How much more massive would Pluto have to be to clear its neighborhood?

How much more massive would Pluto have to be to clear its neighborhood?

How much more massive would Pluto have to be to clear its neighborhood?

This Wikipedia page does a decent job of describing the orbit-clearing criterion, based on the original paper by Stern & Levison (2002), which can be found here (PDF).

In order to have cleared its orbit over a period of billions of years, an object needs a "Stern-Levison parameter" $Lambda$ which is $> 1$; Pluto has $Lambda approx 3$-$4 imes 10^{-3}$. Since $Lambda$ depends on the square of the object's mass (see the Wikipedia page, or Equation 4 of Stern & Levison), Pluto would need to be about fifteen to twenty times its current mass in order to cross the threshold.

As we know, Pluto is within the Kuiper belt, and it only makes up about $0.077\%$ times the mass of all of the object within its orbit. Now, in comparison, Earth has objects in its orbit, but it is $1.7$ million times the mass of all of the objects.

It's been debated in the past (by supporters of Pluto being a planet) that if Earth were in Pluto's place, it wouldn't be able to clear the neighborhood. So, with Pluto being even smaller than Earth's moon, it would have to gain a significant amount of mass to be able to clear its orbit.

Pluto: Choose Your Side.

6 billion kilometers away, the culprit of an astronomical beat down is casually drifting through the outer rim of the solar system at a leisurely 4.7 kilometers per second. Once believed to be the 9th member of our solar system, Pluto kissed it’s courtship with planet-hood goodbye in 2006 when the IAU (International Astronomical Union) declared that the 2372 kilometer diameter ice ball was indeed not fit for the formal definition of a planet.

Despite being widely accepted as a dwarf planet by the scientific community, the fight for the re-installment of tiny Pluto into the solar system still wages on 10 years after the status demotion. With the flyby of the New Horizons spacecraft in 2015, tensions heightened between the Pluto-for-planet fighters and the firm poised, dwarf planet regulators.

With the announcement of theoretical planet 9 residing deep within the shroud of the Oort cloud, Pluto sympathizers retorted with arguments about how scientists could demote Pluto, but accept something even farther out and less fitting-in than Pluto, as a planet. But scientists, of course, go by their strict definitions in determining the planet-hood of any new celestial member.

As a student of science, I am inclined to accept Pluto’s modern designation as a dwarf. However, the child in me remembers reading about the nine planets out of my numerous astronomy books and wondering about the origin of this particular mysterious small world. Yes, a part of me still believes that Pluto should be a planet.

You Won’t Like The Consequences Of Making Pluto A Planet Again

Since its discovery in 1930, Pluto was heralded as the ninth planet in our Solar System. Pluto was the first world ever discovered beyond Neptune, and for nearly half a century, was the only world known beyond our last gas giant. Generations of schoolchildren learned mnemonic devices about their very educated mother just serving them nine pickles, with Pluto, the very last, lonely one out there, becoming the favorite of so many.

After 76 years, however, astronomers seemingly demoted Pluto to dwarf planet status, placing it alongside the large asteroid Ceres and other worlds out there in the Kuiper belt, reducing our Solar System’s planetary count to a mere eight. Last year, a team of scientists put forth a new definition of planet that would bring Pluto back into the fold, and this definition has been endorsed by Alan Stern and David Grinspoon, authors of a new book on the New Horizons mission and “the planet” Pluto.

Here’s what it would mean if we listened to them:

In 2006, the International Astronomical Union did something that no one had never done before, and gave a scientific definition to one of astronomy’s oldest terms: planet. The old “I-know-it-when-I-see-it” definition had come under fire for a variety of reasons, including the growing number of Trans-Neptunian objects found in the Kuiper belt and beyond. Many objects out there were round, with enough gravity to pull themselves into hydrostatic equilibrium. Some of them were even more massive than Pluto was. And there were a growing number of worlds being discovered around stars other than our own. Were all of these new objects planets? Some of them? None of them? And what about Pluto? The definition they put forth would not only ruffle feathers and spark controversy, it would immediately prove to be insufficient.

The IAU’s definition had just three statements:

  1. A planet had to be massive enough that its gravity would pull itself into hydrostatic equilibrium: round if it wasn’t rotating, but a spheroidal shape if it was.
  2. A planet had to orbit the Sun and no other object: Earth could be a planet but not the Moon.
  3. And finally, it had to clear its orbit, meaning there could be no other comparably large masses at the same orbital distance: Mars is a planet, but asteroids and Kuiper belt objects were all out.

Officially, under this definition, our Solar System was down to eight planets.

For astronomers who study our own Solar System, this is fine. For astronomical purposes, these eight planets have distinct properties that all the other worlds don’t. They are united by a similar, common formation history they influence the motion of the Sun and the other worlds more severely than any other worlds they reflect more sunlight than other worlds and they dominate, gravitationally, their portion of the Solar System. Eight planets, from many perspectives, is just the right number.

But this definition was dissatisfying to three very different groups: exoplanet astronomers, galactic astronomers, and planetary scientists.

The exoplanet astronomers have a very compelling argument. Why would a body orbiting our star, the Sun, be classified as a planet, but the worlds around any other star couldn’t be? It seemed like a tremendous oversight in 2006, as we had over a decade of discovered exoplanets behind us at that point. The rationale, after-the-fact, that was given by some was that there was no way to tell whether a planet had cleared its orbit or not from so far away. This may have been true in 2006, but nine years later, UCLA professor Jean-Luc Margot changed the game by devising a universal planetary test that didn’t require a spaceship! If you could learn the following three easy-to-measure parameters:

  1. the mass of the planet,
  2. its orbital distance/period around its parent star, and
  3. the lifetime of the planetary system in question,

you could determine, with better than 99% accuracy whether a body satisfies the three IAU criteria for being a planet.

Quite clearly, the eight planets of our Solar System are in, and the asteroids and Kuiper belt objects are out. Interestingly, if there were only the Moon rather than the Earth-Moon system orbiting the Sun, it would be right on the border between planet and non-planet. But then, for the galactic astronomers, what do you do for rogue planets? If you don’t have a parent star to orbit at all — either because you were born without one or you were ejected from your solar system — does that make you any less of a planet?

This is a tough question, because in astronomy — as in real estate — location is almost everything. Mercury, at the distance of Jupiter, would never clear its orbit and wouldn’t obtain planetary status. A world much smaller than Mercury could be a planet around a red dwarf star, while even Earth would fail to be a planet if it were out in the Oort cloud somewhere. And yet, we call so many of these non-planetary worlds “planets,” but with a prefix. We have dwarf planets, rogue planets, and exoplanets. In the early stages, we have protoplanets and planetesimals. But, at some level, aren’t all of them, plus more, still planets?

This argument gets taken to an extreme by some planetary scientists, as elucidated by Stern and Grinspoon in yesterday’s Washington Post. They contend that location should be ignored, and that if you’re massive enough to pull yourself into hydrostatic equilibrium (a sphere if you aren’t spinning a spheroid if you are), congratulations: you’re a planet. As you can see, above, this would mean that if we looked at the objects under 10,000 kilometers in diameter in our Solar System, there wouldn’t be two (Mars and Mercury) planets, but 109 of them. The Solar System’s total would rise to 115 planets, with 19 moons, one asteroid, and 87 objects beyond Neptune added to the current total of 8. And in the future, as we discover more objects in the Kuiper belt, the scattered disk, and even the Oort cloud, that number will rise further: perhaps into the thousands.

