The Planet Uranus

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Podcast Transcript

Located approximately 1.8 billion miles or 2.9 billion kilometers from the sun, 19 times the distance from the Earth to the sun, is the seventh planet in the solar system, Uranus……or Uranus. 

Uranus is unlike any other planet in the solar system in several important ways, and its discovery was unlike the discovery of any planet up until that point. 

Since its discovery, our understanding of the planet has increased by leaps and bounds, and we are still learning more about it today.

Learn more about Uranus, what it is, and how it was discovered on this episode of Everything Everywhere Daily.

I might as well address the elephant in the room. The first thing that all of you probably thought of when you saw the title of this episode. 

How do you pronounce the name of the seventh planet from the sun? 

This is probably the overwhelming most popular issue when the subject of the planet comes up in popular culture. 

If you poll astronomers, they will almost universally tell you that the name of the seventh planet is URAN-us. Likewise, if you check various dictionaries and pronunciation guides, they will also confirm that URAN-us is how the planet is pronounced.

Therefore, for the remainder of this episode, that is what I will be calling it, even though I know many of you probably pronounce it…..ur-ANUS. 

The ur-ANUS pronunciation, of course, generates tons of giggles and puns. I will be addressing the history of the pronunciation later in the episode, but as for the rest of this episode, rest assured, I will not be talking about the rings around ur-ANUS or sending probes to ur-ANUS. 

So, with that…….

The planet Uranus was the first planet discovered that was not one of the original seven planets known to antiquity: the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn. You might be saying that some of those ancient planets aren’t, in fact, planets, and you’d be right, but you’d have to take that up with the ancients. 

Contrary to popular belief, the planet Uranus is visible to the naked eye. The problem is it is so dim and moves so slowly that ancient people never recognized it as a planet. To see it, you’d have to know exactly where it is.

Uranus was probably observed many times by people who simply didn’t know it was a planet. 

The earliest recorded observation may have been by the Greek astronomer Hipparchus, who may have put it in his star catalog in the year 128 BC.

The English astronomer John Flamsteed documented it in 1690 and called the star 34 Tauri.

The French astronomer Pierre Charles Le Monnier recorded at least twelve observations of Uranus between 1750 and 1769. 

Despite these early observations, the person who is credited with the discovery of Uranus is Sir William Herschel. On March 13, 1781, he made observations with his homemade six-inch reflecting telescope.  On March 17, he looked for it again and found, to his surprise, that it had moved. 

He assumed that he had discovered a comet, which is what he announced to the Royal Society on April 26.

However, in his report to the Royal Society, he indicated that as he changed the power of his telescope, the diameter of the object increased, which is something that planets do but stars do not.

Other astronomers, when given the coordinates of the object, reported similar odd findings. The British Astronomer Royal wrote back to Herschel after viewing it, “I don’t know what to call it. It is as likely to be a regular planet moving in an orbit nearly circular to the sun as a Comet moving in a very eccentric ellipsis. I have not yet seen any coma or tail to it.”

The Finnish-Swedish astronomer Anders Johan Lexell was the first person to compute the orbit of the object, and he concluded that the orbit was so circular it behaved more like a planet than anything else. The orbit was calculated to be about 84 years. 

The astronomy community quickly came to a consensus that what Herschel had discovered was indeed a planet, and by 1783, Herschel himself acknowledged it as such. 

As the discoverer of the planet, Herschel was given the right to name it. He decided to call it Georgium Sidus in Latin or George’s Star in English, named after the British King George III.

Here, I should note that Herschel was knighted and received an annual stipend from the king.

Needless to say, that name didn’t stick. No one outside of Britain wanted to name one of the plants after a foreign monarch. 

Many different names were proposed for the planet, including Neptune, Minerva, and Austräa. 

It was eventually the German astronomer Johann Elert Bode who proposed the planet should be named after a god from Roman mythology just to stick to convention. 

He proposed naming the planet after the Roman god of the sky OO-ranus. The Roman god, like pretty much every Roman god, was taken from the Greek god Ouranos (Ow-ran-os).  

He felt it also fit the theme because just as Saturn was the father of Jupiter, so too was Uranus, the father of Saturn.

Fun fact: Bode actually got his Roman gods wrong. Uranus is the Latinized name for the Greek god Ouranos, but the Roman god of the sky was actually Caelus, also stolen from the Greek but given a totally different name.

Early English dictionaries had the word pronounced as you-ran-us, as in, “you ran us over with your car.”

Once the existence of Uranus had been established as fact, other than its orbit, we still didn’t really know much about it. 

While the orbit of Uranus was calculated early on, over time, it became apparent that there was something wrong. The observed orbit of Uranus was different from the calculated orbit. In the mid-19th century, it was proposed that there was another planet that was causing the deviations in its orbit, and this eventually led to the discovery of Neptune. 

