Is Pluto going to be taken out of the science curriculum as ninth planet in the solar system?

Question

Pluto is not a planet anymore. It is now called a dwarf planet. Will Pluto be used in the curriculum?
What is going to happen to the exhibits in museums which feature Pluto (talk about its details)?

Answer 1

The best way to use the recent events in Prague in teaching about Pluto is to explain why it was necessaty to change its category. as an example of how science classifies objects and sometimes needs to re-classify them in the light of new discoveries and on reflection, i.e. science is an organic developing thing. not writ on tablets of stone which are held to be true for all eternity. It is capable of self-criticism and capable of refutation.

Indeed, Karl Popper once argued that it is intrinsic to a scientific theory, unlike a religious dogma, that it is open to being disproved. Or, we might add, to being qualified or amended or refined to be more precise and accurate and useful.

I quote from a long poem by Bertolt Brecht called In Praise of Doubt:

"Oh how laboroiously the new truth was fought for!
What sacrifices it cost!
How difficult it was to see
That things were thus and not thus!
With a sigh of relief one day a man entered it in the record of knowledge

For a long time perhaps it stands there, and many generations
Live with it and regard it as eternal wisdom
And the learned scorn all who are ignorant of it.

And then it may happen that a suspicions arises, for new experience
Makes the established truth open to question. Doubt spreads
And then one day a man thoughtfully strikes it out
From the record of knowledge."

Bertolt Brecht (1898-1956)

I happen to think the best way to teach the fall of Pluto from grace is to teach the previous expulsion of Ceres, Pallas, Juno and Vesta from the planetary club and to draw the historical parallels between the two events.

EXECUTIVE SUMMARY:

Pluto suffered much the same fate and for much the same reasons as 1 Ceres, 2 Pallas, 3 Juno and 4 Vesta, which were all initially classified as planets on discovery and then, 50 or more years later, demoted from planetary status in the 1860s, and the number of planets then fell from 12 to 8 as a result.

There are several parallels between the two situations, worth noting. We really have "been here before".

(1) they were all five felt to be disappointingly small but despite that were accepted as planets ...

AS

(2) there was no other category to put them in, when discovered, as they were the first of a new "breed" of objects to be found, and it wasn't realised at first there were any others like them.

(3) it was predicted there would be a "missing" planet where Ceres was found (by the Titius-Bode Law of planetary semi-major axes) (which had gained hugely in credibility when Uranus was found in 1781 at almost exactly the distance from the Sun that the Titius-Bode Law suggested another planet, if there were one, would be found.)

Similarly Pluto's existence was surmised from gravitational "wobble" in the orbit of Neptune and astronomers then hunted for years for a missing planet that would fit the bill.

When Ceres (in 1801) and Pluto (in 1930) were finally found and found roughly where they were anticipated to be, it almost inevitably made the planet-seekers convinced that it was a planet they had found: i.e. they were predisposed to considering it as a planet, given it was a planet for which they had been hunting for some years.

(4) after they were discovered, a lot of further similar bodies were then discovered and if the first of their kind had have remained as planets, the case for admitting growing numbers of other such bodies would have been overwhelming and the numbers of planets would, it was feared, rapidly have soared "out of control".

(5) so a new category (asteroids, then and dwarf planets now) was invented and defined and the demoted ex-planets placed in it.

THE STORY IN FULL

Pluto was reclassified two weeks ago at a meeting of the International Astronomical Union in Prague, in a new, different category (dwarf planet) of Solar System objects from the one it previously was classified under,

What we have just witnessed in Prague is an exercise in scientific classifiation of the objects this branch of science studies, i.e. bodies in the Solar System and other extra-solar systems.

The basic probem Pluto has and had from the outset is that it is smaller than 7 moons in the Solar System: Ganymede, Io, Europa and Callisto (the 4 Gallilean moons of Jupiter) Titan (Saturn's largest moon) Triton (Neptune's largest moon) and our own Moon, all of which were discovered before Pluto.

Heirarchical thinking that Planets "ought" to be bigger than Moons and "size-ism" prejudice doubtless played a part in the recent IAU decision, But only a minor part. Mercury is smaller than the two biggest moons, Ganymede and Titan and it didn't get downgraded, did it?

