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10 Naming, Classification & Observation Controversies of our Solar System

For a long, long time it seemed like the parts of our solar system were pretty well fixed and decided. Since the discovery of Pluto not much was changed. Sure, we discovered more moons around Saturn and Juptier when various probes flew around them, and discovered less prominent rings around gas giants not named Saturn, but for the most part things did not change. That is, until we started discovering a bunch of trans-Neptune objects and a lot of conventions went out the window: Pluto was demoted to Dwarf Planet status and despite people holding popularity contests to re-instate it as a planet it has remained a Dwarf Planet

But this sort of thing is actually nothing new. In fact the history of Solar System astronomy from Galileo to the present day is riddled with odd controversies like naming conventions, egoism, nationalism, lost chances, new classifications & credit-stealing  that have dogged the history of local astronomy. Here are just 10 incidents or controversies to make realise that the reclassification of Pluto wasn’t anything new.

10) Nationalism rears its ugly head: Uranus was discovered in 1781 and its discoverer, Herschel, wanted to name it after King George III. So he

"Named after a mortal King? How gauche!"

“Named after a mortal King? How gauche!”

termed it ‘The Georgian Planet’. English sky almanacs listed it this way for decades, but needless to say it was not a popular convention outside of England. Other suggestion made were to name it after Herschel, or call it Neptune(!). The final decision was not made until 1850 to name the planet Uranus.

9) Egoism rears its ugly head: Neptune, the furthest planet from our Sun (now that Pluto is a Dwarf Planet), was discovered by astronomer La Verrier in 1846 (he did not actually first observe it, he did the

"At least you were named after a King!"

“At least you were named after a King!”

calculations as to where it could be found). Once discovered, La Verrier wanted to name the planet after himself. To support this naming convention, France released almanacs that listed Neptune as La Verrier and Uranus as Herschel. This did not placate England (who felt that their astronomer, Adams, deserved credit – more on that later) much less the rest of the astronomy world. The name Neptune was suggested, and Laverrier as a planet name lasted only a short time (Georgian Planet, however, lingered).

8) I’m a planet! No, I’m not! Pluto’s demotion is not a new thing. The asteroid Ceres was discovered

"I feel your pain, Pluto".

“I feel your pain, Pluto”.

in 1801 and was quickly classified as a planet. But less than a year later more asteroids were discovered and classifying them all as planets was problematic. It took a while for the convention ‘asteroid’ to be accepted and Ceres was listed as a planet for decades. Now with the new classification of Dwarf Planet, Ceres has been promoted from an asteroid to a Dwarf planet as it fits all the criteria given for that designation.

7) Almost got it! Galileo almost discovered Neptune. In his notes he observed the distant planet while observing Jupiter. The two planets were very close while he was observing. However, Neptune was undergoing its retrograde

"I wonder if...nah.."

“I wonder if…nah..”

motion (where the planets go backwards in the night sky because of the motion of the earth around the sun) and appeared motionless. Galileo considered it to be a fixed star and ignored it. His telescope was not good enough to show details that might indicate it was not a star. Centuries later, an examination of his notes and diagrams was done because someone realized that when Galileo was observing Jupiter when it was in Conjunction with Neptune. Sure enough, it turned out that Galileo was the first human to view the distant planet due to some pure luck, but he couldn’t determine what it actually was.

6) Credit where credit isn’t due: La Verrier wasn’t the only astronomer to lay claim to discovering Neptune. English astronomer Adams also claimed that his calculations led to its discovery. This of course

"Curse You Dennis Rawlins!"

“Curse You Dennis Rawlins!”

caused butting of heads between English and French nationalist astronomers. Finally it was agreed that they would share credit as co-discoverers. However, over a hundred years later, serial credit denier Dennis Rawlins claimed that Adams did not deserve credit for co-discovery as his calculations were way off and almost more harmful than useful (The actual poisition of Neptune was 1 degree from where LaVerrier claimed and 12 degrees from where Adams claimed). It turns out that Rawlins was correct in this case. International astronomers examined the evidence and found Adams should not deserve credit for the discovery. LaVerrier is now considered Neptunes sole discovered. This decision was not made until the late 1990’s.

5) “But, we’re not of Greco-Roman Origin!” The planets are named after Roman gods, which where stolen wholesale from the Greek gods. But Greco-Roman culture did not permeate the entire word. What about Asia? Africa? Native Americans? Indians? Arabs? Well, on the bright planets all of these cultures have their own names. But when it came to the outer planets they were surprisingly clever at adhering to the naming convention. Most cultures, for example, name Neptune after their own historical sea-gods. If they didn’t have a sea-god they would name them after sea monsters. Uranus was a bit trickier as it was a sky god and many cultures do not have such a equivelant diety, so names like ‘Sky King Star’ or ‘Sky God Star’ become the convention.

