Pluto is no longer a planet - WHY

[Icosahedron]

Once a planet, always a planet...

How about if they put some further definition to 'gravitationally rounded' to discount some of the elliptical almost-planets but still include Pluto? Or include a 'not located in a belt' clause.

 

[aramis]

Once a planet, always a planet...

How about if they put some further definition to 'gravitationally rounded' to discount some of the elliptical almost-planets but still include Pluto? Or include a 'not located in a belt' clause.

Not located in a belt excludes Pluto. It's a near-ish KBO. Not located in a belt also excludes, to the same degree, Neptune, because several KBOs cross neptune's orbital distance.

 

[AndreaV]

Not located in a belt excludes Pluto. It's a near-ish KBO. Not located in a belt also excludes, to the same degree, Neptune, because several KBOs cross neptune's orbital distance.

Pretty much the only definition that will include Pluto and not include a heck of a lot of other things would be something with a clause like "or has historically and culturally been regarded as a planet" And I imagine I have a fair idea of what the chances of that being adopted are

 

[aramis]

Pretty much the only definition that will include Pluto and not include a heck of a lot of other things would be something with a clause like "or has historically and culturally been regarded as a planet" And I imagine I have a fair idea of what the chances of that being adopted are

It was explicitly voted down by the IAU on day one of the 2006 meeting.

They wanted a working definition. Certain members wanted something that excluded Pluto and Xena (now Eris).

Note that Traveller's size S roughly matches the minimum for gravitational rounding - 200-500km.

 

[saundby]

Wow, not sure if I should start, since it's hard to know when to stop on this subject...

Lessee, though.

First, by seeking to define what is and isn't a planet, IAU is exceeding the terms of their charter. They have the authority to name them, but not define what they are.

The vote taken that gave us the present confusion was taken in a way that violates the IAU's own rules. There are a surfeit of other reasons it was handled poorly, besides.

However, the IAU has bypassed the chance to revisit the question. I believe this to be because waiting a bit serves various parties here. Those that want a decision theoretically "untainted" by the controversy want to wait until the controversy subsides. Those who are in agreement with the current decision want folks to get used to things as they are and accept them. Those in opposition want to wait for New Horizons to bolster their case.

In the politics of science, there are many who felt that redefining Pluto et al as not-planets would benefit scientific work concerning them. They felt that they were competing for dollars against Jupiter and Saturn missions, and that a redefinition would sidestep that. They have been, to my knowledge, disappointed in the effect the decision has had on funding discussions with politicians and their funding bodies.

Also, there was an element of nationalism involved, aside from Dr. Tyson's influence and the funding myths.

The issue of whether a dwarf planet is or is not a planet was not officially settled. The measure voted on to define dwarf planet as a subtype of planet was defeated (in the procedurally flawed voting mentioned above), but nothing that officially defines it as not a subtype of planet has been passed, either. I has just been assumed and spread in passim without actual authority.

The same with speculation about how many KBOs may qualify as dwarf planets. In fact, the swing of evidence at present is that larger bodies may be much more rare than supposed at the time of the vote. The study of these objects is in its infancy, we really don't have much information.

And the bottom line is that what constitutes a planet is not a scientific question but a cultural one. My own belief is that it should be defined on this basis, and that a scientific body is really making a mistake by trying to issue an ukase on the use of the term. 'Planet' has already been redefined repeatedly to suit the cultural views of different times. The Sun was once a 'planet', in fact.

I've written an article here:
http://astrobasics.blogspot.com/2010/09/is-it-planet-or-not.html

It's painful to see kids being taught to pipe up with "Pluto is not a planet!" in a 'I'm so much more clever than you' tone, but that's what's happening. The fact is that it's far from a settled issue and the controversy makes science look like a bundle of strongly held opinions to the public. It's shameful.

Presently I teach* that the dwarf planets are among the 'planets' of the solar system, and have my students rehearse their names and information about them. I also teach that this is more an issue of nomenclature than science. by including them among the planets, I get the students to pay more attention to learning about these intresting bodies and our solar system as a whole than if they were shunted into another category (which would appear to be 'small things of no importance' to most students.)

In the classroom, at least, I get a better result when the discussion goes from some student's statement that Pluto's not a planet to introducing Eris and Haumea and Ceres and Makemake with details about each. We mark the orbital distances of all in the schoolyard, including noting the distance, size, and apparent brightness of each body as we go. It opens up more discussions about changing views of the solar system, improving instrumentation, the nature of knowledge, etc.

