How many of you think Pluto should have stayed a planet?

Answer 1

No, I50 years ago there were 12 planets and realising that more bodies would have a strong case for inclusion if Ceres Pallas Juno and Vesta were to remain as planets the astronomers of the day demoted them in the 1860s from the status they had enjoyed for 50 or more years since their discovery in 1801-1807. We can imagine the emotional reaction of the public at the time. But time passes, and who now remembers they were once regarded as planets? Indeed who now knows that they were and that we once had 12 planets?

(If you think I am making that up, that only proves my point, as to how memory fades and then people don't know about it, even a generation later). Pluto will, I fear, similarly get forgotten, especially as the category of "dwarf planet" starts to fill up,

The solar system bodies that will attract the public interest in the future will; be those that are found to have life, or can perhaps be colonised (Mars, Europa, Enceladus and Titan are strong candidates) or have unusual features (the tourist in all of us). (Both Uranus and Neptune are now known to both have ring systems if not as spectacular and eerie as Saturn's).

And in the event of an extra-solar planet being found with life on it, and nearby, too that will just take over and swamp everything else (the nearest two stars with planets, Epsilon Eridani (one known planet, a second one is suspected) and Gliese 876 (three planets) are respectively 10.5 and 15.4 light years away).

And Giordano Bruno who predicted the existence of both extra-solar planers and extra-terrestrial life on them, and was burned at the stake in 1600 by the Roman Catholic church for these heresies, is likely to overtake Galielo Galilei as the best-known and "greatest" astronomer ever, as a consequence.

So my predictions are that Pluto's memory will first wane slowly and then suddenly be totally eclipsed by the excitement of life being found somewhere else.

But to return to assessing Pluto's demotion, and why it happened, and the historical precedent for it ...

Pluto was reclassified in a 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 problem 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

It is conceivable the IAU may create more categories in the future in the light of more discoveries, The moment we find an extra-Solar System planet with extra-terrestrial life on it, for example, I would expect Habitable Zone Planet to be a new category and only Earth and Mars of our local 8 planets to be in it.

We already have the distinction between a terrestrial planet (the inner 4 planets) and a gas giant (the outer 4 planets) and are assessing new extra-Solar-System planets in the light of that distinction and a new category name for the informally-named "hot Jupiters" (i.e. large planets orbiting near to their star at less than 1 AU distance) of which we know several, may not be far away,

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 continuing to admit other, newly discovered bodies to the planetary club that were similar to the ones they decided 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 Herschel felt 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,

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 discussed,

SO: Pluto should not be a planet, nor should it be just another TNO or small solar system body, It has been given a status intermediate between these two extremes and that is how it should now be seen.

Answer 2

Hello,

I think it should have definitely stayed a planet. Before it was discovered, there was much speculation and mystery about its existence. Scientists at the time called it "planet X". Many searched for this mysterious planet but only one man found it.

What he did was memorize a great many stars in the sky. Then he would look at photographs of the stars. He would do this over and over, for years until he found a star that "moved". Of course stars don't really move like a planet and the light that changed position on his photograph must have been "Planet X" later named Pluto.

I really admire this guys dedication and contribution to science. He proved in a very low tech way that it is possible to make significant scientific discoveries through sheer persistence and dedication. I think the only proper way to honor this man is to keep Pluto as a planet.

Those who do not want to keep Pluto as a planet have probably contributed squat to science. I think they are all underachievers getting attention in any way they can. I think they all should be fired and made to work at MacDonald's.

Answer 3

Regardless of the petty descriptions that astronomers have given to Pluto which no longer regard it as a "planet" is absolutely ludicrous. The "planet" Pluto remains a planet because it orbits our Sun and has at least two moons of it's own. I'm an amature astronomer and as far as I'm concerned Pluto is to this day a "Planet"...period...and will remain a planet in the hearts of everyone who grew-up in the world with Pluto as a planet. Pluto doesn't exist within the asteroid belt between Mars and Jupiter; it is a solitary body that orbits the Sun with at least two smaller bodies (moons) orbiting Pluto. If THAT doesn't classify it as a Planet, then I as an astronomer, have no idea what the so-called "professionals" use to classify a Solar-orbiting body as a "planet".

Answer 4

Warmsoapy gives eloquently the logical scientific answer, but the discovery of Pluto by Tombaugh, its naming by a young English girl whose father was an astronomer (she is still alive, her story is delightful) creates an atmosphere of emotional values that transcends or compliments sheer logic. Tombaugh passed on a few years ago, but his widow was just interviewed, and has a splendid sense of humor. She feels that she was demoted from wife of the discoverer of a planet to wife of the discoverer of a dwarf planet. When Pluto was discovered, there was no idea that other small planets of similar size were also orbiting about out there. It was a moment of great excitement and awe, the discovery of another planet. For all these reasons, I think Pluto should be grandfathered in, reinstated as a fully fledged member of the solar system, perhaps as the only "honorary planet", sort of like giving an honorary degree to someone who has excelled in some field. Imagine how Pluto would feel, if it could. It would be utterly heartless to continue to leave it demoted after so many years of acceptance. Also, the widow of Tombaugh would be delighted to regain her former position of planetary spouse-hood.

Answer 5

i don't know how many, but i have been waiting for this since i was about twelve. i feel somewhat satisfied. this was the right thing to do, believe me. i don't understand why so many are having such a problem with this.

the international astronomical union defined three terms "planet", "dwarf planet", and "small solar system body". this does not change anything about the solar system or pluto. it just corrects the mistake of classifying pluto as a planet initially. i don't know how long this will drag on tho. many planetary scientists are not satisfied that the definition is rigorous enough.

because pluto orbits the sun, is round, does not have an isolated orbit (a bunch of other similar bodies have similar orbits.), and is not a satellite it is a dwarf planet.

look here:
http://en.wikipedia.org/wiki/Kuiper_belt
http://www.iau.org/fileadmin/content/pdfs/Resolution_GA26-5-6.pdf

Answer 6

Absolutley not! If Pluto is a planet, then there are currently well over 40 other planets and possibly more than 100 undiscovered ones!

Answer 7

I'm not sure about the scientific clarification, but I reckon it should have stayed a planet, because it is easier for kids to understand that the coldest planet (and farthest) is Pluto!

Answer 8

No. Pluto and its "moon" Charon are just big snowballs on the fringes of our solar system in a region called the Kepler Belt. Pluto doesn't fit into either of the two categories of planets, the small, rocky planets in the inner regions of the solar system, nor the large, gaseous planets of the outer regions of the solar system. It is a small, insignificant chunk of ice that doesn't fit with either of the two established planet classes found in our solar system.

Answer 9

No. Because it doesn't fit with the other 4 before it, and the other 4 before them. There could be countless Pluto's out there... although it does feel a bit lonely without her in the solar system.

Answer 10

What does it matter if Pluto is not a planet? It is an interesting object for astronomers , and is still there where it was. It just has a different adjective- that's all.

Answer 11

I do because it is circulating the sun the same as other planets, and it has a moon circulation it. I think it is a spat between astronomers going for personal glory.
It's all in the definition and the definition of a planet is one which circles the sun in orbit, not circle another planet as one of the so called new planets is doing.
It's the doing of people who want change so their names will be out front in astronomy