Titania and Oberon
January 11, 1787: William Herschel looks into the night sky – again. Herschel was a German born British astronomer and composer. He was born in Hanover in 1738 and moved to England at the age of nineteen. He became interested in astronomy in 1773 and built his first large telescope in 1774. Already in his thirties, he spent the next nine years carrying out sky surveys in the hope of investigating double stars. He found that nebulae in the Messier catalog were instead, clusters of stars. As he continued his study of the sky, he found something that was not a star on March 13, 1871. He found a new planet, the first discovered since antiquity. He became famous overnight as a result. Uranus was now a part of the solar system.
On this day, Herschel found the first two moons of Uranus, Titania and Oberon. Other telescopes of the time were inadequate and the moons were not seen. As time went on, better instruments along with a better position of Uranus in the night sky led to more moon discoveries. William Lassell found Ariel and Umbriel in 1851. Nearly a century later, Gerard Kuiper discovered the last of the five spherical moons, Miranda. Uranus has a total of 27 known moons, all named after William Shakespeare or Alexander Pope characters. The five listed moons are all large enough to be dwarf planets if they circled the sun rather than the gas giant.
Titania, also called Uranus III, is about equal quantity of ice and rock. It is probably configured with a rocky core and an icy mantle. A liquid layer may reside between the two layers. The surface is relatively dark and is slightly red in color. It has evidence of many impacts with craters reaching up to 203 miles in diameter. The moon is about 980 miles in diameter at the equator. Between 2001 and 2005, infrared spectroscopy showed both water ice and frozen carbon dioxide present. The moon has only been studied once when Voyager 2 passed the system in January 1986.
Oberon, also called Uranus IV, is the second largest Uranian moon and the ninth most massive moon in the solar system. It is most likely that the moon was formed from the accretion disk which surrounded the planet just after it was formed. It seems to have the same basic structure as Titania. Oberon is only slightly smaller than Titania and measure about 946 miles in diameter at the equator. Ganymede (Jupiter) is the largest moon in the system and it and Titan (Saturn) are both larger than Mercury. Callisto, Io, Europa are the other three Jupiter moons larger than those surrounding Uranus. Our own moon is also larger as is Triton of Neptune. Pluto and Eris, two named dwarf planets, are also larger than both Uranean moons. Rhea (Saturn) is smaller than Titania but larger than Oberon.
All human discoveries seem to be made only for the purpose of confirming more strongly the truths come from on high, and contained in the sacred writings. – William Herschel
The undevout astronomer must be mad. – William Herschel
I was born on January 8, 1942, exactly three hundred years after the death of Galileo. I estimate, however, that about two hundred thousand other babies were also born that day. I don’t know whether any of them was later interested in astronomy. – Stephen Hawking
Astronomy’s much more fun when you’re not an astronomer. – Brian May
Also on this day: You Betcha – In 1569, the first state sponsored lottery is held at St. Paul’s Cathedral in London.
Kingsland – In 1917, an explosion at a munitions factory took place.
US Marshals – In 1794, the first US Marshal was killed in the line of duty.
Insulin – In 1922, a new treatment for diabetes was first used.
Commuted – In 2003, Illinois governor commuted 167 death row prisoners’ sentences to life without parole.