The Discovery of Uranus and Why Is It Such an Oddity

Uranus was the first planet to be discovered since antiquity but it still continues to surprise us today. Here we take a closer look at the 'black sheep' of the Solar System.
Christopher McFadden

Uranus was thought to be a star for many years. It's the seventh planet in the solar system and with an average temperature of -217 degrees Celsius, it is the coldest of the lot.

Unlike its siblings, it rolls around the Sun rather than spins and was the first planet to be discovered since antiquity (or was it?). It has less gravity than Venus yet is able to wield a sizeably thick atmosphere and has no less than 27 known moons

Its atmosphere of helium, hydrogen, and methane envelope an icy mantle encasing a barely glowing iron core. It also has two sets of rings and its moons are named after Shakespearean and Alexander Pope characters.

In the following article, we'll take a look at the Solar System's 'oddball' and pay homage to its long and fascinating past. 

When Was the Planet Discovered and Named Uranus?

Uranus is the epitome of the age-old adage "hidden in plain sight". On a nice clear sky with very little light pollution, you can (if your eyes are strong enough) spot Uranus without binoculars or a telescope.

Of course, you will need to know exactly where to look and it's not very bright and pretty small. Despite this, if you have your timing right you might, just barely, spot it in the night's sky. 

You could, of course, cheat and use one of the many astronomical apps available to guide you. 

Yet despite this (excusing the app), Uranus wasn't officially noticed until as late as 1781!

It has long been known that even the Babylonians knew about all of the planets of our solar system between Mercury and Saturn in antiquity. 

Initially, Uranus's discoverer, Sir William Herschel, thought it was a comet, rather than a planet, and duly informed other prominent astronomers at the Royal Society.

discovery of Uranus
Source: Bruce Irving/Flickr

But his peers were confused. A comet is normally very bright and is usually noticed because it has come close to the sun. 

If this were true it should be moving a lot faster and have a tail - which this 'new' discovery didn't. It also appeared to have a circular orbit.

It must, therefore, be a planet.

William tried to name his new discovery Georgium Sidus (George's Star), in honor of King George III. A move that secured him a princely annual salary of £200 from the crown. 

Although popular in Britain, the international community was less than impressed. German astronomer, Johann Elert Bode, proposed the name Uranus in 1783 which was later widely adopted including by the British.

Herschel and Uranus funny
Source: NASA

Who Discovered and Named Uranus?

Although Herschell is widely acknowledged as the planet's discoverer, many other prominent astronomers acknowledged its existence long before William. 

Ancient records seem to indicate that a Greek astronomer, Hipparchus, noted the planet in the 2nd Century BC. However, he recorded it as a star, not a planet. You may have heard his name before - he was not only an astronomer but also the founder of trigonometry.

Hipparchus's work was later incorporated into Ptolemy's Almagest. This would become the main source for later Islamic astronomers and scholars for the next 1,000 years until the middle ages.

The next earliest and reliable discovery of the planet was made by English astronomer John Flamsteed in 1690. He, like Hipparchus also misidentified it as a star and cataloged it in the Taurus Constellation

During the middle of the 1700's French astronomer, Pierre Lemonnier made a further dozen sightings. He like his predecessors recorded it as another star. 

Then, finally, Sir William Herschel stepped up to the plate and on one fateful evening on the 13th March a 1781 (whilst looking for binary stars), he also 'found' Uranus. 

Initially recording it as a "Nebulus star or perhaps a comet" on the 26th April 1781 he later settled on a comet as it appeared to be moving. Excited by his discovery he duly reported it to the Royal Society, maintaining it was a comet but that it did have some similarities to planets. 

His discovery caused a storm in the astronomical community of the day with many concluding it was indeed a planet. Herschel was eventually persuaded in 1783

Sir William Herschel
Source: J. Boilly/Wikimedia Commons

Why Did They Call it Uranus?

Initially, Uranus was called something completely different. Sir William Herschel wanted to name it after his country's king, George III.

His proposal to call it Georgium Sidus ("George's Star") was popular in his homeland of Britain but was less well received in the international community - for obvious reasons.

