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If Pluto isn't a planet, then neither is Earth

It is the lay people who read headlines and ignore details who spout this nonsense. If you are trolling, please stop.

The unwashed masses want to think of planets as the biggest space rocks. But scientists organize things by various properties and characteristics. There is a dividing line between the biggest space rocks that have the properties most people think of as planets, and the smaller space rocks that are still really big but have have different properties.

If all you want in your classification of planet is "a really big space rock" is a planet, then Pluto can be a planet. It is not a scientifically useful classification, but you're not an astronomer so it doesn't matter to you. Feel free to call moons, asteroids, and comets planets as well. People through history have done that, so you wouldn't be alone.

For the astronomers, astrophysicists, and others who actually use the definitions for scientific purposes, the current classification has eight planets (sometimes called major planets), plus updated definitions for dwarf planets, minor planets, and many more classes of objects. Each one of those classifications has different properties. Pluto is classified both as a "minor planet" and a "dwarf planet". If we accepted Pluto's size and properties as a major planet, we'd need to accept about 1000 others as major planets as well. Astronomers could combine both classifications into a single class called "planets" if all they cared about was popularity rather than useful classifications, but it makes more sense to put them into their own classification bucket since they have different properties.

Under the new classification there are currently about a million "minor planets", about 22,000 of those are named. That's up from about 60,000 known minor planets in the year 2000, and about 27,000 known minor planets in 1995. The current estimate is about a billion minor planets in the solar system. Minor planets are further subdivided based on many different properties useful to astronomers and astrophysicists.

Pluto is one of an estimated 10000 large objects that fit the classification of "dwarf planets". The current list of suspected dwarf planets --- astronomers need more data to completely classify them --- is around 1000 objects.

There are already 20000 named asteroids http://www.minorplanetcenter.n...
Chances are whoever you are thinking about already has one.
There are also half a million more asteroids currently waiting for a name so it's not like we're going to run out of opportunities soon.

According to the Minor Planet Center ( http://minorplanetcenter.net/ ) there are 717,000. A planet being anything that orbits the Sun. They come in three sizes, major planet, dwarf planet, and minor planet. There used to be only two sizes, but we added a new one to accommodate recent discoveries.

Major planets are round, and dominate their orbit. Pluto doesn't qualify, because it's orbit crosses Neptune, which is 8,500 times more massive. In fact, Pluto is Neptune's bitch, being locked into a 3:2 orbital resonance with Neptune. There are thus 8 major planets.

Dwarf planets are round, but don't dominate their orbit. There are about half a dozen of them found so far. Roundness matters because they are no longer in their original form. Some combination of radioactive decay, collision heating, and gravity caused heating, separation by density, and other changes.

Minor planets are everything else, not round, and don't dominate their orbit. They may still be in their original form, unaltered. This matters for science, because they preserve the early history of the Solar System.

If you are not a scientist, you can call Pluto whatever you want, a Disney character for all I care. But scientists will create categories that make sense to them, for their own work, and these are what they have come up with.

2014 FE72 has an aphelion distance of 4,275 AU +/- 20%. Since the orbit period is on the order of 280,000 years, and we have observed it for two, we will have to watch it a little longer to pin down the orbit exactly. Perihelion, at 36 AU, was in 1965, so it is still close to the perihelion distance. That's why we were able to find it. It is ~170 km in diameter, depending how light or dark the surface is.

Source: http://www.minorplanetcenter.n...

> Pluto is a planet. The definition of a planet is arbitrary, and always will be.

If you can find an astronomy textbook from the 1830's or early 1840's, it'll list 11 planets...
Mercury
Venus
Earth
Mars
Ceres (discovered 1801)
Pallas (discovered 1802)
Juno (discovered 1804)
Vesta (discovered 1807)
Jupiter
Saturn
Uranus (discovered 1781)

As time went on, more and more asteroids were discovered. Today, there are a few hundred thousand asteroids. To keep the number of planets at a manageable number, the asteroids wwere given their own class. Similarly, there are now almost 1300 http://www.minorplanetcenter.n... known objects in Pluto's vicinity. If you want to think of the solar system having 1300 planets, be my guest.

