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 colloquially referred to as moons, a deriv ...

s of

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

pass in front of the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

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 separation (in units of angle) describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the ''visual an ...

than the Sun, the proper term would be a

transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1980 film), a 1980 Israeli film * ''Transit'' (1986 film), a Canadian short film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countrie ...

, and for 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 f ...

. Almost 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. The last eclipse on Neptune by Triton occurred in 1953, and the next will be in 2046. 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 of lesser size. In cases of equal or smaller impinging objects, only an umbra and penumba are generated. As ...

. 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 (; ), sometimes also hydriads, 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 embodied ...

, 7–13';

Thalassa Thalassa (; ; 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 and connected to the name of the Mesopotamian primordial sea godde ...

, 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, three different mythological figures from Greek mythology In the arts * '' Aci, Galatea e Polifemo'', ca ...

, 13–18';

Larissa Larissa (; , , ) 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 148,562 in the city proper, according to the 2021 census. It is also the capital of the Larissa ...

, 10–14';

Proteus In Greek mythology, Proteus ( ; ) 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''). Some who ascribe a specific domain to Prote ...

, 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