# Pluto to be a planet again? **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [October 3, 2014, 12:32am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224 "2014-10-03T00:32:54Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [October 3, 2014, 12:32am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/1 "2014-10-03T00:32:54Z")
> **[Wait, what? Pluto a planet again?](https://www.freep.com/story/news/nation/2014/10/02/pluto-planet-nasa/16580517/)** > > Pluto might be making its way back into the solar system fraternity. Owen Gingrich himself is apparently advocating for it: > [@](#): > > Harvard science historian Owen Gingerich, who chairs the IAU planet definition committee, argued at a forum last month that “a planet is a culturally defined word that changes over time,” and that Pluto is a planet. Take _that_ Neil deGrasse Tyson! Although it could be that the Mi-Go threatened to put Tyson’s brain in a labeled box with wires attached… ---
**Author:** ![boffking](https://avatars.discourse-cdn.com/v4/letter/b/858c86/32.png) [@boffking](https://boards.straightdope.com/u/boffking)\ **Post date:** [October 3, 2014, 2:57am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/2 "2014-10-03T02:57:00Z")
So how exactly is the IAU defining a “planet” now? ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [October 3, 2014, 3:49am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/3 "2014-10-03T03:49:02Z")
> [@boffking](#): > > So how exactly is the IAU defining a “planet” now? > **[IAU definition of planet](https://en.wikipedia.org/wiki/IAU_definition_of_planet)** > > The International Astronomical Union (IAU) defined in August 2006 that, in the Solar System, a planet is a celestial body that: > A non-satellite body fulfilling only the first two of these criteria (such as Pluto, which had hitherto been considered a planet) is classified as a dwarf planet. According to the IAU, "planets and dwarf planets are two distinct classes of objects" – in other words, "dwarf planets" are not planets. A non-satellite body fulfilling only the first criterion is termed a sma... ---
**Author:** ![buddy431](https://avatars.discourse-cdn.com/v4/letter/b/6a8cbe/32.png) [@buddy431](https://boards.straightdope.com/u/buddy431)\ **Post date:** [October 3, 2014, 4:45am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/4 "2014-10-03T04:45:14Z")
If Pluto’s made a planet, then so must Ceres and Sedna. No special treatment because a generation of kids grew up with you. ---
**Author:** ![blue\_infinity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_infinity/32/2817_2.png) [@blue\_infinity](https://boards.straightdope.com/u/blue_infinity)\ **Post date:** [October 3, 2014, 5:29am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/5 "2014-10-03T05:29:00Z")
I approve of this. The de-planetting of Pluto was completely political; a backroom hatchet-job. Very little to do with science. > [@buddy431](#): > > If Pluto’s made a planet, then so must Ceres and Sedna. No special treatment because a generation of kids grew up with you. The more the merrier. ---
**Author:** ![marshmallow](https://avatars.discourse-cdn.com/v4/letter/m/df705f/32.png) [@marshmallow](https://boards.straightdope.com/u/marshmallow)\ **Post date:** [October 3, 2014, 6:19am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/6 "2014-10-03T06:19:41Z")
> [@blue\_infinity](#): > > The more the merrier. If Pluto is a planet there are potentially hundreds, maybe thousands of kuiper objects that could qualify. They’re more like each other than anything else, similar to the largest inhabitants of the asteroid belt not being planets either. [Are these all planets?](http://upload.wikimedia.org/wikipedia/commons/thumb/7/72/Iau_dozen.jpg/800px-Iau_dozen.jpg) ---
**Author:** ![blue\_infinity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_infinity/32/2817_2.png) [@blue\_infinity](https://boards.straightdope.com/u/blue_infinity)\ **Post date:** [October 3, 2014, 6:39am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/7 "2014-10-03T06:39:51Z")
Yes. If they orbit the Sun, and they have assumed hydrostatic equilibrium - they are planets. A simple and elegant definition. This is how science should work. You define a problem, and you accept the answer. Whether it’s 9 or 20 or a hundred. You do not pick the answer that you want (8 in this case) and then create a cockamamie, opaque formula to arrive at the answer. ---
**Author:** ![Don\_t\_Panic](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/don_t_panic/32/398_2.png) [@Don\_t\_Panic](https://boards.straightdope.com/u/Don_t_Panic)\ **Post date:** [October 3, 2014, 7:03am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/8 "2014-10-03T07:03:17Z")
> [@blue\_infinity](#): > > Yes.A simple and elegant definition. “Make things as simple as possible, but not simpler.” Personally, I think keeping my socks, underwear and shirts in one big pile on the floor, instead of in separate drawers, is simple and elegant. Doesn’t mean it’s a sensible idea. How many planets are there in the solar system? Simple: “Eight, and these are their names.” Simpler, and about as practical as a one-legged horse: “A whole bunch, and I’m fucked if I know what they’re all called.” ---
**Author:** ![blue\_infinity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_infinity/32/2817_2.png) [@blue\_infinity](https://boards.straightdope.com/u/blue_infinity)\ **Post date:** [October 3, 2014, 7:09am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/9 "2014-10-03T07:09:03Z")
I believe in your metaphor it’s only the shirts that are in the drawer. The socks and underwear are all in a big pile on the floor, and you’re trying not to notice them. ---