On the one hand, there are advantages to the arguments they make. When we talk about the geological, atmospheric, and geophysical properties of a world, we do, in fact, call them all planets. We call the field of studying these worlds planetary science, and when we talk about a world’s oxygen content, crust, composition, or potential for habitability, we have no qualms calling these measurable quantities “planetary properties.” On Pluto alone, we’ve learned that it has clouds, weather, snow, mountains, valleys, geological layers, and likely even a subsurface ocean. It has five moons it rotates on its axis it has days and nights and seasons. If you ignored its astronomical location, you’d call it a planet every time.

And yet, that’s the other hand: you have to ignore all of astronomy to consider Pluto a planet. That’s the question you need to ask yourself: should an object’s position in its Solar System determine what a planet is? Or should only the intrinsic properties of the world matter? Should we ignore, completely, the connection between planets and solar systems, stars, their formation, and the gravitational dance that has always fueled our knowledge and curiosity about them?

I resent the assumption that we will become less interested in Pluto, or in asteroids, comets, centaurs, moons, and the outer reaches of the Solar System, simply if we don’t name them “planets” also. There are just as many ambiguities under the geophysical definition as there are for the astronomical one: if something stripped Saturn’s gas away, would its round core still make it a planet? Is the asteroid Vesta, which has a crust, mantle, and metallic core, but isn’t quite round, up for consideration? Would a smaller, icy world (

200 km in radius) be a planet, because it’s round, while a larger rocky world (

250 km in radius) wouldn’t be?

The simple fact is that Pluto was misclassified when it was first discovered it was never on the same footing as the other eight worlds. The 2006 move by the IAU was an incomplete attempt to repair that mistake. The current move by Kirby Runyon, Alan Stern, and others is a step in the opposite direction: it’s a step towards making a larger, more confusing mistake that will render a definition meaningless to the majority of people who use it.

There are some out there who are desperate to save Pluto’s planetary status, and would be willing to open the floodgates and bestow planethood on every moon, asteroid, and ice ball out there that’s massive enough to be round. There are others who spend 100% of their time looking down at their feet on whatever world they’re considering when it comes to planethood, and to them, everything with enough mass will be a planet. But for the rest of us, where you are in the Universe is an inseparable part of what you are. Nothing in the Universe exists in a vacuum, and where you are determines a huge number of properties of you, regardless of whether you’re a planet, moon, asteroid, centaur, comet, Kuiper belt object, or Oort cloud object. If you want to ignore all of that — and proclaim, “round means planet” — then more power to you. But in planethood, as in most things, the full scientific story is far more interesting.

How much more massive would Pluto have to be to clear its neighborhood? - Astronomy

Many of the arguments I’ve read online are making a mockery of this debate, both pro and con. I have read logically fallacious appeals to tradition, arguing that Pluto should remain a planet because that’s what we were taught in school and that’s the way it has been for 76 years. On the other side of the aisle, I am reading equally spurious logic that there are enough planets and the fact that we will certainly discover more means there will eventually be too many. The media seems to simply be accepting the change as if the IAU were an authority instead of a collaboration of experts.

I’m telling you: Don’t start rewriting the textbooks yet.

The original definition was simple. In order for a celestial body to qualify as a planet, it must (1) have sufficient mass to pull it into a relatively round shape and (2) orbit the sun rather than orbit another planet.

The original draft defining planets not only included Pluto, but Ceres, UB313 (aka. “Xena”), and Pluto’s companion Charon. Charon was included because its orbital center of gravity is between it and Pluto, where Earth’s Moon would not qualify because the center of gravity is inside the Earth. The Moon orbits the Earth, Pluto and Charon orbit each other.

Then, on the last day of the Prague conference, a minority of astronomers voted to add one more clarification to the definition. The new criteria requires (3) the celestial object have “cleared the neighborhood around its orbit.” According to this new definition, Pluto is not a planet because its orbit crosses Neptune’s orbit, it is instead a “Dwarf Planet” or “Pluton.”

This new criteria simply doesn’t make any sense. It is vague, inconsistent, and unscientific. The logic would work both ways. If Pluto hasn’t cleared Neptune of its orbit, then doesn’t that mean Neptune, a gas giant 17 times the mass of Earth, is a “Pluton” for crossing paths with Pluto? Does the Earth cease to be a planet whenever an asteroid flies past it? Did Jupiter stop being a planet while the fragments of comet Shoemaker-Levy 9 pummeled it? What about other solar systems? A young solar system can have gas giants larger than Jupiter sharing an orbit with massive amounts of space-debris. It could take millions to billions of years for these enormous celestial bodies to clean up their orbital paths. What happens if astronomers observe a celestial body as meeting this criteria, but then later discover other objects in its orbital path? With our perpetual advances in astronomical observations, we will have objects falling in and out of “Planet” status all the time.

Where are the concrete numbers in this third criteria? There is no ratio of orbital-length to acceptable amount of debris in the orbit for an object to qualify as a planet. What about mass ratios? How much more massive must one body be to another in the same orbit for the smaller object not to count as debris?

This criteria has raised far more questions than it has answered, and the answers to these questions will require such volumes of technical jargon to define them as to only make matters worse. The scientific principle of Occam’s Razor advises minimalism and simplicity in scientific theories. It is the K.I.S.S. (Keep It Simple Silly!) method for scientists, and the IAU’s third criteria completely flunks this principle. It’s as if this were an attempt by the IAU’s academics to make their field so complex as to exclude all but the most pedantic of intellectuals, when they should be opening the field to more amateurs in the interest of popularizing Astronomy.

Of the IAU’s 10,000 members, only 4% were present for the vote, which was cast on the last day of the conference after many members had already left. The vote was essentially hijacked by a group of dynamicists, astronomers who study the motion and gravitational effects of celestial objects, who were offended that planetary geologists had so much influence on the previous week’s definition (source). Galileo must be spinning in his grave at this illogical and highly political decision.

The original definition added three new planets to our solar system, rather than eliminating a heavenly body we’ve accepted as a planet for 76 years—for the simple reason that it is round and orbits the sun. The new definition is confusing, illogical, and will muddy scientific waters at a time when we need to be making science more accessible to the public.

What’s more confusing: 12 Planets with the possibility of finding dozens more in our solar system? Or 8 planets, with 10-20 vaguely defined “Plutons.” Not to mention asteroids, comets, moons, Kuiper-belt, and Oort Cloud objects?

People must realize that this is not a so much a factual as a semantical debate. The English dictionary evolves and adapts to our evolving use of language. There is no reason an informed public cannot have a say in our shared understanding of what constitutes a “planet.” Carl Sagan said, “There are no authorities, at best there are experts.” The 400+ minority of IAU members who voted to demote Pluto are not an authority, and we don’t have to accept their spurious logic simply because of appeals to authority.

Pluto, Charon, Ceres, and UB313 all have sufficient gravity to pull them into a round shape and they do not orbit other planets therefore, they are planets. There are 9,500 other astronomers who were not allowed to vote on this issue because they were not in attendance, making this a clear-cut case of “Tyranny of the minority.” The IAU must reinstate Pluto as a planet immediately before its credibility suffers and future generations of scientists look back on the 2006 conference as the day scientific integrity was abandoned because of intellectual hubris.

The Online Community is in the process of getting organized on this issue. In the meantime, you can sign one of the many online petitions and join the debate:

The science has spoken: Pluto will never be a planet again

“One should not need a teleportation device to decide whether a newly discovered object is a planet.” -Jean-Luc Margot

Practically everyone alive today grew up learning some way of remembering the nine planets of our Solar System in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Beginning in the 1990s, however, two revolutions in astronomy happened all at once: the uncovering of trans-Neptunian objects and the discoveries of worlds around other stars. These discoveries compelled us to rethink our definition of a planet, culminating in the official 2006 definition of “planet” by the International Astronomical Union (IAU). Pluto was out. But with many people unhappy with the IAU’s definition, the story doesn’t end there.

