StarTalk - George's Anus

I love talking about astronomy. It is fascinating and wraps science, history, mythology, mathematics, and culture into one brilliant package. StarTalk is a podcast by Dr Neil deGrasse Tyson and some other hosts. 

The episode I came across today that tickled my fancy is about how the planets and moons in our solar system got their names, the exceptions to the rule, and the reasons why. The episode featured Mr Chuck Nice, a comedian who asked questions we non-professional astronomers would love to ask and made them funny and easy for the common person to understand.

The International Astronomical Union (IAU) has been the body responsible for naming astronomical bodies since its inception in 1919. It followed a rule for naming the planets. Because we have known them since antiquity, it uses their Latin names, as in other fields like medicine and chemistry. The Romans knew of seven bright objects in the sky: the Sun, the Moon, and the five brightest planets. They named them after their most important gods. The planets from Mercury to Saturn are all visible to the naked eye and were named by the Greeks and, later, the Romans; hence, we kept their Roman names and the rich mythology that goes with them. 

Mercury got its name because it was fast, the closest planet to the Sun, and the smallest in our Solar System. Mercury orbits the Sun so fast that it completes one orbit in only 88 days. Pictures show a planet without an atmosphere with numerous craters on its surface. In Roman mythology, Mercury is the messenger of the gods. The Greek name is Hermes. The next planet is Venus; although it's more than 50 million kilometres farther from the Sun than Mercury, its surface temperature is far hotter due to a runaway greenhouse effect. Venus is very shiny because highly reflective clouds blanket it. Venus's clouds contain sulfuric acid droplets and acidic crystals suspended in a gas mixture. Light bounces quickly off the smooth surfaces of these spheres and crystals. This beauty in the sky could kill you in seconds. The Soviets sent four probes to this hellish planet from 1971 to 1985 and sent back pictures. These pictures depicted a hellish, rocky environment. Venus is the Roman goddess of love, and its Greek equivalent is Aphrodite. Mars is orange-red because its soil contains iron oxide, or rust. The planet was named Mars, the Roman god of War, because of its blood-red colour. Mars's surface is red and rocky, but we understand Mars better from the numerous probes sent there. Mars once had liquid water running on its surface and a big sea. Water still exists underground and as ice in the polar regions. Microbial life might exist on Mars. Its Greek equivalent name for the god of War is Ares. The four innermost planets, Mercury, Venus, Earth and Mars, are known as Rocky (Terrestrial) planets. The outer group of planets, Jupiter, Saturn, Uranus, and Neptune, are much larger and are composed mainly of gases, Hydrogen and Helium. These outer planets are known as the Gas giants. Between the inner and outer planets, i.e. Mars and Jupiter, are numerous rocks, asteroids and "minor planets" floating in a group known as the Asteroid Belt. Then, because of its immense size, Jupiter was named after the King of the gods. It is the biggest planet in our Solar System. It has a diameter of 88,695 miles (142,800 kilometres), more than 11 times Earth's diameter. Its volume is over 1,300 times that of Earth. Jupiter is significant not only for its enormous size, but also for the powerful radio waves it emits. These waves can destroy any unprotected probes that pass near it. It also has a Great Red Spot, a storm of massive proportions. This storm has existed since it was first noticed and has lasted more than 300 years. The Greek equivalent of Jupiter is Zeus. The next planet is named Saturn, after the Roman god of Agriculture. Saturn is the only planet with visible rings. The Greek equivalent is Cronus. The next planet and the other planets' moons were discovered with the telescope.

People had observed Uranus many times before recognising it as a planet, but they generally mistook it for a star. Sir William Herschel observed Uranus on 13 March 1781, from the garden of his house at 19 New King Street in Bath, Somerset, England. He presented his findings to the Royal Society and named it Georgium Sidus (George's Star), or the "Georgian Planet", in honour of his patron, King George III. Uranus is tilted on its side, and this unique tilt makes Uranus appear to spin on its side. It takes 84 years to make one rotation around the Sun. The comedian said it would have been known as Georgie's Anus. But the powers that be chose Uranus, after the ancient Greek sky god. As a "consolation prize" for the English, Uranus's moons were named after characters in plays by the famous English author William Shakespeare. 