Scientists occasionally make mistakes, based on incomplete data. When more info becomes available, they correct those mistakes. E.g. they junked the Aether theory http://en.wikipedia.org/wiki/A... after the Michelson-Morley experiment.

There was *ALWAYS* major doubt about Pluto's planetary status. This article from 1934 http://blog.modernmechanix.com... is an example.

> So that Pluto ranks as the largest asteroid,
> rather than the smallest planet;

BTW, it's worse than the article suggested; Pluto is actually less than 1/10th the mass of Titan.

> and the dipshits who insist that a kilobyte is 1000 bytes.

So you think the ancient Greeks were dipshits? And the French who introduced the metric system? The real dipshits are the people who arbitrarily change the meanings of words after thousands of years..

But if you can give me the exact orbital parameters, that'd be great.

Second link in the summary.

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 Ceres and Pluto fall into this category.
Minor Planet - Too small to become round under it's own gravity.

As a note, the stuff that got "cleared" falls into three groups: impacted one of the other planets and got absorbed, kicked entirely out of the Solar System, or kicked into an eccentric orbit but not ejected. That last group is called the "Scattered Disk", and there are around 400 known objects in the category. They are separate from the Kuiper Belt, which is leftovers in the outer Solar System which have not really been moved in their orbits. There are about 1200 objects in the Kuiper Belt, inlcuing Pluto.

Definitions evolve over time. If we use your definition, then there is no size requirements and we have more than 600000 planets
MPC Archive Statistics

Did Comet ISON escape from the solar system ? Too soon to tell, but I would bet it has an even chance of being now unbound.

According to the Minor Planet Center, ISON has (had) a pre-perihelion eccentricity = 0.9999947.

At perihelion, ISON was traveling at about 370 km / sec, and (given that eccentricity) was only about 0.7 m / sec below its escape velocity. Even a small nudge (of a few m / sec) "along track" thus could have enabled it to escape from the solar system forever (or bound it even more tightly), and (given the amount of mass it probably lost) it could have been thrusted by many 100's of m / sec. It's highly unlikely the outgassing thrust was purely at right angles to the direction of motion, so I would rate the probably of escape as ~ 50%.

this is not just knowledge for knowledge's sake. this is part of efforts to observe planetoids and asteroids to determine if there's risk of collision with Earth, determining feasibility of mining asteroids for resources, or even plain and simple adding to data sets observing how planetoids and asteroids interact with space

a lot of basic science isn't about finding groundbreaking stuff all the time. in fact, if you're doing research only looking for the "groundbreaking stuff", you're doing science wrong. much of science is straight observation. and it is USEFUL.

What's so odd about that? We already have Abbott (17023) and Costello (17024) rubbing shoulders with Larry (30440), Curly (30441), Moe (30439) and Shemp (30444). There are Tomhanks (12818) and Megryan (8353) and even a James Bond (9007) and Monty Python (13681).

Bullwinkle may not be an asteroid yet, but his creator Alan Anderson (14158) does.

Apparently, Mr. Galache tried to get it through as fast as possible but unfortunately Mr. Banks passed away too soon.

I hope Mr. Galache does not mind my reposting of his post from http://friends.banksophilia.com/guestbook :

J.L. Galache on July 2, 2013 at 2:06 am said:
Dear Iain,

We never met, and never will, but your words will remain with me forever. Well, until it’s my turn to turn the lights off. And let me be clear that it’s the Sci-Fi words I’ll keep, not the mainstream ones you used to subsidize them. I admit to not having read all your Sci-Fi novels, but I do have a day job, you know?

Speaking of which, my job as an astronomer at the Minor Planet Center allowed me the opportunity to propose that the International Astronomical Union name an asteroid after you. I really did try hard to get it through the bureaucracy as fast as possible, but alas the naming came a fortnight too late. As I say in my article, I’d like to think you would have been amused by this:

http://minorplanetcenter.net/blog/sci-fi-author-iain-m-banks-gets-asteroid-named-after-him/

Dear Adele,

I hope you can accept this humble gift on Iain’s behalf. Even if he is ever forgotten (and he won’t be), his name will remain as that of asteroid Iainbanks, a 6.1 km hunk of rock orbiting our Sun between Mars and Jupiter every 3.94 years.

