John Couch Adams, English mathematician and astronomer who used
mathematics to predict the orbit of the planet Neptune, was born on this date in 1819. Here are ten facts about his famous discovery.

Neptune's
mass is 1.0243×1026 kg, 17 times that of Earth. It is the
fourth-largest planet in the solar system and the farthest from the
sun since Pluto was demoted.
It
can't be seen with the naked eye from Earth and was therefore the
first to be discovered using mathematics and observing its effect on
its neighbour, Uranus. In 1821, Alexis Bouvard published
astronomical tables of the orbit of Uranus, but he then found
substantial deviations from his tables, and hypothesised that
something else was out there, exerting its gravitational force on
Uranus. In the 1840s, both John Couch Adams and a French astronomer,
Urbain Le Verrier worked out the orbit of the new planet
mathematically but at first nobody was very interested. Eventually,
Adams persuaded Cambridge Observatory director James Challis to look
for it with a telescope but he didn't find anything. Meanwhile, Le
Verrier wrote to Berlin Observatory astronomer Johann Gottfried
Galle persuading him to try. He received the letter on 23 September
1846, and that very evening got his telescope out and found Neptune,
pretty much exactly where Le Verrier said it would be.
This
led to some argument between England and France over who should get
the credit for the discovery. At the time, it was decided they
should share the credit, but following a review of the documents the
"Neptune papers" the verdict was that Le Verrier should
get most of the credit.
It
was Le Verrier who suggested the name Neptune (the Roman god of the
sea) for the planet then known as "the planet exterior to
Uranus". Other suggestions were Janus (from Galle) and Oceanus
(from Challis). For a while, Le Verrier proposed naming the planet
after himself, but nobody outside France was keen on this idea.
Neptune is so called in most languages, and in the languages which
call it by a different name, the sea god theme is maintained. In
Chinese, Japanese, and Korean, the planet's name was translated as
"sea king star"; In Mongolian, Neptune is called Dalain
Van after the Mongolian ruler of the sea; In modern Greek the planet
is called Poseidon, the Greek counterpart of Neptune. In Māori, it
is Tangaroa, the Māori god of the sea; in Nahuatl, it's
Tlāloccītlalli, after the rain god Tlāloc. In Hebrew, it's called
Rahab, after a sea monster mentioned in the Bible.
Neptune
has rings, although they are less obvious than Saturn's. The rings
look slightly red and so it's thought they are made of ice particles
coated with silicates or carbon-based material. Le Verrier may not
have managed to get the planet named after him, but one of the rings
bears his name. Other rings are named for Galle and Adams.
Neptune
takes 164.8 years to orbit the Sun.
Neptune
has 14 moons - that we know about. A new moon was discovered in
2013. It doesn't have a name yet; it's currently referred to as
S/2004 N 1, but names are being considered and it will likely be
named after a minor sea god like the other moons. The largest, and
first to be discovered is Triton. Triton was discovered by William
Lassell (who also has a part of the planet's ring system named after
him) 17 days after the discovery of Neptune itself. Triton accounts
for over 99% of the mass in orbit around the planet and is the only
moon of Neptune big enough to be a sphere. The other moons include
Nereid, Proteus, Naiad, Thalassa, Despina, Galatea and Larissa.
The
core of Neptune is composed of Iron, nickel and silicates. The upper
atmosphere is 80% hydrogen and 19% Helium with a trace amount of
methane. Increasing concentrations of methane, ammonia and Water are found in the lower atmosphere.
Winds
on Neptune travel at almost 600 m/s (2,200 km/h; 1,300 mph), twice
the speed of a high speed jet.
Its
astronomical symbol is ♆, a stylised version of Neptune's trident.
It is the ruling planet of Pisces and of Friday, and associated in
astrology with sensitivity, idealism and compassion, illusion,
confusion, and deception. Neptune governs hospitals, prisons, mental
institutions, and any other place, such as a monastery, where people
might go to retreat from society. In astrological medicine, it rules
the thalamus, the spinal canal, and severe or mysterious illnesses
and neuroses. Its appearance in the sky is linked by astrologers
with historical events such as the discovery of anaesthetics and
hypnotism; the rise of nationalist movements seeking independence in
countries throughout Europe; the rise of socialism, the beginnings
of the welfare state and the publication of Marx and Engels' 'The
Communist Manifesto' in 1848.