When we first discovered Pluto, it was crazy to think it was anything other than a planet. The asteroid belt was known — thousands of small, rocky bodies that were most definitely distinct from planets — but Pluto was thought to be larger and more massive than even Earth to start. We thought it exerted a significant gravitational tug on Neptune, but those observations turned out to be flawed. We thought it was going to be at least as big as the inner, rocky worlds, but it’s less than half the size of even Mercury. And as the bounty of frozen worlds from the Kuiper belt, the scattered disk and even (perhaps) the Oort cloud have come in, we’ve learned that Pluto isn’t all that special by comparison with the rest of the Solar System. It was just first.

At the same time that we were discovering the first additional Kuiper belt objects, we were also finding the first exoplanets. The first planets we found were the easiest type to find: the largest-mass worlds orbiting close in to their parent stars. As techniques and technology improved with the passage of time, we began to find large numbers of worlds of all different masses at a variety of orbital distances from their stars. These exoplanet solar systems have proved to be vast, varied and rich, showing us that our Solar System is both nothing special and not even necessarily the norm. The diversity of what’s out there is tremendous.

So who gets to be a planet? And who determines it? The IAU’s original, 2006 definition was as follows:

  1. It needs to be in hydrostatic equilibrium, or have enough gravity to pull it into an ellipsoidal shape.
  2. It needs to orbit the Sun and not any other body.
  3. And it needs to clear its orbit of any planetesimals or planetary competitors.

As you can see, it’s problematic from the start. For one, it doesn’t define “planet” for any star system other than our own. For another, “clearing its orbit” seems pretty subjective and dependent on what else is out there. (If you were to place Jupiter too distant from the Sun, it would fail to clear its orbit would it therefore stop being a planet?) And even if you replaced “the Sun” with “its parent star,” it isn’t like we can measure exoplanetary systems well enough to tell whether their orbits are cleared or not. The definition isn’t precise enough.

On the other hand, planetary scientists have proposed a geophysical definition for a planet:

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 parameter.

But this poses a set of problems, too. Large moons (like ours) and asteroids would become planets. Charon, Pluto’s moon, would be a planet. In fact, over 100 known objects in our Solar System alone would become planets. In our efforts to include Pluto, we include every non-stellar object more massive than about 0.01% of Earth’s mass. The big problem is it’s far too inclusive.

Solar systems come in huge varieties. The recently discovered system around TRAPPIST-1 looks more like Jupiter and its moons than like our Sun and its revolving worlds, but these seven Earth-sized bodies should definitely be planets. They meet the geophysical definition, but that’s only the starting point. They also — and you may feel strongly or less-strongly about some of these — meet the following requirements:

  • They orbit their parent star.
  • They dominate their orbits in terms of mass and orbital distance.
  • They would clear out any debris in their orbit in well under 0.1 billion years.
  • And their orbits, barring any outside influences, will be stable as long as their star exists.

What’s perhaps most remarkable is that we can make a simple, mathematical relationship between a world’s mass and its orbital distance that can be scaled and applied to any star. If you’re above these lines, you’re a planet if you’re below it, you’re not. Note that even the most massive dwarf planets would have to be closer to the Sun than Mercury is to reach planetary status. Note by how fantastically much each of our eight planets meets these criteria… and by how much all others miss it. And note that if you replaced the Earth with the Moon, it would barely make it as a planet.

When it comes to planetary status, geophysics isn’t enough. In astronomy, the three rules of real estate also apply: location, location, location. There’s something very meaningful about our place in the Solar System that makes Earth a planet and Pluto not-a-planet. If we’re being honest about our Solar System and the number of planets within it, there are very clearly eight objects that are different from all the others.

There’s a limit to how far you can move Earth away before we become a dwarf planet or even a rogue (or orphaned, i.e., star-less) planet, and it’s important to have a real definition that means something wherever we look.

After all, the next decade should teach us whether there’s a larger-than-Earth mass out in the distant Solar System: what’s been dubbed Planet Nine. If this world does exist, we should be able to determine its mass and its orbital parameters. It will be an interesting object, a tremendous discovery and a fascinating world whether it makes it as a planet or not. But will it meet not just the geophysical but the astronomical criteria for being a planet? That’s a scientific question that should have a right (and wrong) answer. It’s up to us to draw the planetary line correctly, unswayed by our own biases and opinions.

Science Behind the Fiction: How Pluto made the solar system bigger

Thirteen years ago, today, Pluto received a demotion. Nothing had changed about the icy world itself, but our understanding of the solar system had grown and new questions had arisen. This amounted to one of the most drastic changes in the public understanding of our solar system. And it all ties back to a little trans-neputunian world called Eris.

Why Pluto was Reclassified

Discovered in 2005, astronomers at first believed Eris to be larger than Pluto, sparking debate about whether or not it should be named as the tenth planet. Astronomers were forced to take a closer look at what it means to be a planet, as opposed to something else. Eris is positioned in the Kuiper Belt, a region of space containing icy remnants from the early formation of the solar system.

When the sun was young,and the solar system little more than a cloud of dust and energy, matter pulled together under the force of gravity, forming planets, moons, and smaller objects--the solar system as we know it--but beyond the orbit of Neptune, matter was far enough away to avoid capture and accretion.

Astronomers believe this region of space may be home to more than a hundred objects similar to Pluto. Eris is one of these. It is so far distant, it takes 561 years to orbit the sun. All of this called into question the way we define and classify the objects in our stellar neighborhood.

The International Astronomical Union had a decision to make. Do we add a new planet, potentially opening the door to dozens or hundreds more, or do we create a new classification and lose Pluto in the process?

In 2006, they landed on reclassification and the ripples that decision, sent through the astronomical community, and the world, are still being felt.

The decision was made that, in order for a body to attain planetary status, it had to meet certain criteria.

What Makes up a Planet?

First, it must orbit the sun. Simple enough.

Second, it must have sufficient mass to pull itself into a spheroid shape.

Third, it must not be a satellite of any other object. This one is important. If planetary status were defined by the previous two criteria alone, there would be a great many planets to add to our model. Our own moon meets those criteria. Many of the moons orbiting the gas giants meet those criteria and are, in fact, more massive and more complex than some of the existing planets.

Finally, it must gravitationally dominate its local neighborhood.

These last two rules are where Pluto hit a snag. It’s relationship to it’s largest moon, Charon, is such that they orbit one another in a binary system, around a common point outside the mass of Pluto. In a sense, this means that while Charon is a satellite of Pluto, Pluto is also a satellite of Charon. It also isn’t considered to have cleared its region in the same way other planets have. This is something of a point of contention as no planet has truly “cleared” its neighborhood. Objects come into proximity and into contact with planets all the time. Anyone who has seen a shooting star can attest to that. And if you’re still in doubt, just ask the dinosaurs.

What it really comes down to is the realization that our solar system is much more complex than we previously imagined and we’re just not very good at defining and classifying things which don’t have clear, demonstrable boundaries.

What was, perhaps, the most surprising discovery to come out of that 2006 meeting of the IAU was not the reclassification of Pluto but the huge public outcry. People, it seems, love Pluto, and they considered it a shock and a personal insult to slight it in this way. This sentiment has been solidified by the findings of the New Horizons mission which visited the far-distant world, returning stunning photos and a whole host of new information.

This raucous public conversation and controversy about the status of Pluto among its celestial companions hasn’t been all bad. It’s led to a period of high public interest in astronomy. In one of the greatest examples of the old adage, “no publicity is bad publicity,” the public at large has become engaged in the exploration and understanding of the solar system in a way that hasn’t been seen in decades.

While the outrage stems from a sense that our solar system has, in some ways, become smaller, the opposite is actually true. Where before, we sat perched on the third of nine planets, now we are part of a richer and more complex system. One which includes five dwarf planets and, if our models are correct, many more to come.