In other words, I try to make it serve the needs of education by inviting inquiry.

And the student who inevitably opens the planet discussion by declaring Pluto not a planet? I treat them with utmost consideration while opposing the nature of their statement. It's not their own view they're voicing, after all. I usually give them kudos for taking an interest, then go on to present the issue as an open one that's been poorly handled before getting back to the really interesting stuff that actually is science.

*Aside from my regular work in my profession, I teach part-time in a nearby public charter school to grades 7-12. Astronomy is one of my subjects.

 

[Epee]

If they have to name them, they have to define them (in order to know what, and how, to name).

The problem arose when technology surpassed tradition. Until the IAU's ruling, which like all scientific models can be changed, "Planet" meant the same thing since the Greeks with only some informal provision for asteroids.

 

[Whipsnade]

Presently I teach...

It's a shame we don't have more teachers like you.

 

[Putraack]

This was a fun read, IMO, by someone "on the inside."

http://www.goodreads.com/book/show/7963278-how-i-killed-pluto-and-why-it-had-it-coming

 

[aramis]

I was long term subbing in grade 5 when the definitions were passed. We were doing an astronomy unit.

The reports from the very next day included reactions from several IAU members who left because it had been tabled on day 2, and expected it to remain tabled until the next meeting, and were uninterested in the agenda for day 3. Then, Dr. Tyson apparently got it un-tabled on day three, when most of the opposition to the "cleared its neighborhood" had gone home.

The IAU has always defined what is and is not an ___ because of their control over naming ___. Comets get different names from minor planets, and minor planets from major planets. This new category, Dwarf Planets, gets major planet naming... while acknowledging that they are something different.

The whole funding issue should have been a no-brainer - funding for minor bodies probes has ALWAYS been a no-go with the US congress, a bit of a damper with the ESA funding protocols, and a lack of grants. DS1's mission to the minor planets was not approved as a minor planets mission, but a tech testbed project that happened also to do a minor planets survey.

New Horizons was approved because pluto was a planet - the redefinition resulted in a vote to abort the mission post-launch! (ISTR that vote being a committee vote.)

NASA funding has always been "Big Rocks Only". The ESA has been more flexible, but there's always been a big rocks bias.

Sadly, many working scientists are brilliant in field, but utterly ignorant about the realities of government funding. Grant writers are hired specifically to get the funding by knowing what funding sources will pay for and making the science look like that, even if they aren't.

 

[inexorabletash]

Ah yes, found the paper I liked on this topic:

http://arxiv.org/pdf/astro-ph/0608359v6.pdf

 

[aramis]

Ah yes, found the paper I liked on this topic:

http://arxiv.org/pdf/astro-ph/0608359v6.pdf

At least, unlike several of the other proposed definitions, he's got a clear definition of "gravitationally dominates" - even if his particular inclusions/exclusions are arguable. (Pluto, for example counting Neptune, nut Neptune not counting Pluto, due to resonant orbits...)

 

[BytePro]

It's a shame we don't have more teachers like you.

Second that!

And good post saundby!

In casual conversations I had with Alan Stern (New Horizon's PI) prior to the probe's completion - and long before the IAU meeting - I recall him referring to Pluto as a 'classical planet' to distinguish it from other bodies. I liked this (and fortunately, so did funding agencies!).

 

[saundby]

Thanks for the kudos.

One further comment on IAU's ability to name vs. classify:
When the IAU was formed, there was already precedent for kerfuffles over what is and isn't a planet. The naming function of the IAU was created to prevent nationalistic naming of bodies (proper names). The IAU would serve as an impartial organization to prevent that. For example, naming Pluto something like "Uncle Sam" or "Herbert Hoover" would not have flown.

The ability to designate what is and isn't a planet was withheld. The expectation was that national science bodies would fight this out. In part, because people in those bodies didn't want to "give up" the ability. And in part because some wanted the IAU to be "above" the sort of back and forth that had gone on with Ceres and the minor planets/asteroids.

The IAU has the ability to define classifications of other bodies, and to apply nomenclature to planets (e.g. gas giant, ice giant), but not to determine what is and isn't a planet, either through changes to nomenclature or through an explicit statement. The 2006 activity was an extension of the rules governing the IAU's activity. Successful, too, seeing as how the discussion in scientific circles and out has been mostly on the results of the decision, not on whether the right to make a decision existed.