So; whilst there is understandable dismay at Pluto being demoted in status, people really need to understand the reasons the IAU had to grapple with definitions and categories at this time:

(1) in 1930 we knew of just one body lying beyond the orbit of Neptune. Now we know of more than 1000

(2) we are discovering asteroids at a rate of 5000 a month

(3) we now know of 200+ extra-solar planets orbiting 170+ other stars, some of which we now know to have asteroid belts

As science expands its knowledge, it needs more concepts and categories with which to describe and classify that knowledge, That is perfectly normal and should neither surprise nor alarm us,

Creating new categories and reclassifying known objects in the light of them has happened before: in the 19th Century when the number of planets was pruned from 12 to 8 out of concern that being consistent and admitting other, newly discovered bodies to the planetary club that were similar to the ones they chose to kick out instead would have meant the number of planets could rapidly start to escalate and mushroom "out of control",

To understand what is going on now, it helps to understand what went on then,

The number of bodies in the Solar System known to astronomers has been burgeoning for a long time now, but the general public seems unaware of this, given the way people blithely talk of Ceres (discovered 1801) Charon (discovered 1978) and Xena (discovered 2003) having "just been discovered",

There was a similar definitions crisis in the early 19th century and again in the mid-19th Century as the number of known objects in the Solar System started to grow and grow,

By 1807 the 8 Solar System bodies known to classical astronomy (the Sun, the Earth, our Moon and the 5 classical planets known from antiquity, Mercury, Venus, Mars, Jupiter, and Saturn) (1 star, 6 planets, 1 moon) had grown to 26. Uranus was found in 1781 making 7 planets. There were 4 Jovian moons, 7 Saturnine moons and 2 Uranian moons, 14 in all

And then there was the discovery of the first four asteroids. These were 1 Ceres on January 1, 1801, 2 Pallas on March 28, 1802, 3 Juno on September 1, 1804, and 4 Vesta on March 29, 1807,

What were astronomers to call these new objects? They weren't moons as they rotated around the Sun, so they had to be planets, didn't they? As there was, initially, no other category but moons or planets to put them in.

After 2 Pallas was discovered though, Sir William Herschel (the discoverer of Uranus) coined the term "asteroid" meaning "star-like"), in 1802.

But Ceres was meantime assigned a planetary symbol, and remained listed as a planet in astronomy books and tables (along with 2 Pallas, 3 Juno and 4 Vesta) for about half a century until further asteroids were discovered.

So we now had 1 star, 11 planets and 14 Moons, the beginnings of a distinction between major and minor planets and a sense of unease as to what we would do if more asteroids were discovered as the first four were all disappointingly small in size, so did they really belong in the planetary club? (Similar doubts were expressed about Pluto, right from the outset in 1930,)

38 years pass and then in 1845 the asteroid 5 Astraea is discovered and on September 23, 1846 the planet Neptune and a mere 17 days later on October 10, 1846, Neptune's moon, Triton. (We now have 1 star, 12 Planets 15 Moons and 1 non-planetary Asteroid.)

The pace of discovery then starts to really hot up. Four more asteroids in nine months: 6 Hebe on July 1, 1847, 7 Iris on August 13, 1847, 8 Flora on October 18, 1847, and 9 Metis April 25, 1848

Then on September 16, 1848 an 8th moon of Saturn called Hyperion is discovered,

Plus a further 6 asteroids are found in just over two years: 10 Hygiea on April 12, 1849, 11 Parthenope on May 11, 1850, 12 Victoria on September 13, 1850, 13 Egeria on November 2, 1850, 14 Irene on May 19, 1851 and 15 Eunomia on July 29, 1851.

And on October 24, 1851 a 3rd and a 4th moon of Uranus: called Ariel and Umbriel were discovered.

So now we had 42 objects: 1 star 12 planets 18 moons and 11 asteroids. If the latest asteroids were all to be regarded as planets, making a total of 23 planets (and 10 Hygiea was bigger than 3 Juno, just like Xena is bigger than Pluto), it was likely to start getting silly (by 1868 the number of asteroids was to rise to 107 and Victorian schoolchildren would have needed a massive 115-word mnemonic to remember all the names).

The unease grew to a crisis, a redefinition was clearly necessary and an inevitable decision was taken to regard all 15 asteroids as a separate category from planets and Ceres, Pallas, Juno and Vesta were kicked out of the planetary club, just like Pluto has been kicked out now.