At current, Pluto is the largest of five known dwarf-planets, each of them interesting in their own ways and worthy of study and public awareness. Pluto was once beloved because it proved there was more to discover. There was more out there to see and understand. And it’s new position doubles down on that notion. Instead of being the newest and smallest of the known worlds, it is now the poster-child for a whole new type of world.

Let’s start with the King. Not much was known about Pluto before the New Horizons mission, but since its arrival at the near-edge of the solar system, our understanding has grown drastically. It’s orbit is highly erratic. Pluto orbits at odds with the celestial plane and actually intersects the orbit of Neptune, sometimes bringing it in closer to the sun than the eighth planet.

Pluto's atmosphere as seen from New Horizons. Source: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

That, in and of itself, makes Pluto unique but the truly stunning revelations came when we got up close and personal.

New Horizons revealed a world both beautiful and full of activity.

It’s most apparent feature is a heart-shaped glacier the size of Texas and Oklahoma on its face.

It addition to this incredible geological feature, it has areas free of impact craters suggesting geological activity and fairly young surface.

West of the heart-shaped region is an area called Cthulhu Macula which houses mountains rivaling the Rockies where blood-red methane snow falls. It’s an environment so alien even Lovecraft might have fallen into madness at the sight of it. Whatever classification we ultimately bestow upon Pluto, there’s no denying its splendor.

Eris is nearly the twin of Pluto in size. Named for the Greek god of discord--a fitting name considering all the trouble it stirred up--Eris also lies in the Kuiper Belt. It is one of the most reflective bodies in the solar system, bouncing back nearly 96% of the light that reaches it. It is believed it has an atmosphere of nitrogen and methane only a millimeter thick which fluctuates between solid and gaseous states as the dwarf-planet’s orbit takes it closer to and farther away from the sun.

At the time of its discovery, there was a possibility it would become the tenth planet. It was not given that honor, but was responsible for the new designation, of which Pluto became a part.

Haumea, named for the Hawaiian goddess of fertility, is approximately 385 miles in radius, roughly one forteenth the size of Earth. It orbits at a distance of 43 AU (the average distance from the sun to Earth) and takes 285 years to complete an orbit.

Haumea and its moons. Source: NASA

Haumea is unique among the dwarf planets, owing to its shape. Instead of being spherical, it has a shape more akin to a football. This is a result of its fast rotation. It revolves on its own axis every for hours. The outward force generated by the spin is at war with its own gravity, causing it to splay out like a child being spun by the arms. It’s furious spin is believed to be the result of an ancient impact with another object, one that also created its moons. It is also the first known Kuiper object which has rings.

Makemake (mah-kee-mah-kee), like Eris, was discovered in 2005 and is named for the Rapa Nui god of fertility. Like the rest of the dwarf-planets listed so far, Makemake orbits in the Kuiper Belt taking more thatn 300 years to complete an orbit. It is fairly reflective but has a moon black as charcoal.

Ceres is the final officially recognized dwarf-planet to-date. It has the honor of being the first dwarf-planet discovered, being first observed in 1801. It differs from the others of its classification in being the only one which lies within the inner solar system.

Ceres as seen by the Dawn spacecraft. Source: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Ceres orbits between Mars and Jupiter, in the asteroid belt. It was, for a long time, considered to be the largest asteroid there, making up approximately a quarter of all the matter in the belt. Still, it is small. Pluto is fourteen times as massive. It has no atmosphere or moons. It was, however, the first dwarf-planet to be directly studied. The Dawn mission reached it in 2015.

What’s most startling is the relative obscurity of Ceres in the more than two centuries since it was first discovered. This likely owes to our classification of things, something the demotion of Pluto changed.

While reclassifying Pluto caused waves the world over, it shined a spotlight on these other worlds, something which might not have happened otherwise, and that’s a worthwhile legacy. Pro-Pluto proponents, however, still have hope. The debate about the status of Pluto and the rest of the dwarf-planets is still ongoing. Many within the astronomical community have challenged the classification and believe planetary status should be restored to Pluto and expanded to others.

14 Replies to &ldquoSorry Pluto, Eris is Bigger&rdquo

Both Pluto and Eris should be considered full fledged planets, as should any objects orbiting the sun (or any other star) that are not stars themselves and have achieved hydrostatic equilibrium. The fact that Eris is more massive than Pluto has absolutely no bearing on this. The IAU demotion was a sloppy and controversial decision by four percent of its membership, most of whom were not even planetary scientists. We should be broadening, not narrowing, our conception of what a planet is.

Pluto is never going to be a real planet. SAD

Yes it is. And maybe Eris, too.

I’m fine with Eris becoming a planet.

Just as long as Pluto is, too.

Nine planets! And I don’t mind a tenth at all!

I’d hate to post a fifth comment in a row, but just one more thing: Laurel, I totally agree with you. IAU made a couple mistakes with Pluto:
Something could have knocked Pluto out of orbit. I think that something was Charon, and they got sperical shapes, as well as forming Hydra and Nix! The impact could have also caused Pluto to have an orbit that could allow it to pass Neptune! If it has a bad orbit, why isn’t it a planet? I’ll tell you this: just because Pluto has a bad orbit, doesn’t mean it’s not a planet!

Also, New Horizons was on it’s way. By the time they erased Pluto, it was probably bareley an eighth there! I will never like IAU until they undo their stuff.


I think Pluto should stay under the term dwarf planet. And if Pluto is one, then Eris should be one too! We have at least 10 planets in our Solar System and there is no denying it.

Yes, Eris and Pluto are planemos. A dwarf planet is not a completely separate class of objects, it’s sort-of a planet. Who cares about how it orbits? In other planetary systems, planets several times (up to 8) more massive than Jupiter orbit in much, much more elliptical orbits. At first I did not even agree that a planet needs to be in orbit around the Sun or another star.

Are there extrasolar dwarf planets?

People say not to discriminate against small people, but out in space they are discriminating against small planets. Pluto is more than Micky Mouse’s pet dog. It is also the should-be ninth planet in our solar system. Our solar system includes four rocky planets and four gas giants. Pluto’s rock-ice composistion and unusual orbit sets it apart from both families, but it shares some of theses traits with the Kuiper Belt objects. Therefore, astronomers dive in a consistent heated battle to define whether or not Pluto is a planet or part of the Kuiper Belt.

Pluto has recently been the subject of debate between those who say it should be counted among the Kuiper Belt objects, and those who don’t want to diminish Pluto’s status as the ninth planet. That debate boils down to what is a planet and what is not, a straightforward concept with no real definition. Yes, Pluto doesn’t fit one of the priorities to be a planet. This one difference is that Pluto doesn’t have a clear neighborhood around its orbit and is not a satellite. Because of that, Pluto is now a “dwarf planet,” one that orbits the Sun but that has insufficient mass to “gravitationally dominate” its region of the solar system—that is, enough mass to sweep away other stuff orbiting there. Originally classified as a planet, Pluto is now considered the largest member of a distinct population called the Kuiper Belt. Still trying to refine the definision, the task is growing more difficult as scientists discover the increasing number of weird worlds found circling other stars. And even worse, those little bodies that don’t qualify as planets will now be called plutoids or planetoids! Talk about respest.

Both Pluto and Eris should be considered full fledged planets, as should any objects orbiting the sun, that are not stars themselves and have a nealy round shape. The fact that Eris is more massive than Pluto has absolutely no bearing on this. The IAU demotion was a sloppy and controversial decision by four percent of its membership, most of whom were not even planetary scientists. We should be broadening, not narrowing, our conception of what a planet is.

