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If this object did exist, wouldn't it be classified as a dwarf planet since, like Pluto, with a highly elliptical orbit it would be difficult to clear it of oth

If this object did exist, wouldn't it be classified as a dwarf planet since, like Pluto, with a highly elliptical orbit it would be difficult to clear it of other Kuiper belt objects?

alex_young 5y ago
An object with multiple Earth masses could hardly be classified as a dwarf planet.
- kbelder 5y ago
  "A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite." According the the wrong-headed AIU definition. So, yes, _Jupiter_ could be a dwarf planet, if it hasn't cleared it's orbital neighborhood for some reason.
  - robocat 5y ago
    https://en.wikipedia.org/wiki/Clearing_the_neighbourhood https://en.wikipedia.org/wiki/Clearing_the_neighbourhood Weird definition since it prevents deciding if an exoplanet is a planet or a dwarf planet. It smells like a compromise proxy measure for: orbital stability, in a reasonably circular orbit, plus rule out Pluto. Maybe there is some deep reason for using that measure, but it is not obvious.
    - bnralt 5y ago
      As far as I can tell, many planetary scientists aren't particularly fond of the definition either. I believe the initial plan that the IAU had after the discovery of Eris was to classify dwarf planets as planets, but some of the members didn't like the idea that our solar system would suddenly get a lot more planets, so pushed for the current awkward and ill-defined IAU definition. Though there are a lot of people that present the IAU definition as if it were simply the will of "science," if you look at the 2006 debate about it amongst scientists, it was actually fairly contentious.
- vikingerik 5y ago
  It very well could. Defining a planet as major or dwarf goes by its ability or inability to "clear the neighborhood", to control or remove objects of smaller mass in its orbital area. 225 AU is a long way, and the volume of space to clear goes up quadratically with distance; this object would have 50,000 times more space to clear than does Earth. The orbital period also goes up with distance [edit, reply is right that it's the 3/2th power], so so does the time between interactions with any particular object. Multiply those together and you would have an object more than cubically (3.5th power) less effective than Earth at clearing its neighborhood over time, such that it may not have happened in the lifetime of the solar system.
  - lanna 5y ago
    > The orbital period also goes up quadratically with distance By Kepler's Third Law, isn't it proportional to the square root of the cube (3/2th power) of the distance?
  - ithinkso 5y ago
    It's on a plane. Circumference goes up lineary
    - vikingerik 5y ago
      It's undefined whether "clearing the neighborhood" involves the spheroid at that distance or just the plane. It hasn't come up, since all eight known major planets do satisfy the three-dimensional criterion. We'd probably revise or clarify the definition if we discovered an object that cleared its plane but not its volume.
  - dylan604 5y ago
    >ability or inability to "clear the neighborhood", who said it has finished the job? has the correct paper work be filed? according to the permits in the galactic construction offices, the work is not scheduled for completion for a few hundred more millennia.
skykooler 5y ago
I think the criteria are more along the lines of "gravitationally dominate its orbit", which due to the perturbations of KBOs this object would do. Otherwise, basically all planets would be demoted (e.g. Neptune has not cleared its orbit because Pluto is there, Jupiter hasn't because of the Trojans, etc.)
readthenotes1 5y ago
"Scientists who search for Planet Nine estimate that its mass is several times bigger than Earth’s... " So no. It won't be a dwarf planet.
slyall 5y ago
I asked Mike Brown this on twitter earlier this year and he said it will have cleared out it's orbit so that won't be a problem. " definitely clears! " https://twitter.com/plutokiller/status/1433802812945625095 https://twitter.com/plutokiller/status/1433802812945625095
odyssey7 5y ago
The sufficient-but-not-necessary conditions for identifying a planet are called into question as a workable definition once more. We’ve duck-typed the solar system, I guess.
- SkittyDog 5y ago
  I hate to be the one to break the bad news to you, but... That's pretty much how all science works. https://en.m.wikipedia.org/wiki/Species_concept https://en.m.wikipedia.org/wiki/Species_concept Categorization is a leaky abstraction. Use them when they're useful, and ignore them when they become more trouble than they're worth.
  - odyssey7 5y ago
    At risk of maybe going too far on a tangent, I understand this idea and the species example is a good one. The planets are different because they were first defined as mystical and cultural concepts, before they could be understood as scientific ones. There are plenty of people who still think about the planets as cultural concepts rather than scientific ones. (What is a Jupiter? It’s a thing in space that our culture has named “Jupiter.”) I think we should define the planets the way co-star does. By listing them: DATA PLANET = MERCURY | MARS | ETC Scientists can have their own definitions of things, but they will face resistance if they try to dictate culture through their definitions. https://www.costarastrology.com/why-haskell/ https://www.costarastrology.com/why-haskell/
    - SkittyDog 5y ago
      I'm pretty sure animal and plant species also existed as cultural and mystical concepts, long before science was a thing. All of your analysis can be applied equally well to species, as well as planets... Or the four seasons (winter, spring, summer, autumn) or the five Oceans, or the seven Continents. They're all simply human attempts to impose neat category boundaries across a continuum of natural phenomena that are definitely not neat. Categories can be useful, but they often lead to pointless arguments by lay people (a la Pluto's relegation) when we start to fetishize a human-created category structure as an essential expression of underlying reality. It's just plain old human narcissism.

