William Lassell FRS (18 June 1799 – 5 October 1880) was an English merchant and astronomer.
Born in Bolton, a town west of Manchester, and educated in Rochdale. After the death of his father, he was apprenticed from 1814 to 1821 to a merchant in Liverpool. He then made his fortune as a beer brewer, which enabled him to indulge his interest in astronomy. He built an observatory at his house…
William Lassell FRS (18 June 1799 – 5 October 1880) was an English merchant and astronomer.
Born in Bolton, a town west of Manchester, and educated in Rochdale. After the death of his father, he was apprenticed from 1814 to 1821 to a merchant in Liverpool. He then made his fortune as a beer brewer, which enabled him to indulge his interest in astronomy. He built an observatory at his house…
William Lassell FRS (18 June 1799 – 5 October 1880) was an English merchant and astronomer.
Born in Bolton, a town west of Manchester, and educated in Rochdale. After the death of his father, he was apprenticed from 1814 to 1821 to a merchant in Liverpool. He then made his fortune as a beer brewer, which enabled him to indulge his interest in astronomy. He built an observatory at his house “Starfield” in West Derby, a suburb of Liverpool.
There he had a 24-inch (610 mm) reflector telescope, for which he pioneered the use of an equatorial mount for easy tracking of objects as the Earth rotates. He ground and polished the mirror himself, using equipment he constructed. The observatory was later (1854) moved further out of Liverpool, to Bradstone.
In 1846 Lassell discovered Triton, the largest moon of Neptune, just 17 days after the discovery of Neptune itself by German astronomer Johann Gottfried Galle. In 1848 he independently co-discovered Hyperion, a moon of Saturn. In 1851 he discovered Ariel and Umbriel, two moons of Uranus.
In 1855, he built a 48-inch (1,200 mm) telescope, which he installed in Malta because of the observing conditions that were better than in often overcast England. On his return to the UK after several years in Malta he moved to Maidenhead and operated his 24-inch (610 mm) telescope in an observatory there.
He won the Gold Medal of the Royal Astronomical Society in 1849, and served as its president for two years starting in 1870. He was also elected a Fellow of the Royal Society in 1849 and won their Royal Medal in 1858.
Lassell died in Maidenhead in 1880. Upon his death, he left a fortune of £80,000 (roughly equivalent to 8.8 million American dollars by today’s standards). His telescope was presented to the Royal Observatory in Greenwich.
The crater Lassell on the Moon, a crater on Mars, the asteroid 2636 Lassell and a ring of Neptune are named in his honour.
Triton is the largest moon of the planet Neptune. It is the only large moon in the Solar System with a retrograde orbit, an orbit in the opposite direction to its planet’s rotation. At 2,700 kilometres (1,700 mi) in diameter, it is the seventh-largest moon in the Solar System.
Because of its retrograde orbit and composition similar to Pluto‘s, Triton is thought to have been captured from the Kui…
Triton is the largest moon of the planet Neptune. It is the only large moon in the Solar System with a retrograde orbit, an orbit in the opposite direction to its planet’s rotation. At 2,700 kilometres (1,700 mi) in diameter, it is the seventh-largest moon in the Solar System.
Because of its retrograde orbit and composition similar to Pluto‘s, Triton is thought to have been captured from the Kui…
Triton is the largest moon of the planet Neptune. It is the only large moon in the Solar System with a retrograde orbit, an orbit in the opposite direction to its planet’s rotation. At 2,700 kilometres (1,700 mi) in diameter, it is the seventh-largest moon in the Solar System.
Because of its retrograde orbit and composition similar to Pluto‘s, Triton is thought to have been captured from the Kuiper belt. Triton 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. Triton has a mean density of 2.061 grams per cubic centimetre (0.0745 lb/cu in) and is composed of approximately 15–35% water ice.
Triton is one of the few moons in the Solar System known to be geologically active. As a consequence, its surface is relatively young, with a complex geological history revealed in intricate cryovolcanic and tectonic terrains. Part of its crust is dotted with geysers thought to erupt nitrogen. Triton has a tenuous nitrogen atmosphere less than 1/70,000 the pressure of Earth’s atmosphere at sea level.
Triton was discovered by British astronomer William Lassell on October 10, 1846, just 17 days after the discovery of Neptune.
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.
Triton is named after the Greek sea god Triton (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, although it was not officially adopted until many decades later. Until the discovery of the second moon Nereid in 1949, Triton was commonly known as simply “the satellite of Neptune”. Lassell did not name his own discovery, although he suggested names a few years after his subsequent discovery of an eighth moon of Saturn (Hyperion).
Triton – Neptune
RINGS OF NEPTUNE
Evidence for incomplete arcs around
Neptune first arose in the mid-1980s, when stellar occultation
experiments were found to occasionally show an extra “blink” just
before or after the planet occulted the star.
Images by Voyager 2 in 1989 settled the issue, when the ring system was
found to contain several faint rings, the outermost of which, named
Adams, contains three prominent arcs now named Liberty, Equality and
Fraternity. The existence of arcs is very difficult to understand
because the laws of motion would predict that arcs spread out into a
uniform ring over very short timescales.
The gravitational effects of Galatea, a moon just inward from the ring,
are now believed to confine the arcs.Several other rings were detected
by the Voyager cameras. In addition to the narrow Adams Ring 63,000 km
from the center of Neptune, the Leverrier Ring is at 53,000 km and the
broader, fainter Galle Ring is at 42,000 km. A faint outward extension
to the Leverrier Ring has been named Lassell; it is bounded at its
outer edge by the Arago Ring at 57,000 km.
Source References: Murray, C. D., and S. F. Dermott 1999. Solar System Dynamics, Cambridge University Press.
RINGS OF NEPTUNE
Evidence for incomplete arcs around
Neptune first arose in the mid-1980s, when stellar occultation
experiments were found to occasionally show an extra “blink” just
before or after the planet occulted the star.
Images by Voyager 2 in 1989 settled the issue, when the ring system was
found to contain several faint rings, the outermost of which, named
Adams, contains three prominent arcs now named Liberty, Equality and
Fraternity. The existence of arcs is very difficult to understand
because the laws of motion would predict that arcs spread out into a
uniform ring over very short timescales.
The gravitational effects of Galatea, a moon just inward from the ring,
are now believed to confine the arcs.Several other rings were detected
by the Voyager cameras. In addition to the narrow Adams Ring 63,000 km
from the center of Neptune, the Leverrier Ring is at 53,000 km and the
broader, fainter Galle Ring is at 42,000 km. A faint outward extension
to the Leverrier Ring has been named Lassell; it is bounded at its
outer edge by the Arago Ring at 57,000 km.
Source References: Murray, C. D., and S. F. Dermott 1999. Solar System Dynamics, Cambridge University Press.
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