Last year, the ninth planet was demoted because astronomers had a discovered a nearby object, planet-x, now officially named Eris, that was larger than Pluto. But instead of taking the route of accepting Eris into their family, which would have opened membership in the club of planets, astronomers decided to get more picky about what defines a planet. Two years after the controversial decision to take away Pluto’s status as a planet, astronomers are still unable to agree on how to define planet. When they finally came up with something, they quickly made it into a definition.

On August 24th, 2006, scientists redefined a planet without Pluto, after the American Museum of Natural History created a solar system model without Pluto. When thinking about what the definition of an actual planet, and a dwarf-planet would be, astronomers discussed the current definition of a planet and decided that a “planet” is a body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity has a nearly round shape, and (c) has cleared the neighborhood around its orbit. A “dwarf planet” is a 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 has a nearly round shape, (c) has NOT cleared the neighborhood around its orbit, and (d) is NOT a satellite. After a week of debate, the IAU (International Astronomical Union) took Pluto out of planetary status because its orbit crosses Neptune’s and therefore fails one of three planetary requirements. Pluto DOES orbit the sun, is ball-shaped, but is not a satellite and it does not have an isolated orbit.

I realize that Pluto is neither a dull, terrestrial planet or gas giant. It’s mostly ice. It’s smaller than our own Moon, and has an orbit so strange that it spends 20 years of its 248-year revolutionary period inside Neptune’s orbit. It’s tilted at a crazy 17-degree angle and its satellite, Charon, is so large that it’s been called a double planet. We have already kicked Pluto out of out planetary status before it has had one orbit! Why judge in such a hurry? 1930 was only like… five months ago in Pluto time! And instead of My Very Elegant Mother Just Served Us Nine Pizzas, I guess she’ll now have to serve us nachos, noodles or nectarines. I’d rather have nine pizzas.

u no wat, i don’t care wat scientists think, PLUTO SHOULD BE A PLANET.

Yes, Pluto Is A Planet Says NASA Scientist At The Site Of Its Discovery 91 Years Ago This Week

Dwarf planets and moons, illustration. A dwarf planet is a planetary mass object orbiting the Sun . [+] that is not a true planet. They are massive enough for their self-gravities to crush them into spheres, but they have not cleared the neighbourhood of other material around their orbits. Ceres, for example, shares its orbit with other asteroids. All the other dwarf planets so far known are found beyond Neptune, in a region of the Solar System full of debris called the Kuiper belt. Here are the five currently confirmed dwarf planets in the Solar System as of 2018 along with their known natural satellites, or moons. From left to right they are Pluto (with Charon, Hydra, Mix, Kerberos and Styx), Eris (with Dysnomia), Makemake, Ceres, and finally the oddly shaped Haumea (with Hi iaka and Namaka). Haumea is an ellipsoidal shape rather than a sphere, owing to its rapid spin.

Is Pluto a planet? It’s been one of astronomy’s most controversial questions since a meeting of the International Astronomical Union (IAU) in August 2006 voted to downgrade the then-ninth planet to mere “dwarf planet” status.

Not only is the IAU’s definition of a planet 15 years ago roundly ignored by planetary scientists, but the IAU’s use of a vote made science seem arbitrary and political, undermining trust in science itself.

So says Dr. Alan Stern, a planetary scientist who leads NASA’s New Horizons mission that explored the Pluto system in 2015. He was speaking at the “I Heart Pluto Festival 2021,” a virtual program of lectures and events staged by Lowell Observatory in Flagstaff, Arizona—the very sight of Pluto’s discovery on February 18, 1930 by astronomer Clyde Tombaugh.

Stern’s argument against the decision to relate Pluto to “dwarf planet” status boils down to this: it doesn’t make scientific sense.

The IAU relegated Pluto after a flurry of new discoveries of small planets in the outer Solar System—notably Eris in 2005—so the IAU felt that it had to create a tighter, more exclusive definition of a planet:

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  1. It orbits the Sun.
  2. It has enough mass (and therefore gravity) to be round.
  3. It has “cleared the neighborhood” around its orbit.

Pluto doesn’t get tick that last box because it’s influenced by Neptune’s gravity. It also shares its orbit with other objects in the Kuiper Belt.

So Pluto was re-classified as a “dwarf planet” to sit alongside Eris, Ceres, Haumea and Makemake.

Stern thinks that definition of a planet is poorly worded. “The IAU’s definition was created by non-experts—astronomers—who study stars, galaxies and black holes,” he said. “They botched it.”

Enhanced color global view of Pluto, taken when NASA’s New Horizons spacecraft was 280,000 miles . [+] (450,000 kilometers) away.

He thinks the IAU overacted because they were horrified by the idea that there could be hundreds of small planets beyond the orbit of Neptune in the Kuiper Belt. “The purpose of the IAU in creating this definition was to limit the number of planets in our Solar Systems so that school kids wouldn’t have to memorize long lists of planets,” he said. “Astronomers became afraid of astronomically large numbers.”

That’s a shame because one of the revolutions in planetary science in the last 40 years has been the discovery that the Kuiper Belt—that “third zone” in the Solar System beyond the orbit of Neptune—is busy with comets, planetesimals and small planets like Pluto. “They now outnumber the terrestrial and gas planets and are expected to number in the hundreds when surveys are complete,” said Stern.

He also makes the point that the Solar System is littered with asteroids to the extent that no celestial body has “cleared the neighborhood” around its orbit.

It’s why planetary researchers ignore the IAU’s definition of a planet in favour of a geophysical definition that’s completely agnostic to the total number of planets in the Solar System:

  1. It has enough mass (and therefore gravity) to be round.
  2. It has insufficient mass to undergo nuclear fusion in its interior.

That way, Stern says, Pluto easily qualifies as a planet—as do all “dwarf planets.”

Members of the International Astronomic Union (IAU), vote on a resolution for planet definition 24 . [+] August 2006 in Prague during the closing ceremony of the 26th General Assembly of the IAU. Pluto today lost its seven-decade status as the ninth and outermost planet of the solar system, the world's top astrononomical body decided. However, the solar system may soon be home to a dozen planets, with three new additions to the club and more to come, if astronomers meeting in the Czech capital approve a new planetary definition, the conference organizer said today. AFP PHOTO MICHAL CIZEK (Photo credit should read MICHAL CIZEK/AFP via Getty Images)

However, Stern also accused the IAU of harming science itself when it publicly voted to relegate Pluto in 2006. “Voting is a terrible mechanism of doing science,” he said. “We don’t vote on the theory of relativity. We don’t vote on quantum mechanics. The image of the IAU taking a vote was the single most damaging pedagogical event in science in probably a century, because to many people it was easy to reach the conclusion that science is arbitrary or political, which it is not.”

The argument about Pluto is about semantics. After all, where astronomers draw the line between planets, dwarf planets, planetoids and moons is essentially arbitrary and makes zero difference to reality. Even Stern’s keynote—provocatively titled “Why Pluto is a Planet, The Embarrassment of the IAU, and Why They Had It Coming” is a callback to “How I Killed Pluto And Why It Had It Coming” book by Mike Brown, one of the discoverers of Eris.

Stern’s argument is merely that science should be agnostic. “There are countless stars and there are countless planets—and who cares? It’s just the data,” he said. “We have to give up the old 20th century notion that we need to remember the names of all of them—this is big science and there is a lot of data. We as scientists are reductionists and we want to have classifications systems, but we don’t require memorization—that’s stamp-collecting.”

What objects has Pluto "failed to clear", and why has it failed to do so?

Is the issue that it’s so far from the sun and has such a massive orbit that it has not yet had time to clear all the asteroids and clutter that share a similar orbit? Given more time, is it likely inevitable that Pluto will become a planet? How many objects (roughly or precisely) does it have left to clear? Are they numbered/named? Is Pluto large enough to do so and simply hasn't, or is Pluto lacking some attribute (size/density/mass) that is causing it to fail to clear its orbit? What's the largest object that it shares orbit with?

