In honor of the 240th anniversary of the discovery of Uranus, we decided to take a look at the discovery and what it meant for science. Although there is a strong case to be made for humanity to return to Uranus and continue to explore it, the discovery of Uranus also has an interesting story to tell. What makes the discovery of Uranus unique was that it changed how astronomers discovered planets as Uranus was the 1st planet in our solar system not discovered by visible eyesight.

Before being discovered by Sir William Hershel, the planet we now consider Uranus was seen by several people, but each observer considered it a star. The earliest known observation that was recorded and has survived until today was by Hipparchos, who in 128 BC might have recorded Uranus as a star for his star catalogue. This star catalogue by Hipparchos was later utilized and incorporated into Ptolemy’s Almagest.^[1] The earliest definite sighting was in 1690, when John Flamsteed observed it at least six times, cataloguing it as 34 Tauri. The French astronomer Pierre Charles Le Monnier observed Uranus at least twelve times between 1750 and 1769, including on four consecutive nights. [2]

However, the discovery of Uranus as a planet would not occur until 1781 by Sir William Hershel who on March 13th 1781 initially reported Uranus as a comet. Observing from the garden of his house Bath, England, Sir William Hershel was trying to find double stars in the Gemini constellation. when he thought was a comet. After reporting his weird discovery after a few days of observation, Herschel continued to think that this new object was a comet. However, upon sharing the data with other astronomers such as Finnish-Swedish astronomer Anders Johan Lexell, astronomers were able to determine that object. was indeed a planet. This was done by Lexell who was working in Russia, became the first person to compute the orbit of the new object, which had a nearly circular orbit around the sun. [3] This nearly circular orbit around the sun led Lexell to the conclusion that this new object was a planet, rather than a comet. Upon seeing the data, Herschel became convinced as well and had the task of naming the new planet, which is a story for another time.

Importance Of Discovery

The importance of the discovery of Uranus could not be understated. Before its discovery, astronomers did not consider the potential for additional planets in the solar system. However, after Uranus was discovered, astronomers around the world became interested in learning more about the planets in the solar system. By taking the time to plot the rotation of Uranus around the sun, astronomers were then able to determine that there was an object orbiting the sun that was affecting the orbit of Uranus. Although not found until September 23rd, 1846, the location of the planet now named Neptune provided astronomers an opportunity to learn more about planets orbiting stars like our sun. When Johann Gottfried Galle discovered Neptune, the planet was nearly located at the position predicted by French astronomer Urbain Le Verrier.[4] This meant that by studying and refining mathematical equations for the orbit of these outer planets in the solar system, astronomers were able to study planets in a way never before possible.

The chance discovery of Uranus, Neptune, and then Pluto helped scientists create and refine the mathematics that modern astronomy uses and relies upon to detect exoplanets that orbit suns in other solar systems. Building and utilizing the work from previous astronomers, scientists and astronomers have developed a plethora of methods and modern telescopes to detect planets in other solar systems. The discovery of exoplanets is its own discussion, but if humanity is to one day colonized other galaxies and stars, finding habitable planets will be crucial. If humanity does ever colonize other planets in the outer solar system or in other solar systems, the interest in Uranus, Neptune, and Pluto would be crucial to that process. Regardless if humanity ever does travel to other planets and other star systems, this discovery of Uranus meant that scientists could find another object in the sky, other planets with their telescopes.

Sources And Further Reading

[1] =  René Bourtembourg (2013). “Was Uranus Observed by Hipparchos?”. Journal for the History of Astronomy. 44 (4): 377–387. Bibcode:2013JHA….44..377B. doi:10.1177/002182861304400401

[2] = Dunkerson, Duane. “Uranus – About Saying, Finding, and Describing It”. thespaceguy.com. Archived from the original on 17 April 2003. Retrieved 17 April 2007.

[3] = Johann Elert Bode, Berliner Astronomisches Jahrbuch, p. 210, 1781, quoted in Miner, p. 11.

[4] = O’Connor, J J. & Robertson, E. F. (1996). “Mathematical discovery of planets”