May it orbit forever.

Yours,

—JL Galache
Astronomer
Minor Planet Center

> Carl Sagan wrote a lot about the Oort cloud. It would be nice if we could get first-hand evidence of it

We have two types of first hand evidence. The first are long period comets, which spend at least 90% of their life at Oort Cloud distances. They are Oort cloud objects that just happened to have their orbit perigee shifted by passing stars, molecular clouds, or galactic tides. They get close enough to the Sun to boil off their ice content, which makes them easy to find, but otherwise they are still members of the Oort cloud, because that is where they spend most of their time.

The other are "Scattered Disk Objects" ( http://www.minorplanetcenter.net/iau/lists/t_centaurs.html ), which if you sort on "Q" (max distance from the Sun) you will see there are three that go beyond 2000 AU, the nominal inner edge of the Oort cloud. All were discovered in the past year or so, so they haven't made it to the textbooks yet.

There isn't an actual dividing line between the Scattered Disk and the Oort cloud, the nominal distance of 2000 AU is just a convention. How the Oort cloud objects got out there is by scattering of Solar nebula planetesimals by the larger planets. The Scattered disk is just objects that didn't get scattered quite as far.

(I don't know where the 5200 number in the summary comes from but IAU's Minor Planet Center knows of only 4803) .

There is a disparity between their summary table (which lists 4803) and the full table of orbital elements of all Apollo's they (the MPC) provide. The latter counts 5203 objects

There are only 2 types of Earth crossing asteroids: Apollos with a semi major axis larger than 1AU and perihelion smaller than Earth's aphelion and Atens with a semi major axis smaller than 1AU and aphelion larger than Earth's perihelion. There are 4803 known Apollo asteroids (I don't know where the 5200 number in the summary comes from but IAU's Minor Planet Center knows of only 4803) and 747 known Atens, so there was a very good chance that the meteorite was an Apollo...

Otherwise, how do you separate people with plans in motion to go there from those who are merely being 'patent trolls' by claiming something and doing nothing with it?

Claims to a particular piece of real estate shouldn't be valid until physical contact has been made with the body in question, at the site in question.

You could have a moderately interesting conversation about how big an area each "touch down marker" ("stake", whatever you call it) covers. Whether it would be simpler to define it as a radius around the "marker". Maybe minor below a certain diameter would only need one stake to secure the whole object.

( I just went off on an excursion to try to find the distribution of minor planet diameters. From http://www.minorplanetcenter.net/iau/plot/OrbEls10.gif I get a distribution of absolute magnitudes, and from http://www.minorplanetcenter.net/iau/lists/Sizes.html I get an approximate converter for absolute magnitude to diameter. Combining the two, I get that the commonest brightness for minor planets is around 16.5, corresponding to a diameter of around 1300-3000 m. So a 10 km sphere around a "marker" would cover most asteroids and a little over 300sq.km of a larger object's surface. Meanwhile, landing accuracy ellipses for landers are already comparable to that, and are getting better. )

Otherwise, how do you separate people with plans in motion to go there from those who are merely being 'patent trolls' by claiming something and doing nothing with it?

Claims to a particular piece of real estate shouldn't be valid until physical contact has been made with the body in question, at the site in question.

You could have a moderately interesting conversation about how big an area each "touch down marker" ("stake", whatever you call it) covers. Whether it would be simpler to define it as a radius around the "marker". Maybe minor below a certain diameter would only need one stake to secure the whole object.