There are many plutinos in about the same orbit as Pluto. Such as Orcus and Lempo. Pluto is the largest of them, but added all together the rest are over 12 times more mass. Pluto can't clear them out, because they are in resonance with Neptune, and therefore with Pluto.

"Orcus is at aphelion when Pluto is at perihelion and vice versa"

So that means they're orbiting in the opposite direction? So unless there's an infinitesimally unlikely planet to planet collision, the odds of them "getting close" while orbiting and absorbing each other is nonexistent.

"they are in resonance with Neptune"

I'm unclear what that means. does it mean that they're on a different orbital path from Pluto?

Pluto is itself a gravitational "slave" of Neptune, locked into an orbital resonance with the giant planet. "Clearing the neighbourhood" is not an absolute thing, a planet such as Neptune can have small objects in resonant orbits with it.

But what about an object like Eris, which is in no such orbital resonance? Well there are two ways to look at "clearing the neighbourhood". One is observational. Compare the mass of the candidate planet to the mass of everything else that can come the same distance from the Sun. A planet should outmass all the other stuff combined by a factor of 100 or more. In the cases of Pluto and Eris, the other stuff (even excluding Neptune for Pluto) outmass them at least tenfold.

The second approach is more theoretical. Based on an objects mass and its orbital radius, we can predict whether or not it's likely to clear its neighbourhood. It is true that the larger the orbit the "harder" it is to clear, and that combined with Pluto's small mass means it never stood a chance. If Mercury was only as massive as Pluto it would probably still be a planet in such a close orbit. (In fact Mercury is 25 times Pluto's mass).

In the solar system, whatever measure is used there's a clear divide between planets and dwarf planets, as can be seen in the table linked below. There are no borderline objects. Whether this is generally the case in other planetary systems is not I think known.

There are a ton of dwarf planets out there, so either add them all or it them in a different class, basically.

That third criterion is the subject of some controversy, though:

I'm not asking "why isn't Pluto a planet", the third criterion is what I'm focusing on. I read an article that claims that as of 2016, Earth needs to be reclassified as a dwarf planet according to the third criterion:

The question however is if there's a list of objects that are preventing Pluto from being full planet status, and if so how comprehensive that list is, and WHY it is, fundamentally, that Pluto has failed to clear.

As a side note, of the remaining 50 or so celestial dwarfs, which ones of them are fully qualified with the exception of the third rule? I think Ceres is one of them, no?

How many objects (roughly or precisely) does it have left to clear?

Soter, 2006 had a pretty decent way of examining this in a simple yet clear way: Of all the mass in a candidate planet's orbit, what percentage is part of the planet itself?

If you add up all the material in Earth orbit, you find that 99.999% of it is part of the Earth/Moon.

If you add up all the material in Pluto orbit, you find that just 7% is part of Pluto itself. There are many, many other Kuiper belt objects in the same orbit.

Is the issue that it’s so far from the sun and has such a massive orbit that it has not yet had time to clear all the asteroids and clutter that share a similar orbit?

This is part of the problem, the other part being that Pluto is just very low mass - almost 500x less massive than Earth, and more than 5x less massive than our Moon.

Again from Soter, 2006, let's introduce the concept of "characteristic timescale for clearing": i.e. how long its take to clear 1 - 1/e = 63% of all remaining bodies in the orbit. So after 1 timescale, e -1 = 37% of bodies remain, after 2 timescales, e -2 = 14% remain, after 3 timescales e -3 = 5% remain, etc. This timescale, t , depends on two things:

. where P is the orbital period and M is the mass of the body. We can use Kepler's Third Law to express this in terms of distance from the Sun, D:

So while distance certainly matters for clearing (to the power of 3/2), mass matters a bit more (to the power of 2).

An interesting thought-experiment here: What if, at the beginning of the Solar System, we put Earth out at the Kuiper Belt - would we still call it a planet today? At an orbital distance 39.5 times larger than its current orbit, it would clear its orbit 39.5 3/2 = 248 times slower.

However, using Soter's Equation 1, Earth characteristic clearing timescale at that distance is still only 25 million years, a lot less than the 4.6 billion year age of our Solar System. If you flip the experiment around - put Pluto at Earth's orbit - it's characteristic timescale is still about 20 billion years, substantially older than the age of our Solar System, with e -4.6/20 = 79% of objects still left in its orbit by now.

Ultimately, then, it's mostly Pluto's mass to blame here.

Given more time, is it likely inevitable that Pluto will become a planet?

Eventually, yes, but not even close to before the Sun goes white dwarf. Pluto's current characteristic clearing timescale is about 4 trillion years.

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Ah, the Planet Pluto ( Score: 4, Insightful)

I remember it well -- before the anti Pluto is a Planet conspiracy. Good to see it's getting some recognition, rather than more damnation.

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I remember it well -- before the anti Pluto is a Planet conspiracy. Good to see it's getting some recognition, rather than more damnation.

The whole "We changed our mind and decided that Pluto isn't a planet" is bullshit. Just say that Pluto and Eris are both planets and be done with it.

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But you don't have a problem with Ceres no longer being a planet?

Typical orbitist prejudice.

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I have no problem with Ceres being a planet, too.

What is that bickering about calling some rocks planets and not others? Do they get some kind of government pension for being planets like them being some sort of veterans or what's the big deal?

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Re:Ah, the Planet Pluto ( Score: 4, Informative)

Because the definition of what is a planet changed. For no good reason at all.

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By the way, there was a time, when it was the set, as Ceres was discovered in 1801, and Neptune in 1846. Ceres got thrown out, and Neptune was included. And no one was complaining about arbitrarily changing a non-existant definition.

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Except that only Ceres is big enough to have become a spheroid under the pressure of its own gravity. Which is actually a pretty significant feature (unlike the orbit nonsense), and a fairly solid reason for putting something in a separate category from "random rock".

Vesta was actually on the bubble for a while. Despite the big chunk missing from one side, the final decision about whether it would be a dwarf planet or asteroid wasn't made until the Dawn mission gave us a better close-up look.

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The whole "We changed our mind and decided that Pluto isn't a planet" is bullshit. Just say that Pluto and Eris are both planets and be done with it.

Define "planet" in a meaningful, non-arbitrary way that does not include dozens of other bodies not traditionally recognized as planets in our solar system (e.g. Ceres). It's believed the Kuiper belt has hundreds of dwarf planets. You want to promote them all just to not have to give up a mnemonic from childhood?

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Sure. All objects named after the God of The Underworld and radioactive elements Shalt Be Planets.

It's not arbitrary either because I say so.

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Its as arbitrary as declaring Pluto not to be a planet.

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Anything that orbits the Sun directly in a fairly circular orbit is a planet. Why shouldn't Ceres be one?

And with stuff like Wikipedia, who the hell needs to remember something like that? If you really need to do a classification, go for the time of their discovery, i.e. split them up in 3 groups, the "ancient" ones (Mercury, Venus, Mars, Jupiter, Satur), the "modern" ones (Uranus, Ceres, Neptune) and the "new" ones (everything since).

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Yes! Why shouldn't it be a planet too. It costs the same.

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Anything that orbits the Sun directly in a fairly circular orbit is a planet. Why shouldn't Ceres be one?

Do comets count? How "off" of an orbit do you have to be not to count (and yet for Pluto to count).

Where's the big deal in Pluto not being a planet?

