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posted by on Wednesday February 22 2017, @01:02PM   Printer-friendly
from the i-can-be-a-planet-too! dept.

Scientists against the demotion of objects like Pluto, Eris, Sedna, etc. to "dwarf planet" status have crafted a new definition:

It's no secret that Alan Stern and other scientists who led the New Horizons mission were extremely displeased by Pluto's demotion from planet status in 2006 during a general assembly of the International Astronomical Union. They felt the IAU decision undermined the scientific and public value of their dramatic flyby mission to the former ninth planet of the Solar System.

But now the positively peeved Pluto people have a plan. Stern and several colleagues have proposed a new definition for planethood. In technical terms, the proposal redefines planethood by saying, "A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters." More simply, the definition can be stated as, "round objects in space that are smaller than stars."

From the proposal:

The eight planets recognized by the IAU are often modified by the adjectives "terrestrial," "giant," and "ice giant," yet no one would state that a giant planet is not a planet. Yet, the IAU does not consider dwarf planets to be planets. We eschew this inconsistency. Thus, dwarf planets and moon planets such as Ceres, Pluto, Charon, and Earth's Moon are "fullfledged" planets. This seems especially true in light of these planets' complex geology and geophysics. While the degree of internal differentiation of a given world is geologically interesting, we do not use it as a criterion for planethood in the spirit of having an expansive rather than a narrow definition.

Here's another article about the significance of the New Horizons mission. New Horizons will fly by 2014 MU69 on January 1, 2019.


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  • (Score: 5, Insightful) by bzipitidoo on Wednesday February 22 2017, @01:46PM

    by bzipitidoo (4388) on Wednesday February 22 2017, @01:46PM (#470150) Journal

    The IAU could have and should have waited until this year to redefine planet. I have no problem with Pluto being redefined as a dwarf planet. What I found objectionable was the timing. They knew the first probe to visit Pluto was on the way. They could have waited for the probe to arrive and send back its data, thus increasing our knowledge of Pluto more than a thousandfold. Was a great reason to wait, not least because the additional information would surely help with the decision. If that wasn't enough, in the same year we also had the first probe to visit Ceres, another object once granted planetary status.

    That they didn't wait was a slap in the face to NASA and America. I wonder how many astronomers were motivated by that, rather than pure science. The decision just feels so rushed, like they were eager to demote Pluto before getting a close look at it and Ceres.

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  • (Score: 0) by Anonymous Coward on Wednesday February 22 2017, @04:03PM

    by Anonymous Coward on Wednesday February 22 2017, @04:03PM (#470236)

    Well, we have the data now. What does it tell us?

    Also is being a planet like being a US state vs. a US territory? Do I have to pay income tax if I live on a dwarf planet? Why do I care if it's a "planet" or not? "Planet" is a human word and like most things human too vague while at the same time being too nitpicky. The universe doesn't care whether that big hunk of rock that crosses Neptune's orbit every now and then is a planet or not. But if it changes how I submit my taxes to the UEE then I might care.

    I mean will I have to move to Eris if I want to keep being exempt from UEE income tax? Eris is smaller but not much. What about Makemake or Sedna? Could I just hop skip and jump to Charon? Are all those planets now because they're round? Even Luna! Can't even live on "the moon" if I want to avoid income tax! Should I build my space shack on Miranda if I want to be safe? Is that too round? What about Deimos?

    • (Score: 0) by Anonymous Coward on Wednesday February 22 2017, @04:07PM

      by Anonymous Coward on Wednesday February 22 2017, @04:07PM (#470240)

      Oh I should also note to remember that "planet" means "wanderer." Maybe the only planets should be the original wanderers visible to the unaided human eye? Sorry Neptune! Your whole hood ain't planets no more! I'll settle down in Triton and call it good.