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Once its true nature was confirmed, many believed it inappropriate to include an earthly king amongst gods in Greek and Roman mythology - as was the tradition.

And so, a German astronomer  Johann Elert Bode proposed the name Uranus in 1782. Uranus is the Latin form of Ouranos (God of the sky).

In fact, Uranus is the only of the major eight planets (not forgetting the recently downgraded Pluto) to be given the Greek version of the god's name - albeit Latinized. All others are the Roman forms - after all, it was the Romans who officially named the ones visible to the human eye at the time.

In the Romanized world at least. Technically speaking Uranus's Roman equivalent should actually be Caelus. So why was Uranus chosen?

Uranus color
Source: littleplanetfactory

It must be born in mind that Uranus was the first major planet to be found since antiquity. And so the only one without a name that hadn't already been accepted for thousands of years.

At this time Greek and Roman civilizations tended to be grouped together under the generic term "Classical Antiquity". It was not uncommon for most of the intelligentsia to look upon the Roman gods as Latinized forms of the Greek forerunners - which of course they are.

The other planets also followed a convention of naming the outer planets in order of generation. Mars (Ares) was the son of Jupiter, Jupiter (Zeus)  was the son of Saturn (Cronos) with Caelus/Ouranus/Uranus being the mythological father of Saturn. 

But wait, there is more.

Another reason for his choice of Uranus might be the fact that Caelus already had a celestial body named in his honor.

A quarter of a century early, Nicolas Louis de Lacaille identified a constellation that became known as Caelum Scalptorium.  

Whatever the reason, Bode's choice quickly became the most widely used outside of Britain and was officially adopted in 1850 in the UK when the HM Nautical Almanac Office dropped Georgium Sidus in favor of Uranus. 

Why Was Uranus Not Discovered Until 1781?

The short answer is it was, as we have seen. The long one, of course, is a lot more complex.

Before that fateful night, and nomenclature battle that followed, "Uranus" had been spotted and noted many times in history. The difference in 1781 was that it was eventually recognized as a planet, not a star or comet.

All the other major planets (apart from Neptune and traditionally Pluto) had already been named by the end of the Roman Empire. These planets are easily observed by the human eye without the use of a telescope or other device - unless you have superb visual acuity and know where to look, of course.

Although noted by Hipparchus and Ptolemy in ancient antiquity it would take thousands of years for it to be mentioned again. It took human technology time to catch up so that it would be, at least possible, to more easily find others. 

The first telescope wasn't developed until 1608 by Hans Lippershey, and it would gradually improve in power over the next four centuries. 

As the technology improved it enabled astronomers of "The Enlightenment" to make more detailed and scientific surveys of the cosmos. It was now only a matter of time before Uranus was "discovered".

Lippershey first telescope
Source: Numlx/Wikimedia Commons

Why Are Planets Named After Greek Gods?

Technically speaking, the planets are actually named after Roman and Greek gods - in the western world at least. The truth is that the five most easily observed planets (Mercury, Venus, Mars, Jupiter, and Saturn) were all given different names by different civilizations.

Interestingly, Earth is the odd one out. The English word Earth comes from old Germanic and English though it's not uncommon to call our beloved home Terra. It also has other names in different languages.

In Turkish, it is known as  dünya’ (doon-ya) and ‘aarde’ in Dutch, but we digress.

The Roman Empire was the largest in antiquity and it had an enormously influential effect on the European continent, nations, and cultures therein. Romanization was in effect for almost 700 years and would become the foundation of languages and culture for nation states that formed after the fall of Rome.

The adoption of Christianity by the Empire would further enforce this until the modern day. 

For this reason, Western Civilisation uses the Roman or Latin forms of Greek god's which were formalized by the Roman Empire during their reign. The Roman's named the planets according to their movements and appearances - though they believed them to be "wandering stars". 

And so, these names basically stuck in the European psyche. The names became the scientific standard during the "Age of Enlightenment" in Europe and are a tradition held today.

Which God Was Uranus?

