Neil deGrasse Tyson is wrong about Pluto

On yesterday’s Rachel Maddow show, guest Neil deGrasse Tyson- astronomer at the Hayden Planetarium – confirmed again his position that Pluto was indeed “demoted” from planetary status, and then proceeded to try to explain why. This also provided air time in advance of his PBS program: ‘The Pluto Files: The Rise and Fall of America's Favorite Planet', chronicling his experience at the center of the controversy over Pluto's planetary status.

My issue then as now is WHY did this controversy arise in the first place? Also why confect an artificial definition for a planet – e.g. “it must clear its orbital zone around the Sun” – when the definition itself is obviously based on trying to demote Pluto? (Somewhat analogous to the BLS definition of the “unemployed” – which drops everyone still unemployed after 6 months as “discouraged?) Pardon me, but I have strong issues with tampering with people’s neural networks and language centers via euphemisms, lies and cynical manipulations.

The issue here isn’t so much about being exercised at Pluto’s demotion, as the gravitas which we attach to language and especially scientific procedures and processes. The bottom line is that Pluto’s dethroning was done by a subjective vote at an IAU meeting, not by any objective measures or consistency. (Though doubtless deGrasse Tyson would argue otherwise).

But let’s examine it more closely.

As it turns out, Tyson’s Hayden predecessor – Dr. Kenneth R. Franklin- during a 1975 stopover at Barbados (and after giving a guest lecture at its Harry Bayley Observatory), was asked a question on the possible demotion of Pluto. The questioner wanted to know, given we knew so little about Pluto (Viking hadn’t even landed on Mars yet) whether a possible demotion to a comet or asteroid might be in the works if we discovered it was much smaller than then believed. (At that time, it was presumed to be about 3600 miles in diameter or about the size of Mercury).

Franklin’s answer – which I captured on audiotape- was clear and distinct:

“That depends. If someday it’s found that Pluto is only half as large as Mercury or even less, BUT if it’s found around the same time to have satellites of its own, then it is still a planet.”

Thus in one clear concise definition, Franklin disclosed how and why even a planet found to be much smaller than originally thought, can retain its status. And, of course, the Plutonian moon Charon was discovered in 1978, just three years after Franklin’s visit, while two other moons – Nix and Hydra- were found in 2005.

Another definition of a “planet” was offered by Dr. Isaac Asimov, both in his book, ‘The Collapsing Universe’ and in his own February 6, 1975 lecture at Queen’s Park Theater in Barbados. The definition was that a legitimate planet is gravitationally attracted to the Sun more than it is to any ancillary satellites or Moons it may possess. In doing some back of the hand math on a chalkboard, Asimov actually showed the Moon is a planet in its own right, since it is attracted more to the Sun than to the Earth. If he was alive and could do similar calculations for Pluto – I know he’d also concur it was a planet.

But let’s go back to the absurd definition that a true planet has nothing substantial crossing its path as it orbits the Sun. The problem is the definition overlooks the neighborhood of the object! Pluto just happens to be in the Edgeworth –Kuiper belt with thousands of other objects. This is a condition of happenstance, not of actual intrinsic property.

If Earth were to interchange its position with Pluto it would also be in the same belt, and because other substantial objects (e.g. Neptune) crossed its path, it would have to be demoted – by deGrasse Tyson’s definition. So what to call it, a “demi-Earth”? A jumbo dwarf planet or jumbo shrimp planet? Give me a break!


In the end, the error of the planetary astronomers in the 2006 confab was to cave in to a certain contingent of peer pressure to avoid “complexity”, e.g. in adding numerous additional planets like Charon, Xena, Ceres etc. This, despite the fact the original IAU definition was perfectly rational in its criteria for a planet.

Alan Stern, executive director of the Space Science & Engineering Division of the Southwest Research Institute – and Principal Investigator for NASA’s New Horizons mission to Pluto- observed that the new planet definition was “sadly flawed, particularly due to the vagueness of the third condition”, e.g. clearing the neighborhood around its orbit – which might also disqualify Earth!

He added: “A lot of people are going to ignore the (new) definition because it doesn’t make sense.” (Source: Eos Transactions of the American Geophysical Union, Vol. 87, 29 August, p. 350)

Again, this isn’t about getting into a pickle over definitions specifically, but attending to the objective processes of science – especially in an era in which denialism is rampant, and looking for any excuse to reject critical findings – such as anthropogenic global warming.

The tragedy of the Pluto vote and the accompanying contrived definition is that it's not only set back planetary astronomy – showing the preponderance of ego over scientific inquiry – but public confidence in science as well. In such a climate, one can’t be too surprised when spurious crises like “climate gate” arise, since their genesis is directly connected to the lack of attention current scientists are paying to their QA processes and the presentation of their respective disciplines overall.