Io, Callisto, Europa, and Ganymede are known as the Galilean moons because Italian astronomer Galileo Galilei first observed them in 1610 while observing Jupiter. He was the first to identify them (or at least record that he had). The movement of these moons around Jupiter and the observation of Jupiter around the Sun were responsible for Galileo's conviction of the Heliocentric universe, according to Nicolaus Copernicus, a Polish priest, who published in his book De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres) just before his death in 1543. Galileo also published a book titled " Dialogue Concerning the Two Chief World Systems" (1632). The moons of Jupiter are all Greek characters associated with Jupiter (Zeus). Io was regarded as Hera's first priestess and Zeus's wife. Zeus fell in love with her and, to protect her from Hera's wrath, turned her into a white heifer. Callisto was a nymph and Artemis's follower. Zeus developed an attraction to Callisto and turned himself into Artemis to lure Callisto. Zeus sees the young Europa, falls in love with her beauty, and seduces her. To keep the young princess from being frightened by his divine presence, Zeus takes the form of a bull and joins Europa's herd. Ganymede was an exceedingly handsome, aristocratic young Trojan whom Zeus abducted to become his cupbearer. Their moons also have interesting stories. Io is the most volcanically active world in the Solar System, with hundreds of volcanoes, some erupting lava fountains due to the pressures from Jupiter. Jupiter's second-largest moon and the third-largest moon in our solar system. Its surface is the most heavily cratered of any object in our solar system. Europa has another exciting story. It is the smoothest known object in the Solar System, lacking large-scale features such as mountains and craters. The surface's apparent youth and smoothness have led to the hypothesis that a water ocean exists beneath it, which could conceivably harbour extraterrestrial life. It has been observed ejecting plumes of liquid water into space. Then, there is Ganymede, the largest moon in the solar system. This icy world is the only moon with a magnetic field, and the atmospheric auroras that come with it. Then there are up to 60 more, bringing Jupiter's moon count to 64, and they keep finding more. Mars has Phobos and Deimos, always presenting the same face to their planet. Both are lumpy, heavily cratered, and covered in dust and loose rocks, and some scientists believe they were captured asteroids. In mythology, both were sons of Ares and Aphrodite. Phobos is the god and personification of fear and panic in Greek mythology. Deimos is the personal god of dread and terror. Venus and Mercury have no moons because they orbit so close to the Sun. Some believe the Sun's gravity pulled their moons away. Saturn has the second-largest moon in our solar system, Titan. Although very cold, Titan has rivers and oceans of liquid water. Scientists believe the water is liquid because it has a salty liquid layer, a dense, cloud-filled atmosphere, oceans of liquid hydrogen and methane, and a complex weather system. These molecules recombine to form a variety of organic chemicals (substances that contain carbon and hydrogen), often including nitrogen, oxygen, and other elements essential to life on Earth. If Titan has life, it will not be as we understand it, or, in Starterk speak, "not as we know it". Other moons include Dione, Enceladus, Epimetheus, Prometheus, Mimas, Rhea, Janus, Tethys, etc. The seven satellites then known were named after Titans, Titanesses, and Giants—brothers and sisters of Cronus.

The planet Uranus has a Greek name; the Roman equivalent is Caelus. Uranus's five largest moons are Miranda, Ariel, Umbriel, Titania, and Oberon. They are named after characters in Shakespeare's plays, not mythological figures. Miranda is from The Tempest and is Prospero's daughter. Also, Ariel is not human on the magical Island; he is a spirit and a native of the Island where the drama is set. A more malicious figure than Ariel is Umbriel. From "A Midsummer Night's Dream". Titania is the queen of the fairies, and Oberon is the King of the Fairies and her husband.