Ouranus (Greek original) Caelus (Roman version of Ouranus) or Uranus (Latinised Ouranus) was the ancient god in Greek and Roman pantheon. He was one of the primal gods of Greek mythology and was symbolic of the sky or heavens. 

According to legend Uranus was the son of Gaea with conflicting stories explaining his father was either Chaos or Aether. 

Uranus and Gaea had many children (yes with her son) - the twelve Titans, three Cyclopses, and three Hecatoncheires. He was not a good father, however, and hated his offspring.

He banished his children to Tartarus deep inside Gaea who, unsurprisingly was not happy. She created a diamond sickle and instructed Cronos (Saturn to the Romans) to find and castrate his father in his sleep. 

His blood is then said to have fallen to Earth where it created the Eronnyesm the Giants and Meliads. His semen fell into the sea giving birth to Aphrodite. 

Uranus was no more and Cronos's rule began in earnest. 

When Were The Rings of Uranus Discovered?

With all the rigmarole of finding the planet in the first place, you might be forgiven for thinking that was the end of the story. But the story of Uranus didn't end in 1781.

For many centuries, it was believed that only Saturn had a set of beautiful and majestic rings. This assumption was smashed when in 1977 an astronomical team under James L. Elliot, Edward W. Dunham, and Douglas J. Mink first spotted them.

Today, we now know that there are in fact 10-13 distinct rings around the planet. They start at around a distance of 38,000 km (from the planet's center) and extend out to around 98,000 km

Unlike Uranus's bigger sibling Saturn (or is it son?), the rings of Neptune are relatively very dark and are composed of chunks of rock rather than dust and ice. Each measuring between 0.2 and 20 meters across. 

Which is Bigger Uranus or Earth?

Uranus is bigger than Earth, by a ratio of about 4:1

Earth's diameter is 12756 kilometers compared to Uranus that has a diameter of 51152 kilometers. Not only that, but Uranus has a total that is about 14.5 times that of our mother planet.

This is impressive given that Uranus, one of the gas giants, is mainly composed of helium, ice, ammonia and other gases. 

Uranus and Earth comparison
Source: sciencenetlinks

How did Uranus get its tilt?

Apart from its size, weight, distance from the sun and interesting history of discovery and name, there is one very unique feature of the planet - its peculiar tilt.

Its axial tilt is considerable at an angle of 98 degrees relative to the sun. For comparison, the Earth axial tilt is around 23.5 degrees (at least today).

This makes it very different indeed to its 'brothers and sisters' in the solar system. They are all ostensibly 'spinning tops' whereas Uranus can be more likened to a rolling ball. 

This makes for interesting solstices on the planet with one pole facing the Sun constantly. Because of this, there is only a very thin slice of the planet's surface that experiences anything like night and day on Earth.

Its orientation means the planet's poles receive about 20 years of constant sunshine and another of complete darkness. During equinoxes, the planets equator does face the sun and so experiences day/night cycles. 

But what is its tilt all about? What happened?

It was once thought that Uranus collided with another proto-planet early in its history. This sent Uranus into an uncontrollable tumble until it came to rest in its current axial tilt. 

Problem solved - actually no. There is a problem.

If this was true how is it that the moon's of Uranus also have the same tilt? Something was up. 

Current belief is that Uranus experienced a series of collisions - two to be precise.

What Is So Special About Uranus/ What Makes Uranus Unique?

The main characteristic of Uranus is its odd tilt that we discussed earlier, but there is more to this strange planet than that.

Here are some of the "Grandfather of the Gods" other unique qualities:-

 - Uranus is the coldest planet in the solar system - At 2.88 billion km from the Sun it's closer than Neptune but a lot colder with an average temperature of 72K. It can get as cold as 55K.

 - The planet rotates around its axis once every 17 hours and 14 minutes. It also does so in a retrograde direction compared to other planets (except Venus).

- Wind speeds on the planet can reach as much as 900 km per hour.

- Uranus also has the nickname of the "ice giant". Despite it being a gas giant its mantle is made of ice that encases a rock and iron core.

- The element Uranium was discovered in 1879 and was actually named after Uranus.

Uranus structure
Source: FrancescoA/Wikimedia Commons

Could There Be Life on Uranus?

