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 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.
Happy Birthday Galileo Galilei, born February 15, 1564.
Painting of Galileo Facing the Roman Inquisition by Cristiano Banti, 1857, in the public domain.
Image from Copernicus in the public domain.
When is a planet not a planet? This question has troubled scientists and students for decades, and the recent demotion of Pluto from planet to plutoid marked a significant change in how scientists classify planets. In 2006 the International Astromical Union identified three key criteria to classify a body as a planet:
By this definition Pluto was excluded, but the discovery of a transneptunian object on January 5, 2005 added very briefly a planet to the solar system.
Many teams were racing to map the outer solar system, specifically the belt of asteroids and debris in the scattered disc known as transneptunian objects, and the discovery of Eris and Dysnomia took several years of searching, two years of analysis with both computers and good old fashioned legwork. The team of Mike Brown, Chad Trujillo, and David Rabinowitz had programmed their computers to rule out objects moving too slowly to count and missed seeing Eris when it was first photographed. Manually pouring over the photos almost a year and a half later, they found the largest (to date) plutoid or dwarf planet.
Wanting to name more sky objects after women, internally the team referred to the dwarf planet as Xena, after the popular television series. After a period of several years (and much consensus building) the name Eris was settled on. Eris was the goddess of strife in Greek mythology, the meddling troublemaker who doomed the marriage of Peleus and Thetis, the parents of Achilles, which led to the disastrous war that destroyed both Troy and much of the invading Greek armies. Eris’s own son was named Dysnomia, meaning lawlessness, and when the Hubble Space Telescope discovered that Eris had a moon, well, the name was inevitable. Since the discovery of Eris and Dysnomia, several more plutoids have been discovered, but none yet as large. Eris was considered a planet for less than a year, before both Eris and Pluto were reclassified as plutoids.
Images of Eris and Dysnomia courtesy NASA/Hubble.
All the romance and credit go to Apollo XI and Armstrong, Aldrin and Collins, but please don’t forget Apollo 8 and the amazing contribution made by these Astronauts: Commander Frank Borman, Command Module Pilot James Lovell, and Lunar Module Pilot William Anders, who circled the Moon ten times exactly 45 years ago today on Christmas Eve 1968.
Do not underestimate the technical achievement or ambition of Apollo 8: the mission had originally been scheduled as an Earth orbit only mission for early 1969 but was bumped up in the schedule and re-designed to travel to the moon months earlier as the Lunar Module was not ready for flight. Apollo 8 took three days to travel to the Moon, then spent 20 hours making 10 orbits, taking the famous ‘Earthrise’ photo on its fourth orbit, after Borman turned the craft to face the lunar surface. Apollo 8 would return safely to Earth for splash down on December 27, 1968. Lovell would later fly the near disastrous Apollo 13 mission, while Borman and Anders were on their last flight. Go out tonight and pause to remember these three men, travelling over half a million miles to take a photo-a photo that re-defined the way we look at the Earth.
The Earth’s moon holds a special place in the human heart: it exists not only as our nearest celestial neighbor, it is also one of the richest sources of metaphor and poetry. Despite Shakespeare’s denigration that “the moon's an arrant thief, And her pale fire she snatches from the sun,” the moonhas a long history in literature, poetry and song. The word itself comes from Old English mona, from Proto Germanic *mænon- (cf. Old Saxon, Old High German mano, Old Frisian mona, Old Norse mani, Dutch maan, German Mond, Gothic mena all meaning moon), from Proto Indo European *me(n)ses- meaning moon, month (cf. Sanskrit. masah meaning moon, month; Avestan ma, Persian. mah, Armenian mis month; Ancient Greek. mene moon, men month; L. mensis “month;” O.C.S. meseci, Lith. menesis meaning moon, month; Old Irish mi, Welsh mis, Breton miz month), probably from base *me- meaning to measure, in reference to the moon's phases as the measure of time. In Greek, Italic, Celtic, Armenian the cognate words now mean only month. First used to describe the satellites of other planet’s 1665.
Shakespeare quote from Timon of Athens.
All Images courtesy NASA in the public domain. Earthrise photo by William Anders.