4) Vulcan, the non-planet (No, we are not talking about Star Trek): When an odd pattern in Mercury’s orbit was discovered in 1859, Newtonian physics could not explain the problem. A solution was suggested that another planet between Mercury and the sun existed that was exuding gravitational force on Mercury. Did we mention this was suggested by LaVerrier, the Neptune discoverer? He suggested this planet be named

"Just get used to me. "

Just get used to me.

Vulcan and requested astronomers search for it. Soon after this was proposed many folks started claming to see this theoretical planet either transiting the sun or with direct observation. Most of these observations were unfounded or unreliable, but one done by astronomer Lescarbault was enough to satisfy Laverrier and he announced its discovery in 1860. Many astronomers were skeptical, and there were many false alarms with sunspots being mistaken for Vulcan. But the problem of Mercury’s orbit remained. Laverrier died and the search for Vulcan waned. In 1915 Einstein solved the problem as being an effect of the strong gravitational effect of the sun having a relativistic effect on Mercury that was much diminished on further planets.

3) Canals on Mars: In the later 19th century, several astronomers reporting seeing ‘channels’ or ‘canals’ on the surface of Mars. Some of them were even mapped. It was even suggested that these channels were artificially Lowell_Mars_channelsdug canals that showed intelligent life on the red planet. As telescope optics improved it was noted that reports of canals dropped off. It turns out that seeing canals on Mars was actually an optical illusion that was an artifact of lower-grade optics. A few adherents stuck with these old canal reports until Mariner 4 mapped the martian surface and showed no such features.

2) Planet X: LaVerrier (again!) noticed some oddness in the orbit of Uranus in the 19th century, this was confirmed by several other observations. It was proposed that a large planet, designated ‘Planet X’ existed past Neptune that was causing this

"I'm not Planet X, but I have a heart!"

I’m not Planet X, but I have a heart!

orbital issue. When Pluto was discovered it was hoped that it was the answer, but Pluto turned out to be too small. Several other searches for Planet X were made but turned up nothing. Some crazies got a hold of the idea and imagined it was doing ludicrous things like hiding behind the Hale-Bopp comet. Eventually the Planet X hypothesis was abandoned when space probe data revealed the error in Uranus’ orbit was caused by a overestimation of the mass of the planet.

1) Phaeton & Titus-Bode Law: You doubtless know of Newton’s Laws of Gravitation, and have probably heard of Kepler’s laws of Planetary Motion. But have you ever heard of of the Titus Bode-Law? (someties just called

"Everything is fine so fa....awwww"

“Everything is fine so fa….awwww”

Bode’s Law). This was a Law that stated that each planet orbiting the sun will be approximately twice the distance from the previous planet. So Venus will be twice the orbit of Mercury, Earth twice the orbit of Venus, etc. This Law got a boost when it was used to find Ceres, which filled the gap between Mars and Jupiter. Since Ceres was not an impressive planet, some proposed it was actually part of a broken or exploded planet they dubbed Phaeton (and idea still suggested by pseudo-scientists today). The discovery of more asteroids lent hope to this idea, but the total mass of the asteroids later found was not enough to make a ‘real’ planet. Bode’s Law got a boost with having an approximate location of Uranus, but flopped badly when used for predicting Neptune’s location.  The Law is now obviously discredited.




What happened to Pluto?

As you may well know, a few years ago there was quite a bit of controversy in the Astronomical circles when the long beloved Pluto was demoted from being a planet to a new classification ‘dwarf planet‘. There was much lamenting of this decision. Even today a search of ‘Pluto’ on Facebook will turn up not less than a half-dozen groups lamenting the fact that Pluto was demoted.

Many gripe that the only planet discovered by an American tainted the decision, some demand  it remain a planet  for nostalgia’s sake. Only a few folks know the reason why Pluto is now classified like it is:

  First of all, let us understand that this is not the first time this has happened! In the past people once considered Ceres to a be planet. It was actually listed as such in most educational texts of the time. But as more discoveries of asteroids were made that classification changed as well. More on Ceres in a little bit.

Pluto was considered a planet from its discovery in the 1930’s to only about 5 years ago. The seeds of the problems started when Chiron, discovered in the 1970’s was spotted in what would be known as the Kuiper Belt.  But Astronomers effectively shelved the problem and dealt with other science issues.  This gave Pluto a reprieve from scrutiny for almost 30 years. But then more discoveries were made.