If this object did exist, wouldn't it be classified as a dwarf planet since, like Pluto, with a highly elliptical orbit it would be difficult to clear it of other Kuiper belt objects?

alex_young 5y ago

An object with multiple Earth masses could hardly be classified as a dwarf planet.

kbelder 5y ago
"A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite." According the the wrong-headed AIU definition. So, yes, _Jupiter_ could be a dwarf planet, if it hasn't cleared it's orbital neighborhood for some reason.
- robocat 5y ago
  https://en.wikipedia.org/wiki/Clearing_the_neighbourhood https://en.wikipedia.org/wiki/Clearing_the_neighbourhood Weird definition since it prevents deciding if an exoplanet is a planet or a dwarf planet. It smells like a compromise proxy measure for: orbital stability, in a reasonably circular orbit, plus rule out Pluto. Maybe there is some deep reason for using that measure, but it is not obvious.
  - bnralt 5y ago
    As far as I can tell, many planetary scientists aren't particularly fond of the definition either. I believe the initial plan that the IAU had after the discovery of Eris was to classify dwarf planets as planets, but some of the members didn't like the idea that our solar system would suddenly get a lot more planets, so pushed for the current awkward and ill-defined IAU definition. Though there are a lot of people that present the IAU definition as if it were simply the will of "science," if you look at the 2006 debate about it amongst scientists, it was actually fairly contentious.
vikingerik 5y ago
It very well could. Defining a planet as major or dwarf goes by its ability or inability to "clear the neighborhood", to control or remove objects of smaller mass in its orbital area. 225 AU is a long way, and the volume of space to clear goes up quadratically with distance; this object would have 50,000 times more space to clear than does Earth. The orbital period also goes up with distance [edit, reply is right that it's the 3/2th power], so so does the time between interactions with any particular object. Multiply those together and you would have an object more than cubically (3.5th power) less effective than Earth at clearing its neighborhood over time, such that it may not have happened in the lifetime of the solar system.
- lanna 5y ago
  > The orbital period also goes up quadratically with distance By Kepler's Third Law, isn't it proportional to the square root of the cube (3/2th power) of the distance?
- ithinkso 5y ago
  It's on a plane. Circumference goes up lineary
  - vikingerik 5y ago
    It's undefined whether "clearing the neighborhood" involves the spheroid at that distance or just the plane. It hasn't come up, since all eight known major planets do satisfy the three-dimensional criterion. We'd probably revise or clarify the definition if we discovered an object that cleared its plane but not its volume.
- dylan604 5y ago
  >ability or inability to "clear the neighborhood", who said it has finished the job? has the correct paper work be filed? according to the permits in the galactic construction offices, the work is not scheduled for completion for a few hundred more millennia.

skykooler 5y ago

I think the criteria are more along the lines of "gravitationally dominate its orbit", which due to the perturbations of KBOs this object would do. Otherwise, basically all planets would be demoted (e.g. Neptune has not cleared its orbit because Pluto is there, Jupiter hasn't because of the Trojans, etc.)

readthenotes1 5y ago

"Scientists who search for Planet Nine estimate that its mass is several times bigger than Earth’s... " So no. It won't be a dwarf planet.

slyall 5y ago

I asked Mike Brown this on twitter earlier this year and he said it will have cleared out it's orbit so that won't be a problem. " definitely clears! " https://twitter.com/plutokiller/status/1433802812945625095 https://twitter.com/plutokiller/status/1433802812945625095

odyssey7 5y ago

The sufficient-but-not-necessary conditions for identifying a planet are called into question as a workable definition once more. We’ve duck-typed the solar system, I guess.

SkittyDog 5y ago
I hate to be the one to break the bad news to you, but... That's pretty much how all science works. https://en.m.wikipedia.org/wiki/Species_concept https://en.m.wikipedia.org/wiki/Species_concept Categorization is a leaky abstraction. Use them when they're useful, and ignore them when they become more trouble than they're worth.
- odyssey7 5y ago
  At risk of maybe going too far on a tangent, I understand this idea and the species example is a good one. The planets are different because they were first defined as mystical and cultural concepts, before they could be understood as scientific ones. There are plenty of people who still think about the planets as cultural concepts rather than scientific ones. (What is a Jupiter? It’s a thing in space that our culture has named “Jupiter.”) I think we should define the planets the way co-star does. By listing them: DATA PLANET = MERCURY | MARS | ETC Scientists can have their own definitions of things, but they will face resistance if they try to dictate culture through their definitions. https://www.costarastrology.com/why-haskell/ https://www.costarastrology.com/why-haskell/
  - SkittyDog 5y ago
    I'm pretty sure animal and plant species also existed as cultural and mystical concepts, long before science was a thing. All of your analysis can be applied equally well to species, as well as planets... Or the four seasons (winter, spring, summer, autumn) or the five Oceans, or the seven Continents. They're all simply human attempts to impose neat category boundaries across a continuum of natural phenomena that are definitely not neat. Categories can be useful, but they often lead to pointless arguments by lay people (a la Pluto's relegation) when we start to fetishize a human-created category structure as an essential expression of underlying reality. It's just plain old human narcissism.