'', a synonym of ''Triturus' ...

can eclipse the Sun as seen from Neptune. All other satellites of Neptune are too small and/or too distant to produce an

umbra The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast. Th ...

. From this distance, the Sun's angular diameter is reduced to one and a quarter arcminutes across. Here are the angular diameters of the moons that are large enough to fully eclipse the Sun:

Naiad In Greek mythology, the naiads (; grc-gre, ναϊάδες, naïádes) are a type of female spirit, or nymph, presiding over fountains, wells, springs, streams, brooks and other bodies of fresh water. They are distinct from river gods, who ...

, 7–13';

Thalassa Thalassa (; grc-gre, Θάλασσα, Thálassa, sea; Attic Greek: , ''Thálatta'') was the general word for 'sea' and for its divine female personification in Greek mythology. The word may have been of Pre-Greek origin. Mythology According t ...

, 8–14'; Despina, 14–22';

Galatea Galatea is an ancient Greek name meaning "she who is milk-white". Galatea, Galathea or Gallathea may refer to: In mythology * Galatea (Greek myth), three different mythological figures In the arts * ''Aci, Galatea e Polifemo'', cantata by H ...

, 13–18';

Larissa Larissa (; el, Λάρισα, , ) is the capital and largest city of the Thessaly region in Greece. It is the fifth-most populous city in Greece with a population of 144,651 according to the 2011 census. It is also capital of the Larissa regiona ...

, 10–14';

Proteus In Greek mythology, Proteus (; Ancient Greek: Πρωτεύς, ''Prōteus'') is an early prophetic sea-god or god of rivers and oceanic bodies of water, one of several deities whom Homer calls the "Old Man of the Sea" ''(hálios gérôn)''. ...

, 13–16'; Triton, 26–28'. Just because the moons are large enough to fully eclipse the Sun does not necessarily mean that they will do so. Eclipses of the Sun from Neptune are rare due to the planet's long orbital period and large axial tilt of 28 degrees. In addition, the largest moon, Triton, has an orbital inclination of about 25 degrees to Neptune's equator. This makes eclipses of the Sun by Triton rare. Even when such an eclipse does occur, it passes rather quickly, as Triton moves in the opposite direction of Neptune's rotation.

References

{{Neptune Solar eclipses by planet Neptune

See also

References