( I just went off on an excursion to try to find the distribution of minor planet diameters. From http://www.minorplanetcenter.net/iau/plot/OrbEls10.gif I get a distribution of absolute magnitudes, and from http://www.minorplanetcenter.net/iau/lists/Sizes.html I get an approximate converter for absolute magnitude to diameter. Combining the two, I get that the commonest brightness for minor planets is around 16.5, corresponding to a diameter of around 1300-3000 m. So a 10 km sphere around a "marker" would cover most asteroids and a little over 300sq.km of a larger object's surface. Meanwhile, landing accuracy ellipses for landers are already comparable to that, and are getting better. )

There have been several known instances of rocks of non-trivial size passing closer to the earth than the geostationary sats, and in some cases inside the GPS sat constellation.

This one missed us by 1 Earth radius.

http://neo.jpl.nasa.gov/cgi-bin/neo_ca?type=NEO&hmax=all&sort=dist&sdir=ASC&tlim=past&dmax=5LD&max_rows=500&action=Display+Table&show=1

http://neo.jpl.nasa.gov/news/news142.html

http://en.wikipedia.org/wiki/List_of_notable_asteroids#Asteroids

Also, wouldn't it be relatively easy to figure out where this thing was headed and find out where it is now?

"relatively easy" for certain values of "easy" starting at "extremely difficult" and extending towards the impossible.

Firstly, the records are pretty sparse ; effectively we've only got two putative measurement points, and each of those has an accuracy of less than a half-degree (the angular size of the sun). IF (and it is a real "if") there exists a possible Keplerian solution for such an object that fits with the records, then that orbit will be quite imprecise precisely because we don't know where the centre of mass of the object was, merely that some of the particles were within the half-degree area of the Sun's disc. Pick your model for where the centre of mass is - I'd probably start by modelling the first estimates for the centre of mass to lay on a circle of a degree in diameter, concentric with the solar disc - work out the range of Keplerian solutions for each pair of possible observations (say, 4 points at each observation, for 16 possible orbits)

Oh, now you've got 16 possible orbits. But that's still "relatively easy".

How close do these orbits approach the Earth? Because that is going to severely affect the amount by which the orbit is perturbed, both going forward and backwards in time. You're going to face this problem every time the orbit approaches that of the Earth. And the Moon. And the rest - the orbit-tracking code that the MPC uses includes the effects of all the planets, satellites and some of the larger asteroids. (MPC - Minor Planets Centre, the clearing house for observations of minor planets, including potential hitters. Oh, they've moved websites : http://minorplanetcenter.net/iau/mpc.html )

It all gets literally chaotic, very rapidly.

The absence of other observations of cometary fragments around this time is strong evidence that there wasn't a close approach by a comet then. It may not have been as widely discussed a topic then as today (walk down the street today and find how many people know what a "Potentially Hazardous Asteroid" is ; you won't find many people who know, or care), but some people certainly knew what the potential of an impact was, in general terms. The 1910 apparition of Halley's comet was accompanied by significant media hysteria about the closeness of the comet to the Earth. I don't think it credible that 22 years previously, not one person put two and two together to report on an unusual coincidence of comets. Having Hyakutake and Hale-Bopp so close together excited noticeable attention a couple of years ago ; imagine actually having two comets extremely close together in time and in the sky, and moving extremely fast (because they're nearby) - how much attention would that have gathered. Remember too, that this was a time when light pollution was much less extensive.

The problem with the definition of an asteroid is that telescopic surveys are not becoming good enough that smaller objects previously not studied are now being spotted, plotted, and designated by the IAU and the Minor Planet Center. The number of asteroids receiving a catalog number has exploded in recent years, to the point that very few are even being named any more. The current number of objects identified is now more than a half million.

It will be interesting to see when that catalog may be "closed" to a new object that don't meet some sort of size criteria, or what will start happening when more objects of man-made origin get mixed into the database. There are several abandoned vehicles (their power cells/solar panels no longer work and are therefore "dead") and stuff like the Apollo 8 3rd Stage engine (which went into solar orbit) that are "out there" and a few "asteroids" that may be some of this space junk. The Saturn V 3rd stage was identified because of the Titanium-Oxide paint on the outsize... something not normally found on "natural" bodies. Human interaction with especially the smaller asteroids is going to really start making a mess of these catalogs too.