The first day of winter and the shortest day of the year begin later today, the day of the winter solstice. At 5:11 pm Greenwich Mean time, the Solstice will arrive. The word solstice is relatively old in English, dating back to the 13th century. Solstice derives from the Latin word solstitium meaning very literally the point at which the sun stands still, a combination of the words sol meaning sun and the past participial stem of sistere meaning to come to a stop, make stand still. Celebrated thoughout history as either a secular or religious day, the solsticemarks the point on the ecliptic when the Northern Hemisphere is pointed most away from the sun and therefore has the shortest day.
The first planetary nebula discovered was the Dumbbell Nebula or Apple Core nebula and was discovered by Charles Messier in 1764. Approximately 1400 light years from earth, the Dumbbell Nebula has several distinguishing features: the white dwarf at the center is considered the largest known white dwarf at the center of a nebula at a radius of 0.055 ± 0.02 R☉.
When Messier found the nebula in the constellation Vulpecula, the constellation was only a century old, named by Polish astronomer Hevelius in 1687 Of the name Vulpecula, Hevelius said this:
Messier composed his famous catalog while comet hunting-he created a list of asterisms that were neither comets nor stars to keep track of them as he searched for comets. The term planetary nebula came from German Astronomer William Herschel in the 1780s who though he was seeing planets forming, though they are formed of ionized gas expanding out from old red giants late in their lives.
When the word nebula 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.
Yes, that gorgeous ringed planet with the satellites out of Shakespeare is Uranus and not Saturn. Today is the birthday of William Herschel (15 November 1738 – 25 August 1822) a German born British astronomer known today as the discoverer of the planet Uranus in March of 1781. He also discovered two of Uranus's moons, Titania and Oberon and two moons of Saturn.
He is also credited with the discovery of Infrared radiation, and to honor that the image above of Uranus is a 1998 false-colour near-infrared image of the planet showing cloud bands, rings, and moons obtained by the Hubble Space Telescope’s NICMOS camera.
Herschel named his discovery George, oddly enough, to commemorate his new patron, King George III. At the time he said this:
In the fabulous ages of ancient times the appellations of Mercury, Venus, Mars, Jupiter and Saturn were given to the Planets, as being the names of their principal heroes and divinities. In the present more philosophical era it would hardly be allowable to have recourse to the same method and call it Juno, Pallas, Apollo or Minerva, for a name to our new heavenly body. The first consideration of any particular event, or remarkable incident, seems to be its chronology: if in any future age it should be asked, when this last-found Planet was discovered? It would be a very satisfactory answer to say, ‘In the reign of King George the Third’.
Few astronomers outside of England liked the name, however, and astronomers began proposing alternatives almost immediately. German astronomer Johann Elert Bode called it Uranus (Ancient Greek: Οὐρανός) after the Ancient Greek god of the sky, the logic being that as Saturn was the father of Jupiter, the new planet should be the father of Saturn. It wasn’t until the middle of the next century that atlases dropped Herschel’s name and adopted Uranus. Learn all about William Herschel here:
All images in the public domain
The movie Gravity shows the terrifying drama of a major impact event on the International Space Station, but the daily danger faced by the ISS is both smaller and more common. You can clearly see the shields on the ISS (shown above under construction above New Zealand), known as Whipple Shields or Whipple bumpers. The Whipple shield is designed to protect both manned and unmanned spacecraft from hypervelocity (mostly) microscopic particles. Unlike the solid or monolithic shields on early spacecraft, the Whipple shield functions by having a thin shield that absorbs the initial impact and disperses the impact over a larger area thus reducing the force of the impact. With orbital debris travelling at speeds measured in miles per second, the shields play a critical role, as debris the size of a small ball bearing (see below) could be devastating.
The Whipple Shield is named for its designer American astronomer Fred Whipple, born November 5, 1906, died August 30, 2004. In addition to protecting spacecraft, Whipple designed a device for cutting tin foil into chaff to use to fool enemy radar, he came up with the ‘dirty snowball’ model of comet anatomy, discovered several comets and asteroids while working at the Harvard College Observatory for over 60 years. Happy Birthday, Fred!