Even as telescopes got better, the images they could get of Uranus were never good enough to make detailed observations. For example, the length of the day on Uranus was estimated to be anywhere from 24 to 13 hours, which is an enormous discrepancy. 

Some moons had been discovered as early as 1787, and in 1977, some very faint rings were found as well. However, that was about it. 

The solution to the problem was to send a probe to Uranus to observe it directly. A golden opportunity to do this occurred in the 1970s and 80s. The planets were in such an alignment that it was possible to send a probe to visit all of the outer planets in a single trip, which became known as the “Grand Tour.”

The probe which was scheduled to visit Jupiter, Saturn, Uranus, and Neptune was Voyager 2. Launched on August 20, 1977, it would fly by Uranus and take pictures and measurements before being flung by gravity to Neptune and out of the solar system.

It took eight and a half years, but on January 24, 1986, Voyager 2 had its closest encounter with Uranus, coming within 81,500 kilometers, or 50,600 miles, from the planet. 

Side note: it was around the time of the flyby that the accepted pronunciation of the planet changed from ur-ANUS, to URAN-us. Mainly because astronomers and television hosts didn’t want to be subject to weeks’ worth of childish jokes as they reported on the flyby. 

As of this recording, this has been the only probe ever sent to Uranus. 

We learned an enormous amount from this very brief flyby and from subsequent observations made from advanced platforms such as the Hubble and James Webb Space Space Telescopes.

For starters, Voyager 2 confirmed the existence of rings around the planet, which had only been detected previously because they eclipsed background stars. 

Uranus has 13 known rings, which can be observed, although they are not as pronounced as the rings that are around Saturn. 

There are 27 known moons of Uranus. The names of the moons come from the names of characters by the English authors William Shakespeare and Alexander Pope. 

The largest moons are Miranda, Ariel, Umbriel, Titania, and Oberon.  The largest moon, Titania, has a diameter of 1576 kilometers, or 980 miles. Its surface area would be about the same size as Australia.

The atmosphere of Uranus mostly consists of hydrogen and helium, but what sets it apart from Jupiter and Saturn is the large amount of methane in the atmosphere, which is the third most abundant age. 

The differences in the atmosphere led to Uranus and Neptune being classified as “ice giants” instead of “gas giants” like Jupiter and Saturn.

The winds on Uranus are believed to approach speeds of 900 km/h or 560 mph. 

However, none of these facts are what make Uranus really interesting. The really interesting thing about Uranus is its rotational axis. 

Almost everything in the solar system, the sun, plants, and moon, roughly have a similar axis such that the north and south poles are perpendicular to the orbital plane. It might tilt a bit one way or the other, but this is generally true.

Uranus, on the other hand, has an axis that is tilted 97 degrees. That means that one of the poles can face directly at the sun. The rotation of the planet around its axis is quite fast at seventeen and a quarter hours. However, because of the extreme tilt of the axis, a day on Uranus doesn’t equate to a light and dark cycle. 

Rather, day and night are the equivalent of season. One pole is exposed to the sun for 42 years, while the other pole is in darkness.  

On top of the odd axial tilt of the planet, nine of Uranus’ moons orbit in a retrograde motion, opposite to the rotation of the planet and opposite to how the other 18 moons orbit the planet. 

Uranus has a magnetic field, which was completely unknown until the Voyager 2 flyby. This is not uncommon on a planet. However, Uranus again has to be difficult because its magnetic field isn’t aligned with its poles. 

The magnetic poles of Uranus are located 59 degrees off the axis of the planet. 

So, what causes this weird behavior in its axis, its moons, and its magnetic field? 

The best theory right now is that several billion years ago, Uranus collided with a large, Earth-sized object, which caused the entire planet to tip on its side. 

While we have learned a lot about Uranus since the Voyager 2 flyby, there is still a lot we don’t know. 

There have been several proposals for another mission to Uranus, but as of right now, nothing has been approved. 

One of the reasons for the lack of activity in Uranus exploration is because of how difficult it is to reach the planet. When Voyage 2 was launched, it could use gravitational assists from Jupiter and Saturn to get there in a relatively quick nine years. 

Today, those gravitational slingshots aren’t available, and anything launched today wouldn’t reach the planet for another 18 years. In 2022, NASA’s Planetary Science Decadal Survey put a future mission to Uranus high on the priority list. There is nothing approved as of yet, but the next best launch windows would be in 2030 and 2034. 

Hopefully, sometime in the next decade, a probe will be launched that will not just fly by Uranus but will actually go into orbit for an extended period of observation. 

Until then, even if we can turn our best telescopes to the planet, Uranus will remain one of the oddest and most mysterious places in the solar system.