The discovery of Eris (nicknamed ‘Xena’ for a short time) by Mike Brown (who incidentally twitters under the name ‘Plutokiller’) in 2005 made it apparent that there was a lot more such planets in the Kuiper belt. The discoveries of more Kuiper belt denizens soon cascaded. Something had to be done about classification of these new objects and the international astronomers dithered and delayed once more.

Enter Neil deGrasse Tyson, the world’s sexiest Astrophysicist according to ‘People’ magazine and director of the Hayden Planetarium in New York City.

Neil was working with the American Natural History Museum to put in a display of the planets of the solar system. They wanted to classify the planets by type. That is the rocky planets (Mercury, Venus, Earth, Mars) and the Gas Giants (Saturn, Jupiter, Neptune, Uranus).  From there they would have special descriptions of each planet’s unique features.

This classification presented a big problem: Pluto doesn’t fit into either category. It certainly isn’t a gas giant, but it is not a rocky planet either. In fact, structurally speaking, Pluto has more in common with Comets than with the planets of the solar system. If Pluto were to break orbit and fly towards the sun, it would actually develop a tail just a like comets do! This made its classification very hard to do. There were other issues as well – while we have excellent photos of all the planets – some of them from even before the various  space probes were launched – we had very few decent images of  Pluto, partly because of its structure. In fact the photo you see near the top of this article is actually one of the best shots of Pluto ever taken, and it is still just a dot of light!

So Neil and the developers of the Hayden museum simply did not put in a display for Pluto. But then the media noticed the missing Pluto. Soon there were articles in New York newspapers decrying the lack of a Pluto and Neil’s explanation that Pluto might be recategorized was not enough. Now astronomers around the world had to make a decision: they could ignore the structural issues of Pluto, they could ignore Chiron in the 70’s, they could ignore the recent discovery of other Kuiper belt objects, but they could not ignore the media attention.

So there were some meetings of international astronomers to make some decisions. Part of the problem is that there wasn’t really a good definition of what a ‘Planet’ really is! ‘Planet’ simply means ‘wanderer’ in ancient Greek and referred to those objects that meandered forward and backwards in the sky compared to the stars around them. That was caused by retrograde motion but it led to their terminology. When new objects were discovered, such as Neptune and Uranus, the same term was used for them. There was only one glitch – when Ceres was discovered and termed a planet – until many more objects in the same region were discovered and a new term ‘asteroid’ was applied.

At first, not wanting to surrender Pluto as a planet they astronomers came up a with a rather poor definition. It was decided that any object that had sufficient mass to make a spherical shape and orbited the sun would be considered a planet. This decision, while saving Pluto from a status change, caused more problems than it solved. It meant that Ceres was once again a planet, and that the dozen or so Kuiper belt objects would also be classified as such. Our Solar System would now go from 9 planets to potentially over 20! This would not work.

So soon another decision was reached and a new condition was added. To be considered a planet an object had to meet three classifications:

1) Be in orbit around the sun

2) Be of sufficient size to form a roughly spherical shape


3) “Cleared its neighborhood” of other bodies.

This 3rd classification is what demoted Pluto. It had captured a moon: Charon, but the area of its orbit was still filled with other objects. Pluto had not cleaned its room. It was demoted from planet-hood.

But what to call the new objects? If they filled the first two qualifications they would be designated a new classification:  ‘dwarf planet’, sometimes referred to as “plutoids”.  Pluto and many of the newly discovered Kuiper belt objects went into this new category – and celestial poster-makers had to add a line saying ‘Pluto is no longer considered a planet’ to their prints.

Oddly enough, what was bad for Pluto was good for Ceres. After it had been demoted from being a Planet  to being an Asteroid in the 19th century, Ceres is now promoted to Dwarf Planet status. It is the only Dwarf Planet not int he Kuiper Belt or further out (although another asteroid, Vesta, might be classified as such – the Vesta probe will arrive in July of this year (2011) to determine more about its shape!

As astronomer Phil Plait put it, this really was no more than a distraction.  While we may be fond of our childhood mnemonic devices that help us remember the planets names, in the end it really doesn’t matter what we call a celestial object. Each one is unique and will have to be studied for its special features. With planets being discovered in other solar systems all the time we now have even more concerns and things to study rather than worry about what to call something. In the end, it is just a name.

Note: This article is a re-write from Spectrum Scientifics old blog.