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The distinction between comets and asteroids is no longer scientifically valid. By composition, comets and outer Solar System bodies are the same. Comets just happen to have orbits that get so close to the Sun they evaporate water and other ices and create a tail. There are intermediate bodies in the asteroid belt and out to about Saturn that give off just a little outgassing, but not enough to create a full tail. "Dead comets" have comet-like orbits, but no longer have any volatile

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The big deal with Pluto not being a planet is simply that we have to pull together a whole lot of arbitrary definitions to exclude it. Which may turn into a whole different set of nightmares (like, say, "orbital clearing". What about the Trojans? Is Jupiter no planet anymore now? Or do the other objects in the orbit have to have a certain size compared to the "main" body to be considered "negligible"? How much mass compared to the main body may they have? Or do they have to be independent (i.e. not at a Lag

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The big deal with Pluto not being a planet, is that it was discovered by an American, and Americans are butthurt over losing the "credit" for discovering a Planet.

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I don't give a shit who discovered it. I have to admit, until now I didn't even know who discovered it.

I'm not an American (by neither definition). My reason to want to include Pluto (and, for that matter, Ceres) in the list of planets is that it would create a simpler, more elegant definition of planet that is less dependent on future discoveries. With the current definition (especially the "cleared the orbit" bit), planets are just planets so long 'til we find something in their orbit that they haven't cl

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a mnemonic from childhood?

Mary's "Virgin" Excuse Made Joseph Suspect Upstairs Neighbour.

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OMG!! It is supposed to be: Mary's Virgin Excuse Made Joseph Suspect Upstairs Neighbour's PENIS!

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Don't forget Sedna and Quaoar. and Makemake, and Varuna and.

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Ah yes.. Eris. Let us STRIVE over it.

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But. wouldn't damnation be fitting with something named Pluto?

Re:Ah, the Planet Pluto ( Score: 5, Informative)

1) With the discovery of the other clutter that could be considered within Pluto's orbit, it means that any consistent definition of a planet would either not include Pluto, would include Ceres, or would not include Mercury. After some bickering and debate, the guys who run the telescopes decided to start calling Pluto a dwarf planet, and toss Ceres, Eris, and a couple dozen other big rocks into that bucket.

2) 'Kilo' is the metric prefix for 1000, not 1024. There already was confusion between an OS's kilobyte and a storage manufacturer's kilobyte. Kibibyte is a lame hack to try to instill some semblance of binary order in a scenario where marketing will trump all such efforts.

I now return you to your regularly scheduled ranting.

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2) 'Kilo' is the metric prefix for 1000, not 1024. There already was confusion between an OS's kilobyte and a storage manufacturer's kilobyte. Kibibyte is a lame hack to try to instill some semblance of binary order in a scenario where marketing will trump all such efforts.

Some of us remember when storage manufacturers still used the correct definition of kilobytes and megabytes. It has been a while though.

I now return you to your regularly scheduled ranting.

Thank you, you are most considerate.:^)

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Some of us remember when storage manufacturers still used the correct definition of kilobytes and megabytes. It has been a while though.

Do you mean floppy disk manufacturers, who thought that a megabyte = 1000*1024?

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a kilobyte means 1000 bytes. A kibi means 1024 bytes.
Since binary is powers of 2., anyone who actually understand computers understand why kibi byte is more accurate and proper for the industry.

". used the correct definition of kilobytes and megabytes"
No, it wan't correct, they where wrong Since it was how you used it when you learned it., you are emotional unable to come to terms with the accurate version.

And the name kibi is the result of decades of confusion, and concern that is old then the PC.

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a kilobyte means 1000 bytes.

That depends on what you think "means" means.

If I told a room full of people with a background in IT that my file was exactly one kilobyte, I'm pretty sure the vast majority would take me to mean, sans further information, 1024 bytes.Yes, kibibyte is unambiguous. But in most circumstances it's not that helpful to start throwing around obscure terms for the sake of avoiding the slim possibility of misinterpretation.

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But in most circumstances it's not that helpful to start throwing around obscure terms for the sake of avoiding the slim possibility of misinterpretation.

"Slim possibility"? Seriously? Some hardware types use the 1024 definition, while others use the 1000 definition. When talking about data transfer speed and other contexts "kilo" means 1000. (Bits, despite being the ultimate binary unit, seem to come in 1000s, while groups of 8 of them come in 1024s -- why?) Some software and OSes use 1024 (e.g. Windows) others use 1000 (e.g. many commands in Linux).

Yes, it's possible to navigate all these conflicting standards to have a general sense of when the pr

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But if you asked those same people how big one second of CD music (44.1 kHz, 16 bits/sample) is how many would answer 88.2 kB instead of

86.13 kB? And how long does it take to transfer 100 MB over a 100 Mbit Ethernet connection, excluding overhead? Hint: If you answer 8 seconds, you're off by about 0.39 seconds. Really if you're on such a low level that the distinction matters, most people in IT would get it wrong. Personally I find the abbreviations useful for clarity, but I refuse to use the silly names.

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Some of us remember when storage manufacturers still used the correct definition of kilobytes and megabytes.

The earliest mass storage devices all used powers of 10 definitions, just like hard drives do today. With very few exceptions that was the consistent approach up until the introduction of the floppy disk. When 8" floppies hit the market, IBM stuck with powers of 10, but DEC began using powers of two. When 5.25" floppies showed up all of the manufacturers -- including IBM -- had shifted to powers of two. This made sense because they all had sector sizes that were powers of two.

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Why is it so hard for you aspyrons to understand that the meaning of a word is often dependent on context?

In a decimal context, kilo means 1000. In a binary context, it means 1024. Most of the people that pretend to have difficulty understanding this are actually making money from their 'confusion' - what's your excuse?

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Why is it so hard for you aspyrons to understand that the meaning of a word is often dependent on context?

Well, maybe because almost all the international standards organizations actually agree that there's a single meaning now (even though they disagreed in the past).

In a decimal context, kilo means 1000. In a binary context, it means 1024. Most of the people that pretend to have difficulty understanding this are actually making money from their 'confusion' - what's your excuse?

Look, what the GP said was factually accurate:

the IEEE, ISO and SI standards all agree that kilobyte means 1000 bytes, and megabyte means 1000000 bytes.

The IEC adopted these in 1998 [], leading to full adoption by the IEEE in 2005 []. SI explicitly defines [] kilo ONLY to mean 1000, and though bytes are not technically SI units, they regard any other use of the prefixes as incorrect.

The only large body that has endorsed the use of your system in the past de

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You appear to believe that argument from authority trumps sense. You have it backwards.

First off, I was merely pointing out that GP's statements were factually accurate, and therefore did not deserve ridicule. I said you have the choice to ignore those recommendations by standards organizations if you want. Go ahead. But if you want to argue from a system of logic rather than authority, you may want to reconsider your methods.

Secondly, you have it backwards [] and believe in some mythical authority that never was consistent. If you actually were correct about 1024 being used in ALL cases o

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Your claim that the GPs statement was "factually correct" and your acknowledgement that standards committees are not actually authoritative contradict each other.

The link you posted is actually not that bad an essay on the subject, although I disagree with his conclusions at least he's mostly accurate and aboveboard on his logic.

But you are completely misunderstanding me if you think I am appealing to any nonexistent authority or denying that people use these terms in confusing and incorrect ways on a regul

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You may have a different opinion on those issues and you have a right to that, but you dont have a right to force me to agree.

Absolutely. I acknowledged that in both of my replies to you. My main beef was mainly with the lack of respect and civility -- you want to disagree? Fine. But in doing so, you accused GP of being like hardware manufacturers who deliberately sought to confuse people, and implicitly dismissed the citations of major international standards organizations who advocate the GP's position. You wanna have a different opinion? Fine. But there's no reason to go around insulting people, particularly when they ci

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I think if you'll go back and read the message I initially replied to, as I have just done, you will find that the incivility started there, and I simply replied in kind. He stated without reservation that those using these prefixes intending their binary meaning simply wrong, and cited the busy-bodies as if that were proof of the contention.