**Author:** ![wolf\_meister](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolf_meister/32/15202_2.png) [@wolf\_meister](https://boards.straightdope.com/u/wolf_meister)\ **Post date:** [October 3, 2014, 8:22am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/10 "2014-10-03T08:22:34Z")
The official IAU definition of a planet states > [@](#): > > 1. is in orbit around the Sun, > 2. has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and > 3. has “cleared the neighbourhood” around its orbit. But that is not very precise. (especially rule #3) I’m all for restoring Pluto’s planetary status, and maybe I’m defining “planet” just for this reason. How about 1.) Orbits the Sun at less than 50 astronomical units 2.) Is round 3.) Has a diameter greater than 2,000 kilometers. At least it is a very _precise_ definition of planet. Yes, with my rule #1, I’m purposely eliminating Eris and Sedna. However, if there were an Earth-like planet that obits the Sun at 1 light year should that be considered a planet? I don’t think so. And rule #3 eliminates Ceres. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [October 3, 2014, 8:33am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/11 "2014-10-03T08:33:35Z")
> [@blue\_infinity](#): > > You do not pick the answer that you want (8 in this case) and then create a cockamamie, opaque formula to arrive at the answer. Right. You should pick the answer that you want, and then create a simple transparent formula to arrive at the answer. I suggest “known before 1931” ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [October 3, 2014, 8:45am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/12 "2014-10-03T08:45:59Z")
> [@buddy431](#): > > If Pluto’s made a planet, then so must Ceres and Sedna. No special treatment because a generation of kids grew up with you. OK, but for uniformity of the naming conventions, _Sedna_ should be renamed _Goofy_. (I don’t care if it upsets Sheldon.) ---
**Author:** ![Don\_t\_Panic](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/don_t_panic/32/398_2.png) [@Don\_t\_Panic](https://boards.straightdope.com/u/Don_t_Panic)\ **Post date:** [October 3, 2014, 8:52am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/13 "2014-10-03T08:52:52Z")
Maybe Pluto could get its own category. I suggest “dwarf-like object, gravitationally-rounded”, or “DOG”. ---
**Author:** ![iiandyiiii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/iiandyiiii/32/7924_2.png) [@iiandyiiii](https://boards.straightdope.com/u/iiandyiiii)\ **Post date:** [October 3, 2014, 11:06am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/14 "2014-10-03T11:06:50Z")
Pluto really is different than the other 8 planets – it’s much less dense (for the solid portion), it’s much smaller, and it has a different origin. But in the same way, Mercury/Venus/Earth/Mars are very different from Jupiter through Neptune. So maybe we ought to have three categories – gas giants, rocky planets, and iceballs of a certain size. Either way, I don’t believe Pluto belongs in the same category with the other 8 planets. ---
**Author:** ![blue\_infinity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_infinity/32/2817_2.png) [@blue\_infinity](https://boards.straightdope.com/u/blue_infinity)\ **Post date:** [October 3, 2014, 11:59am UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/15 "2014-10-03T11:59:46Z")
> [@Melbourne](#): > > I suggest “known before 1931” So Ceres (1801) is in? > [@iiandyiiii](#): > > But in the same way, Mercury/Venus/Earth/Mars are very different from Jupiter through Neptune. So maybe we ought to have three categories – gas giants, rocky planets, and iceballs of a certain size. This is kind of the issue, Jupiter has more in common with the Sun then it does with Earth. The IAU has no problems lumping them in together, but excludes Pluto. ---
**Author:** ![iiandyiiii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/iiandyiiii/32/7924_2.png) [@iiandyiiii](https://boards.straightdope.com/u/iiandyiiii)\ **Post date:** [October 3, 2014, 1:01pm UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/16 "2014-10-03T13:01:04Z")
> [@blue\_infinity](#): > > This is kind of the issue, Jupiter has more in common with the Sun then it does with Earth. The IAU has no problems lumping them in together, but excludes Pluto. I don’t think this is true at all, with regards to Jupiter and the Sun. Planets don’t have nuclear fusion going on inside them – stars do. That alone makes planets like Jupiter and Earth much more similar to each other than either is to a star like the Sun. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [October 3, 2014, 1:08pm UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/17 "2014-10-03T13:08:37Z")
> [@iiandyiiii](#): > > I don’t think this is true at all, with regards to Jupiter and the Sun. Planets don’t have nuclear fusion going on inside them – stars do. That alone makes planets like Jupiter and Earth much more similar to each other than either is to a star like the Sun. That’s like saying that an unlit candle is a completely different thing than a lit one. ---
**Author:** ![iiandyiiii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/iiandyiiii/32/7924_2.png) [@iiandyiiii](https://boards.straightdope.com/u/iiandyiiii)\ **Post date:** [October 3, 2014, 1:17pm UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/18 "2014-10-03T13:17:28Z")
> [@Alessan](#): > > That’s like saying that an unlit candle is a completely different thing than a lit one. Huh? Are you saying Jupiter could be “lit”? Because it couldn’t be. Star fusion is a matter of mass – for fusion to take place, there needs to be sufficient mass, and Jupiter is not even close. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [October 3, 2014, 1:18pm UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/19 "2014-10-03T13:18:34Z")
Well the unlit candle has the potential to sustain a flame while a gas giant can not sustain stellar fusion. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [October 3, 2014, 1:24pm UTC](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224/20 "2014-10-03T13:24:05Z")
> [@Alessan](#): > > That’s like saying that an unlit candle is a completely different thing than a lit one. Jupiter isn’t a candle. It might be a blob of wax, just enough to roll between your fingers but not enough to make a candle. [Next page](https://boards.straightdope.com/t/pluto-to-be-a-planet-again/700224.md?page=2)