The expected process is that a scientific body discovers what they consider a planet, they apply to the IAU to get a name from a list of preferences. The IAU can approve a name off the list, or ask for another list. If there's a challenge to whether the body is a planet, the IAU can't make a call on that, though they can offer to mediate. They can also select a name, with a statement that the status of planet is disputed. There's more to it than that--that's sort of the cracker-jack wrapper version.

Anyway, since none of this extends beyond our own solar system, this is probably going to be a tempest in a teapot once we start studying remote systems in detail, soon. You think the rules look confused now, wait a decade or so!

Personally, I think it's time to let people buy names for celestial bodies. And every dollar/pound/euro/rhinu over the 100,000 provided for process administration gets spent on astronomy and space exploration.

 

[aramis]

Thanks for the kudos.

One further comment on IAU's ability to name vs. classify:
When the IAU was formed, there was already precedent for kerfuffles over what is and isn't a planet. The naming function of the IAU was created to prevent nationalistic naming of bodies (proper names). The IAU would serve as an impartial organization to prevent that. For example, naming Pluto something like "Uncle Sam" or "Herbert Hoover" would not have flown.

The ability to designate what is and isn't a planet was withheld. The expectation was that national science bodies would fight this out. In part, because people in those bodies didn't want to "give up" the ability. And in part because some wanted the IAU to be "above" the sort of back and forth that had gone on with Ceres and the minor planets/asteroids.

The IAU has the ability to define classifications of other bodies, and to apply nomenclature to planets (e.g. gas giant, ice giant), but not to determine what is and isn't a planet, either through changes to nomenclature or through an explicit statement. The 2006 activity was an extension of the rules governing the IAU's activity. Successful, too, seeing as how the discussion in scientific circles and out has been mostly on the results of the decision, not on whether the right to make a decision existed.

The expected process is that a scientific body discovers what they consider a planet, they apply to the IAU to get a name from a list of preferences. The IAU can approve a name off the list, or ask for another list. If there's a challenge to whether the body is a planet, the IAU can't make a call on that, though they can offer to mediate. They can also select a name, with a statement that the status of planet is disputed. There's more to it than that--that's sort of the cracker-jack wrapper version.

Anyway, since none of this extends beyond our own solar system, this is probably going to be a tempest in a teapot once we start studying remote systems in detail, soon. You think the rules look confused now, wait a decade or so!

Personally, I think it's time to let people buy names for celestial bodies. And every dollar/pound/euro/rhinu over the 100,000 provided for process administration gets spent on astronomy and space exploration.

And just how many "Trump's Xth Star" do we need?

 

[Epee]

"A Rose by any other name would smell as sweet..."

Astronomical naming conventions, like other scientific naming conventions but more-so, can be confusing to say the least. Objects outside of the Solar System can be even less settled than those within. Stars, for example, can have a traditional name; Sirius, perhaps one or more colloquial names; Dog Star, and then any number of alpha-numeric designations singular to whatever stellar catalogue you happen to look at. Probably the only truely effective convention is listing by coordinate position and then a letter designation for each component of a multiple system, but this method does not exactly flow off of the tongue.

 

[Fritz_Brown]

Assuming, of course, that everyone uses the same coordinate system........

 

[saundby]

And just how many "Trump's Xth Star" do we need?

:rofl:

We'll charge him on the logarithmic scale!

 

[Epee]

Assuming, of course, that everyone uses the same coordinate system........

It'll do until we have to coord between stellar systems.

 

[atpollard]

It'll do until we have to coord between stellar systems.

You mean in 15 years when we achieve fusion power and enter TL 9?

 

[Carlobrand]

"A Rose by any other name would smell as sweet..."

Yup. Labels are a human thing; they sometimes mislead as much as inform. All the tempest doesn't alter its characteristics in the slightest. What really matters is it's so-and-so far out there, it's such-and-such a size, such-and-such surface gravity, such-and-such surface temperature, and what it would take for me to mine fuel for my pirate.:devil:

Oh, and whether there are any significant ore deposits that can be profitably exploited at that distance.

Long before this Kuiper Belt confusion, I recall some sci fi show mentioning Sol system and its ... I think it was 15 ... planets. Sounded like a joke then; seems prescient now.