The story of Neptune is one of scientific discovery: astronomers noticed an abnormality in Uranus's orbit and postulated that another planet was causing it, which they later identified as Neptune. By 1845, Uranus had completed nearly one full revolution around the Sun and astronomers Urbain Jean-Joseph Le Verrier in Paris and John Couch Adams in Cambridge, England, independently calculated the location of this postulated planet. Neptune, the Roman god of the sea, controlled winds and storms. Its Greek name is Poseidon. Neptune's atmosphere consists mainly of hydrogen and helium, with traces of hydrocarbons and possibly nitrogen. Still, it contains more ice, such as water, ammonia and methane, giving it a bluish colour. The moons are named Naiad, Thalassa, Despina, Galatea, Larissa, Hippocamp, Proteus, Triton, Nereid, Halimede, Sao, Laomedeia, Psamathe, Neso, etc. A naiad is a nymph in Greek mythology. Thalassa is the Greek goddess of the sea. Despina was a demigod, the daughter of Poseidon.

Another aspect I should mention is the search for Vulcan, a theorised planet some pre-20th-century astronomers thought orbited between Mercury and the Sun. Speculation about intermercurial bodies or planets, and even purported observations, dates back to the early 17th Century, after astronomers discovered Neptune from aberrations in Uranus's orbit. Astronomers thought aberrations in Mercury's orbit were caused by another planet. In 1915, Einstein's theory of relativity, an approach to understanding gravity entirely different from classical mechanics, removed the need for Le Verrier's planet. It showed that Mercury's orbital peculiarities resulted from the curvature of spacetime caused by the Sun's mass, not a new planet. At least I forget, in mythology, Vulcan was the Roman god of fire and the forge, and the mythical inventor of smithing and metalworking. His Greek equivalent is Hephaestus.

Pluto was named after the Greek god of the Underworld, and its moons are named Charon, Styx, Nix, Kerberos, and Hydra. Astronomers demoted Pluto from a planet to a dwarf planet after discovering much larger bodies in the Kuiper Belt. The Kuiper Belt is much like the Asteroid Belt, but most objects there are frozen methane, ammonia, and water instead of rocks. So the IAU had to set criteria for what makes a planet, and it came up with three.

1. It orbits the Sun.
2. It has enough mass to be in hydrostatic equilibrium (a nearly round shape).
3. It has "cleared the neighbourhood" around its orbit.

Another dwarf planet is also in the Kuiper Belt. Makemake comes from Rapa Nui mythology on Easter Island; it is the creator of humanity, the god of fertility, and the chief god of the "Tangata manu", or bird-man.

Much more was learned about the solar system from Voyager 1 and 2. The Voyager 1 and 2 probes delivered the first detailed views of the solar system's four giant planets and their large, shockingly diverse moons. Voyager 2 lifted off from Cape Canaveral, Florida, on 20 August 1977, with Voyager 1 following 16 days later. The Voyager probes launched to study the planets, but they discovered the wonders of the solar system's moons. They found Jupiter's turbulent atmosphere, Saturn's morphing rings, Uranus's tilted axis, and Neptune's Great Dark Spot, among other things. The concept of the Grand Tour began in 1964, when scientists noted that an alignment of Jupiter, Saturn, Uranus, and Neptune in the late 1970s would let a single spacecraft visit all outer planets using gravity assists. The particular alignment occurs once every 175 years. A gravity assist lets a spacecraft use a planet's gravity to gain speed and momentum, saving time and fuel.

Since other nations are going to space, Indian, Chinese, and Hawaiian names are now used to name bodies in our solar system. For example, Makemake is a dwarf planet in the Kuiper Belt. So you can see how fascinating astronomy can be. This is just the tip of the iceberg of what we know about our Solar System. I hope this sparks your interest.