As we learn more about the life we understand that it is very resilient indeed. On Earth, we find it in every place you conceive it.

You can find it encased in ice, in boiling water, deep on the oceans floor and areas of high radiation. So it might seem reasonable to wonder whether life exists in Uranus.

The problem is that Uranus is cold, very very cold. The closer you get to the iron core, the warmer it gets with the core itself a toasty 5000K.

But the ever-increasing crushing pressure likely cancels out any real benefits from the warmer surroundings the closer you get to the core. 

Uranus also lacks any real hard surfaces and is mostly made of ice, methane, water, and ammonia all enshrouded by a high-speed atmosphere of hydrogen and helium.

All life on Earth also requires energy from the Sun - this is in short supply on Uranus.

The planet also lacks other processes we take form granted here on Earth like volcanism that could prove an alternative source of energy for life.

Whilst you might be able to conceive of some form of life that could survive on the planet it would need to be very alien indeed to what we have on Earth. So much so we might not ever be able to recognize it as such.

Uranus alien dice
Source: Matěj Baťha/Wikimedia Commons

What Are The Seasons of Uranus Like?

Because of Uranus's peculiar tilt (98 degrees), it has very extreme seasons indeed. Each 'season' lasts roughly 20 years with incredibly extreme differences between them.

For half of its 'year' (roughly 40 Earth years), during the planets equinoxes, its equator faces the Sun - but you probably wouldn't enjoy a spring or autumn holiday there.

During summer and winter, the pole of the Uranus spends another quarter-year of its orbit facing the sun, ostensibly it's summer, and its winter in complete darkness (its winter). 

If it were possible to stand on Uranus's surface (you'd actually sink if you tried), you'd see a gradual rise of the Sun from the horizon. It would then circle higher and higher gradually sinking again plunging you into complete darkness for 42 years.

When the sun finally returns it's thought that wild storms might erupt as the decade's dormant atmosphere is suddenly 'bathed' in solar energy. During Autumn and Spring, things are a little more 'normal' with day and night cycles of 13 hours.

Uranus orbit

Why is Uranus Blue?

The Uranian atmosphere comprises a mixture of hydrogen, helium, and methane. The planet gets its interesting color from the way in which the methane component interacts with light from the Sun in the upper atmosphere.

When sunlight hits the atmosphere of the planet some of its reflected back out into space whilst other bits are absorbed by the gases that comprise it.

This gas absorbs EM light waves in the red part of the spectrum. This means that it reflects blue from the planet's atmosphere back out into space. For this reason, Uranus appears to be colored blue. 

Technically speaking, Uranus is actually more of blue-green color rather than just blue.

Why Is It So Cold on Uranus?

Uranus is effectively a cold dead ball of ice and gas. Its gaseous atmosphere is actually pretty thick which is surprising since Uranus's gravity is then than that of Venus.

For this reason, the only way the thick atmosphere can be held in place is because it is so cold on the planet. But why?

This is hotly debated but it likely the planet's odd tilt plays a major factor - after all, shouldn't it be warmer than Neptune?

Uranus is actually colder than Neptune besides being closer to the Sun. This must mean that Uranus loses heat without its atmosphere being able to retain it. 

The reason for this is that the planet's surface reflects 30% of the heat it receives (therefore loses 70%) this gives the planet a bond albedo of just 0.3. This is just enough more than Neptune (0.29) to mean that its colder despite its proximity to the Sun.

What's The Weather Like on Uranus?

Because of Uranus's odd tilt, for most of the year, the planet's poles receive the lion's share of the Sun's heat compared to the equator's of other planets in the Solar System.  Intuitively you would think this cause convection currents from the heated pole to the other but this doesn't happen.

'Weather', for want of a better word, on the planet is more or less identical to Jupiter and Saturn. Weather systems tend to break up into bands that rotate around Uranus. 

Wind speeds tend to reach around 900 km/hr which do appear to change close to the planets equinoxes when its rings can be seen on the edge. 

It may also rain on the planet, but not the way you might expect.

Uranus weather
Source: news.wisc
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