There are some clear parallels between the situation in the 1850s and the situation now, Four under-sized runts had obtained planetary status, with seemingly more to follow as they were discovered, creating an overwhelming feeling among astronomers that the currency would be devalued if all these further objects were to then be automatically awarded planetary status. So they cried Whoa! And called a halt. And created a new category, Just like the IAU has now done,

SO HOW MANY OBJECTS HAVE WE GOT IN THE SOLAR SYSTEM NOW?

Stars: 1

Planets: 8

Moons: over 80 known moons of the dwarf planets, asteroids and other small solar system bodies.

(The asteroid 87 Sylvia has 2 moons for example as does the Kuiper Belt Object KBO 2003 EL61.)

AND another 162 moons orbiting around planets: Mercury has none, Venus has none, Earth has 1, Mars has 2, Jupiter has 63, Saturn has 56, Uranus has 27, Neptune has 13.

Kuiper Belt Objects: over 800 (all discovered since 1992).

Trans-Neptunian Objects: over 1000 (includes the 800+ KBOs) i,e, there are 200+ in the Scattered Disk and the Oort Cloud.

Asteroids: Hundreds of thousands of asteroids have been discovered within the solar system and the present rate of discovery is about 5000 per month. As of July 23, 2006, from a total of 338,186 registered minor planets, 134,339 have orbits known well enough to be given permanent official numbers. Of these, 13,242 have official names.

Current estimates put the total number of asteroids above 1 km in diameter in the solar system to be between 1.1 and 1.9 million

So you can see

(a) why some definitions are needed and why reclassification is necessary

(b) how totally unaware of the state of scientific knowledge the general public is and how uninformed people are when they get excited at tales of "3 new planets being discovered" and wonder if there might perhaps be more where those came from,

THE BIGGER PICTURE

Finally, these issues need to be seen in the context of the 205 extra-solar planets we now know to exist and the asteroid belts that have now been detected in some of those stellar systems,

Consistency being a desirable thing to achieve in science, whatever definitions and categories the IAU now adopt, they need to be applicable to every star with other objects in orbit around it, throughout the entire universe, That is the context in which Pluto's status is now being reassessed,

Answer 2

For at least a few years people will probably mention it's formerly being called a planet and incorporate the new definitions into the curriculum. Later teachers (and exibits) will probably either talk about Pluto along with all other Dwarf Planets or not talk about it specifically but explain what a Dwarf Planet is, after all they already talk about other comets (what Pluto is technically) and asteroids.

Answer 3

Yes, it will be taken out of the Science curriculum as a ninth planet in the Solar system. One good thing about this modern Internet age is that we are more accustomed to rapid changes, especially in Information. So, the impact of the change would be quickly absorbed. Afterall, it is just a definition. And as long as there are sufficient adoption, it will stick. For those things such as encyclopedia, referenece materials, books, etc. They will be phased in by new editions over time. For now, people will make a mental note of the change in Pluto status.

Answer 4

Yes. It's going to change. Pluto never really met the definitions for 'planet', and since Pluto's discovery they've found as many as 50 objects very similar to it. The largest is named Xena. Because of this there's a new class of space object being written up. Right now they're being called 'dwarf planets', but the official name might be 'Plutonians' due to Pluto's change of category and it was the first of the dwarf planets to be discovered. The same thing happened to asteroids when they were discovered.

Answer 5

In the short term, the new terminology will creat a buzz and more curricula will include Pluto. After a few decades, however, the curriculists will begin to lump it with asteroid belts and other "lesser" bodies.

Answer 6

Since this is basically a topic of classification, it is not really a critical issue. If anything, I think it is good for people to see the discrepency, so as to remind them of the everchanging nature of science.

Answer 7

I like pluto

Answer 8

They (museums etc.) will change the data. Plain and simple. The faster the media (like wikipedia, it was changed within minutes), the faster it's changed.

Answer 9

i have been waiting for this since i was about twelve. i feel somewhat satisfied. this was the right thing to do, believe me. as i understand, the hayden planetarium does not have pluto depicted in its model of the planets.

http://amnh.org/rose/

Answer 10

going to be? It's alraedy done. It was reclassified as a dwarf planet now.