Today is the birthday of German Philosopher Immanuel Kant, born April 22, 1724, who was the first person to suggest that nebulae were galaxies or ‘island universes’ at incredible distances.  A contemporary of the French Astronomer Charles Messier, Kant made this assertion while Messier was compiling his famous ‘catalog’ of celestial objects that were clearly neither stars nor comets, which is what Messier was searching for.  But when the word nebula originally entered English in the early 15th century, it had nothing to do with astronomy.  Arriving as nebule meaning a cloud or mist from the Latin word nebula meaning mist, which in turn came from the Proto Indo-European root word *nebh-meaning cloud, vapor, fog, moist, sky.  Ancient Greek had the related word nephele, nephos which also meant cloud. When the word nebula reappeared in English it had a medical meaning for cataracts or cloudy defects in the eye.  The astronomical meaning of a cloud-like patch in the night sky was first recorded around 1730. It wasn’t until the early 20th century with the advent of modern and powerful telescopes that nebula were fully understood as massive clouds of gas and dust.  

Image of the Ring Nebula, courtesy NASA from Hubble Space Telescope Program.  

On March 25, 1655 Dutch astronomer Christian Huygens discovered the first moon of Saturn, later named Titan.  Huygens did it with the help of his brother Constantijn, also an astronomer, with a telescope they built themselves.  

Huygens called it Saturni Luna, Latin for Saturn’s Moon in his publication of the discovery, New Observations of Saturn’s Moon.  When the next five moons of Saturn were discovered a few decades later, astronomers began referring to them by number, Saturn I through Saturn VI, though the list was not sequential and Titan was variously named Saturn I, IV and even VI.  The name Titan was given 50 years after Huygen’s death by astronomer John Herschel, son of Anglo-German astronomer William Herschel in John Herschel’s 1857 publication  Results of Astronomical Observations Made at the Cape of Good Hope.  He named the moons after the twelve titans (Τῑτάν), the mythical race of deities that preceded the traditional canon of Greek deities.  

The word titan was in common use in English by the 1500s, becoming an adjective by 1709, then applied to the element titanium in 1796 and finally the moon of Saturn.   

Image of Titan from the Cassini program, courtesy NASA

Although scientists as early as Aristarchus of Samos knew the relationship between the sun and earth around 270 BCE, it wasn’t until 1543 that Nicholas Copernicus published his masterwork De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), published the same year that he died that the heliocentric model received wide distribution. Perhaps his death and inability to defend his thesis led to the very slow spread and adoption of his idea, so that by the year 1616 a group of cardinals and bishops under the direction of the Vatican met to denounce Galileo Galilei, who was using the results of his observations made with the new technology of the telescope to re-introduce the heliocentric model of the solar system. A decade and half passed before Galileo was dangerous enough to draw a trial, which commenced on this day in 1633. Galileo was furious with the philosophers, theologians and scientists who denounced his idea, complaining to his friend and fellow astronomer Johannes Kepler,

My dear Kepler, I wish that we might laugh at the remarkable stupidity of the common herd. What do you have to say about the principal philosophers of this academy who are filled with the stubbornness of an asp and do not want to look at either the planets, the moon or the telescope, even though I have freely and deliberately offered them the opportunity a thousand times? Truly, just as the asp stops its ears, so do these philosophers shut their eyes to the light of truth.

He lost the trial and spent his last eight years under house arrest, working on his theories from his home in Pisa.

The word heliocentric comes from Ancient Greek, a combination of the words ἥλιος (helios) meaning sun and κέντρον (kentron) meaning center. It would take another three centuries for scientists to understand that not only is the Earth not the center of the Universe, neither is the Sun.

Image from Copernicus in the public domain.

This blog has been dedicated for over a year to telling the stories of words and word origins in science. Science (along with math, technology and engineering) is a rich field for etymologists, as the discoveries of science and the creation of new words almost always have a great back story to go with the word.

Today, however, is your chance to help create a science word, by naming the two newest moons of Pluto: currently known as P4 and P5. First the current names:

Pluto is the Roman name for the Greek god Hades, master of the underworld. The underworld was the place where the souls of the departed go after they die. After Clyde Tombaugh discovered Pluto from the Lowell Observatory in 1930, a little girl named Venetia Burney from Oxford, England suggested that he name it “Pluto”. Tombaugh liked the idea, in part because the initial letters “PL” reminded him of Percival Lowell, namesake for the obsevatory and the first to propose the existence of a “Planet X”.

Charon is the name of Pluto’s largest and innermost moon. It was discovered in 1978 by James Christy. In mythology, Charon was the boatsman who ferried the souls of the dead across the river Styx into the underworld.

Nix and Hydra are the names of Pluto’s next two moons, discovered in 2005 in Hubble telescope images by a team of astronomers led by Hal Weaver and Alan Stern. Nix is the goddess of the night and Hydra is the name of the many-headed monster who guarded one of entrances to the underworld. These names, with initials “NH”, were chosen to match the initials of New Horizons, the NASA spacecraft now on its way to Pluto.

Here is a little bit of background on the names that currently appear on the ballot for the new moons:

Acheron: One of the five rivers of the underworld, symbolizing pain.

Alecto: One of the furies, hideous snake-haired monsters who were servants of Hades. It was the job of Alecto to punish mortals for their crimes of anger.

Cerberus/Kerberos: The three-headed dog who guards the gates to the underworld, preventing the the dead from escaping.

Erebus: A primordial god and the personification of darkness. With Nyx, he fathered many children including Hypnos and Styx.

Eurydice: The wife of Orpheus, for whom he entered the underworld. During their journey home, Orpheus violated his agreement with Persephone not to look back, and Eurydice was lost forever.

Heracles/Hercules: The heroic demigod who slew the Hydra, entered the underworld and who also carried Cerberus back. He is one of very few who ever returned from the underworld.

Hypnos: A son of Nyx and the personification of sleep.

Lethe: One of the five rivers of the underworld, symbolizing oblivion. It flows through the cave of Hypnos and merges with the river Styx.

Obol/Obolus: The coin paid to Charon in order to obtain passage across the river Styx.
Orpheus/Orfeus: A gifted musician who entered the underworld to retrieve his wife Eurydice. He charmed Hades and Persephone with his music, and became the only mortal ever to return from the underworld.

Persephone/Proserpina: A goddess kidnapped by Hades to become the queen of the underworld. She is the symbolizes vegetation and rebirth.

Styx: The river that separates Earth from the underworld. This name also refers to the goddess of the river Styx, daughter of Nyx and Erebus.

You can vote here: www.plutorocks.com

Special thanks to www.space.com and www.plutorocks.com for this content.

The Coalsack Nebula is a prominent asterism visible in the Southern Hemisphere, located in the Southern Cross constellation. It was known to ancient cultures, notably among the Australian aboriginal peoples who knew it as the Great Emu or the Emu in the Sky. It was first catalogued by Europeans in 1499 by Vicente Yañez Pinzon, the Spanish explorer, navigator and conquistador who sailed with Christopher Columbus in 1492 as the Captain of the Niña. It was also known as il Canopo fosco (the dark Canopus) by Amerigo Vespucci and later called Macula Magellani (Magellan’s Spot) or the Black Magellanic Cloud to distinguish it from the Magellanic Clouds in the Northern Hemisphere. The Pre-Columbian Incans knew it as Yutu which meant a partridge-like southern bird. It wasn’t until the 1970s that powerful telescopes were able to show that it actually had a faint glow, reflecting the surrounding light from the Milky Way Galaxy.

Image of the Coalsack Nebula courtesy naskies, used with permission under a Creative Commons 3.0 license.