    • (Score: 1) by charon on Wednesday February 22 2017, @05:41PM

      by charon (5660) on Wednesday February 22 2017, @05:41PM (#470294) Journal
      Sorry, my gravity is so low you could jump to escape velocity. You would probably not enjoy living on me.
      • (Score: 0) by Anonymous Coward on Wednesday February 22 2017, @11:35PM

        by Anonymous Coward on Wednesday February 22 2017, @11:35PM (#470517)

        Are you round?

    • (Score: 0) by Anonymous Coward on Wednesday February 22 2017, @11:29PM

      by Anonymous Coward on Wednesday February 22 2017, @11:29PM (#470513)

      > Do I have to pay income tax if I live on a dwarf planet?

      Stop terraforming taxation!

  • (Score: 2) by gidds on Thursday February 23 2017, @09:02AM

    by gidds (589) on Thursday February 23 2017, @09:02AM (#470648)

    The fly-by still happened, and we still got the same data from it we would have done otherwise.  How was any of that affected by what nomenclature we assign it?

    And the proposed new definition makes even less sense.  By including satellites such as the Moon (which is still a large object, but the barycentre of the Earth-Moon system is well inside the Earth, showing the Moon's secondary role) and Ceres (one of a millions asteroids that differs only in happening to be large enough to attain hydrostatic equilibrium), that cheapens the definition, and leaves no term for planets that do dominate their area enough to clear their orbit, and aren't captured by a bigger one.

    In fact, if we were to redefine 'planet' in that way, I predict that we'd simply coin a different term for what we currently call 'planet' — and that that term would eventually come to dominate anyway.

    ('That which we call a planet by any other name...', &c &c.  I agree that 'dwarf planet' isn't a very good term, but an alternative such as 'planetoid' might have solved this without so much fuss.)

    That they didn't wait was a slap in the face to NASA and America.

    Er, sorry, why bring politics into this?  Is the USA now so insecure, so fearful, that it has to see even something as objective as science as a personal attack?  Having run out of real enemies, it now has to conjure up more imaginary ones?

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    [sig redacted]
    • (Score: 2) by bzipitidoo on Thursday February 23 2017, @10:52AM

      by bzipitidoo (4388) on Thursday February 23 2017, @10:52AM (#470663) Journal

      New Horizons was very much the people's probe. It was built and launched because the people gave high priority to the mission of visiting the last unvisited planet that we knew of. If Pluto had been demoted even earlier, New Horizons might never have happened.

      Why politics? Well, why else was the redefinition of planet done so hastily? Why the rush? There was no scientific reason for the timing, there really wasn't, while there was reason to wait. Apart from having lots more data that bears upon the decision, and the problems with the new definition, it would have been courteous to wait a little longer. That they didn't wait could reflect anger at the policies and propaganda that lead to the Iraq War that the US started in 2003, whatever they may claim about being above politics. After all, Pluto is the only planet to have been discovered by America. It's also possible that many just didn't like the idea of the solar system having possibly hundreds of planets, instead of just 8. Hardly scientific to be prejudiced against numbers larger than 10.

      • (Score: 2) by TheRaven on Thursday February 23 2017, @11:27AM

        by TheRaven (270) on Thursday February 23 2017, @11:27AM (#470670) Journal

        Well, why else was the redefinition of planet done so hastily? Why the rush?

        Are you a defence contractor? If not, what do you work on where 'over a period of about 15 years' is considered to be a rush?

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        sudo mod me up
        • (Score: 2) by bzipitidoo on Thursday February 23 2017, @07:58PM

          by bzipitidoo (4388) on Thursday February 23 2017, @07:58PM (#470866) Journal

          This is outer space we're talking about. Takes years to get places. Sending a probe to the nearest star system, Alpha Centauri, and getting back the data absolutely can't be done in less than 8 years, without faster than light travel. We are nowhere close to being able to probe Alpha Centauri at all, takes 9 years just to get to Pluto. So, yeah, 15 years is rushing it when they knew lots more data was coming in 9 more years.