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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.
(Score: 2) by gidds on Thursday February 23 2017, @09:02AM
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.)
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?
[sig redacted]
(Score: 2) by bzipitidoo on Thursday February 23 2017, @10:52AM
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
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?
sudo mod me up
(Score: 2) by bzipitidoo on Thursday February 23 2017, @07:58PM
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.