If my reply was rude, so was that post, because I did nothing but mirror it back.

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They still do use the correct definition. Some OSes (windows in particular) do not.

And some memory manufacturers, and some processor manufacturers, and some integrated peripheral manufacturers, etc.

Let me know where 65.536 kilobit RAM or ROM in an 8.192k x 8 bit format is advertised. I am also in the market for a DMA controller which supports a 65.536 kilobyte address space.

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the guys who run the telescopes decided to start calling Pluto a dwarf planet

Some guys decided to start calling it a Dwarf Planet, after pretty much everyone else attending the IAU had gone home. They conspired to hold a meeting, without a full quorum and voted these BS standards into place. As disgusting a fixing of science as any effing millionaire/billionaire trying to rewrite school textbooks with whatever they personally would rather the youth of the nation end up spouting.

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Well, that's a complete lie.

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Well, that's a complete lie.

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and toss Ceres, Eris, and a couple dozen other big rocks

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Pluto is a fucking planet. All the morons who herpderp about it not meeting the "requirements" for being a planet need to STFU. Any "requirements" are arbitrarily-defined. Pluto was a planet for both the common and technical definitions for quite some time. To later redefine the already arbitrary term is absurd. If you don't like the term planet, make a new term. Don't change an existing term that has widespread common and technical use, has been used in publications, etc. All you do is create ambiguity with regards to what definition someone means when they use the term. The same shit goes for "kibibytes" - you don't have to like kilobytes being 1024 bytes, but you do have to accept it. Adding "kibibytes" just creates confusion where there was none before.

Correct, the only designation of planet that is questionable is for Earth. That's just a big rock littered with assholes.

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First off, Pluto was originally called a planet back before all of the objects that are in the same orbit as Pluto were spotted, thus under the definition that a planet must clear its orbit fails. Second if kilobytes are so clear and unambiguous, why do hard drive manufacturers consider them 1000 bytes when all computer scientists and programmers consider them 1024? []

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kilo = 1000. From before computer existed. You may not have realized it, but 1000x1024 produces a completely different number then 1024x1024. I know, shocking.
So to say a kilo is 1024 in the computer industry is inaccurate and misleading.
What we need was a name for 1024, which we now have.

Are you seriously saying we should re-define the metric system?

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Some people know that human language is context sensitive and adjust their expectations of meaning conforming to context. WTF is wrong with KB meaning 1024 bytes? The only problem was hard disk manufacturers and their BS propaganda. No one else uses their definition.

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The only problem was hard disk manufacturers and their BS propaganda. No one else uses their definition.

Well, only them and just about every international standards body that actually defines units, including engineering and electronics bodies (e.g. IEEE, JEDEC still allows something like the old 1024 standard, but notes it is deprecated).

Also, various other hardware manufacturers, various software (e.g. many Linux commands), data transfer rates and other things measured in bits rather than bytes, etc., etc.

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WTF is wrong with KB meaning 1024 bytes?

If it were just KB, that would only be somewhat annoying and confusing, like US vs imperial pints.

But when you introduce binary MB and GB they all have to be mixed, and it becomes absolutely infuriating. It makes doing the math to figure out how much stuff will fit on a drive almost as hard as using Roman numerals.

You're basically changing the radix of your numbers depending on their magnitude, for no good reason. (Disk drives have never had any capacity factor physically based on any power of two.) That's

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Pluto IS a planet. By the very definition of planet, deriving from the Greek aster planetes, meaning "wandering star". And it is about as much a wandering star as any other planet.

So either it is a planet or none of the other planets it a planet. Make your choice.

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In fact, actual astronomers refer to all the solid objects that orbit the Sun as "planets". The come in three sizes: major planet, dwarf planet, and minor planet. The IAU Minor Planet Center ( http://www.minorplanetcenter.n. [] ) tracks all those things otherwise known as "asteroids".

The exact dividing lines are:

Major Planet - Round, and massive enough to have "cleared" it's orbit of other large object (it's the dominant mass in it's orbital region)
Dwarf Planet - Round, but has not cleared it's orbit, thus

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It seems to me there should be a fourth category: gas giants. They are considered planets, but there's more differences between Earth and Uranus than there are between Mars and Pluto.

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It seems to me there should be a fourth category: gas giants. They are considered planets, but there's more differences between Earth and Uranus than there are between Mars and Pluto.

To add to the confusion, Uranus and Neptune are sometimes considered "ice giants," since their composition is so significantly different than Jupiter and Saturn.

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Sometimes, a definition really loses its meaning if applied too literally.

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Ok, you win with Sun and Moon. Though I'd say the movement of an object has to be observable within sensible time spans, i.e. stars don't really "move" with respect to a human lifetime.

Aside of that I'd have to concede. But the current definition of planet is not useful either, since "clearing the orbit" is a term that has been applied very arbitrarily. Or, to quote Stern, leader of the New Horizon Mission, "If Neptune had cleared its zone, Pluto wasn't there". Add some Trojans and NEAs and Jupiter and even

Bogus claim ( Score: 2)

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Actually, Uranus is, barely, visible to the naked eye. But most people avoided looking at it, for obvious reasons.

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So the experts need to STFU so a non expert like yourself can feel good about their childhood? You are the one who needs to STFU.

"Pluto was a planet for both the common and technical definitions for quite some time."
What definition? Pluto was call a planet when anything going around the sun was a planet which was fine/. Now that we have learned a lot more it turns out that was a poor way to determine what a planet is.

Now there are specific requirement as to what a planet is, if it turns out the Pluto meets

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So the experts need to STFU so a non expert like yourself can feel good about their childhood? You are the one who needs to STFU.

"Pluto was a planet for both the common and technical definitions for quite some time."
What definition? Pluto was call a planet when anything going around the sun was a planet which was fine/. Now that we have learned a lot more it turns out that was a poor way to determine what a planet is.

Now there are specific requirement as to what a planet is, if it turns out the Pluto meets those requirements then t will be a planet.

" and technical use"
except it didn't. It was a useless term.

Kilo equaled a thousand before there where computers. the Computer industry incorrectly co=opted the name, and that was fixed in 1998.
kibibytes only makes an accurate definition.
I'm sorry you are too stupid to understand logical changes, and corrected definitions based on new data.
Really, nothing should change form how you learned it the first time, right?

^^^ This is just how I would react if I was a Pluto denier/terrorist.

Re:Ah, the Planet Pluto ( Score: 4, Insightful)

If you believe there's some pedantic reason to keep Pluto as a planet, I have to ask whether you hold the same views regarding Ceres.

Ceres was "a planet for both the common and technical definitions for quite some time".

The circumstances surrounding demotion of Ceres and Pluto are rather similar. The timeframe either of the two were considered planets is also similar.

Now, what I find more interesting BOTH for this issue of Eris and Pluto and the argument over Planet classification is to look at MASS instead of diameter:

Look at this chart of bodies in our Solar System ranked by mass in a logarithmic chart. The eight planets unambiguously rank as the largest bodies. Eris still is more massive than Pluto. And all the dwarf planets are outranked by several moons.

Yes definitions are arbitrary. But the eight planets stand apart. It does make sense to align definitions to match such. In any case, the definitions OUGHT to be consistent. What criteria other than inertia of publications would you prefer that keeps Pluto IN yet leaves Ceres OUT?

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In any case, the definitions OUGHT to be consistent. What criteria other than inertia of publications would you prefer that keeps Pluto IN yet leaves Ceres OUT?

The whole argument is retarded because it can't be extended to other star systems (many which don't have the nice structure of our Solar System). Currently, we have a naming scheme with "planets", "dwarf planets", and "exoplanets", yet only one of these three groups actually are planets. Please continue to lecture us on "consistency".