TRITON: THE LARGEST NATURAL SATELLITE OF NEPTUNE

The Grandma & Joseph in the Ebre Observatory

Joseph de Ca'th Lon has invited The Grandma to spend some days in the Ebre lands. He wants to go to the Ebre Observatory with her to talk about Triton, the Neptune's moon that was discovered on a day like today in 1846.

During the travel to Roquetes, where the Ebre Observatory is located, The Grandma has studied a new lesson of her First Certificate Language Practice manual (Vocabulary 7).

She has been also thinking in her Majorcan friends, especially on a day like today, where they are suffering the terrible consequences of an enormous flood with mortal victims and many scenes of desolation. The Grandma's heart and her thoughts are today in this wonderful and special island, and with its people, who always accompanies her wherever she goes.

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Triton is the largest natural satellite of the planet Neptune and the first Neptunian moon to be discovered on October 10, 1846 by English astronomer William Lassell.

It is the only large moon in the Solar System with a retrograde orbit, an orbit in the direction opposite to its planet's rotation. It is 2,710 kilometres in diameter, the seventh-largest moon in the Solar System.

Triton is thought to have been a dwarf planet captured from the Kuiper belt because of its retrograde orbit and composition similar to Pluto's. It has a surface of mostly frozen nitrogen, a mostly water-ice crust, an icy mantle, and a substantial core of rock and metal. The core makes up two-thirds of its total mass. It has a mean density of 2.061 g/cm3  and is composed of approximately 15–35% water ice.

Triton

Triton is one of the few moons in the Solar System known to be geologically active, the others being Jupiter's Io and Europa, and Saturn's Enceladus and Titan.

As a consequence, its surface is relatively young with few obvious impact craters, and a complex geological history revealed in intricate cryovolcanic and tectonic terrains. Part of its surface has geysers erupting sublimated nitrogen gas, contributing to a tenuous nitrogen atmosphere less than 1/70,000 the pressure of Earth's atmosphere at sea level. It is the second-largest planetary moon in relation to its primary, after Earth's moon. 

Triton was discovered by British astronomer William Lassell on October 10, 1846, just 17 days after the discovery of Neptune. He discovered Triton with his self-built, 61 cm telescope.

A brewer by trade, Lassell began making mirrors for his amateur telescope in 1820. When John Herschel received news of Neptune's discovery, he wrote to Lassell suggesting he search for possible moons. Lassell did so and discovered Triton eight days later. Lassell also claimed to have discovered rings. Although Neptune was later confirmed to have rings, they are so faint and dark that it is doubtful that he actually saw them.

More information: Observatori de l'Ebre

Triton is named after the Greek sea god Triton or Τρίτων, the son of Poseidon, the Greek god comparable to the Roman Neptune. The name was first proposed by Camille Flammarion in his 1880 book Astronomie Populaire, and was officially adopted many decades later.

Until the discovery of the second moon Nereid in 1949, Triton was commonly referred to as the satellite of Neptune. Lassell did not name his own discovery; he later successfully suggested the name Hyperion, previously chosen by John Herschel, for the eighth moon of Saturn when he discovered it.

The surface of Triton

Moons in retrograde orbits cannot form in the same region of the solar nebula as the planets they orbit, so Triton must have been captured from elsewhere.

It might therefore have originated in the Kuiper belt, a ring of small icy objects extending from just inside the orbit of Neptune to about 50 AU from the Sun. 

Thought to be the point of origin for the majority of short-period comets observed from Earth, the belt is also home to several large, planet-like bodies including Pluto, which is now recognized as the largest in a population of Kuiper belt objects, the plutinos, locked in orbital step with Neptune.

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Triton is only slightly larger than Pluto and nearly identical in composition, which has led to the hypothesis that the two share a common origin.

The proposed capture of Triton may explain several features of the Neptunian system, including the extremely eccentric orbit of Neptune's moon Nereid and the scarcity of moons as compared to the other giant planets.

Triton's initially eccentric orbit would have intersected orbits of irregular moons and disrupted those of smaller regular moons, dispersing them through gravitational interactions.

Triton's eccentric post-capture orbit would have also resulted in tidal heating of its interior, which could have kept Triton fluid for a billion years; this inference is supported by evidence of differentiation in Triton's interior. This source of internal heat disappeared following tidal locking and circularization of the orbit.

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Man is a microcosm, or a little world, because he is an extract 

from all the stars and planets of the whole firmament, 

from the earth and the elements; and so he is their quintessence.

Paracelsus