Flashback Friday: Uranus & Pluto

Posted on March 13, 2020 Updated on March 14, 2020

It’s Friday the 13th! Eek! Everybody…RUN! Hide! Yeah, well, enough of the hysteria. We have plenty of that going on with the corona beer virus. Sugar, rice, pasta, Clorox & Lysol hand wipes, bleach, hand sanitizer and toilet paper doesn’t stand a chance. Now, we have to deal with the dreaded number 13. E-gads! The humanity!

March 13 has been a rather busy day in history. Curiously, Uranus and Pluto are involved.

Uranus is the seventh planet from the sun. The name of Uranus references the ancient Greek deity of the sky Uranus, the father of Cronus (Saturn) and grandfather of Zeus (Jupiter) […]. It has the third-largest planetary radius and fourth-largest planetary mass in [our] solar system and, […] is the only planet whose name is derived directly from a figure of Greek mythology. Uranus is similar in composition to Neptune and, both have bulk chemical compositions which differ from that of the larger gas giants Jupiter and Saturn. Uranus’ atmosphere is similar to Jupiter’s and Saturn’s in its primary composition of hydrogen and helium but, it contains more “ices” such as water, ammonia and methane […]. It has the coldest planetary atmosphere in the solar system […]. Like the other giant planets, Uranus has a ring system, a magnetosphere and numerous moons. The Uranian system has a unique configuration because its axis of rotation is tilted sideways, nearly into the plane of its solar orbit. Its north and south poles, therefore, lie where most other planets have their equators. Voyager 2 remains the only spacecraft to visit the planet.

Like the classical planets, Uranus is visible to the naked eye but, it was never recognised as a planet by ancient observers because of its dimness and slow orbit. [Two hundred, thirty-nine years ago, today], Sir William Herschel first observed Uranus on March 13, 1781 (from the garden of his house at 19 New King Street in Bath, Somerset, England, now the Herschel Museum of Astronomy), leading to its discovery as a planet, expanding the known boundaries of the solar system for the first time in history and making Uranus the first planet classified as such with the aid of a telescope.

Pluto is an icy dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It was the first Kuiper belt object to be discovered and is the largest known dwarf planet. Pluto was discovered by Clyde Tombaugh in 1930 as the ninth planet from the Sun. After 1992, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt. In 2005, Eris, a dwarf planet in the scattered disc which is 27% more massive than Pluto, was discovered. This led the International Astronomical Union (IAU) to define the term “planet”, formally, in 2006, during their 26th General Assembly. That definition excluded Pluto and reclassified it as a dwarf planet.

It is the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but, is less massive than Eris. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and, is relatively small…about one-sixth the mass of the Moon and one-third its volume. It has a moderately eccentric and inclined orbit […]. This means that Pluto periodically comes closer to the Sun than Neptune but, a stable orbital resonance with Neptune prevents them from colliding.

[Observations] of Neptune in the late 19th century led astronomers to speculate that Uranus’s orbit was being disturbed by another planet besides Neptune. In 1906, Percival Lowell, a wealthy Bostonian who had founded [the] Lowell Observatory in Flagstaff, Arizona, in 1894, started an extensive project in search of a possible ninth planet, which he termed “Planet X“. Lowell and his observatory conducted his search until his death in 1916 but, to no avail. Unknown to Lowell, his surveys had captured two faint images of Pluto on March 19 and April 7, 1915 but, they were not recognized for what they were.

Percival’s widow, Constance Lowell, entered into a ten-year legal battle with the Lowell Observatory over her husband’s legacy and the search for Planet X did not resume until 1929. [23-year-old] Clyde Tombaugh, who had just arrived at the observatory, discovered a possible moving object on photographic plates on February 18, 1930. After the observatory obtained further confirmatory photographs, news of the discovery was telegraphed to the Harvard College Observatory ninety years ago, today, on March 13, 1930. Pluto has yet to complete a full orbit of the Sun since its discovery, as one Plutonian year is 247.68 years long.

The discovery made headlines around the globe. Lowell Observatory, which had the right to name the new object, received more than 1,000 suggestions from all over the world, ranging from Atlas to Zymal. Constance Lowell proposed Zeus, then Percival and finally Constance. These suggestions were disregarded. The name Pluto, after the god of the underworld, was proposed by Venetia Burney (1918–2009), an eleven-year-old schoolgirl in Oxford, England, who was interested in classical mythology.

Additional Reading:
Voyager 2 in the Uranium System (Zenodo site)
Uranus (NASA site)
Uranus (MIRA site)
Bath Preservation Trust
Eleven Awesome Facts About Pluto (geek.com)