planetary classes

Did the letter classification scheme of planets come from Vulcan, as in Minshara for Class M?

 

I'm an old timer TOS fan, way before "Minshara" came into the picture. Alls I ever knew was Class M, no explanation given. But way back when I was a kid...

Why M? Only thing I could think of was M being smack in the middle of the alphabet. Class M were the planets just right for human life.

Like some kind of Goldilocks thing, I thought the 26 letter alphabet was the gamut of planets. Class A planets were way too cold, Class Z planets were way too hot, but Class M planets were just right (smack in the middle).

Arbitrary? Probably. But at least I didn't invent some Minshara planets to explain the "M".

 

There haven't been that many in the episodes. I can recall:
Class D planetoids - rocky, no atmosphere, minor planets (presumably like Pluto)
Class K planets breathable but uninhabitable due to temperature extremes
Class ? What was the Demon planet again? Was it Y?
Class G - I might have dreamed this one but I think it was a gas giant.

I think some non-canon sources have tried to map out the classifications. Has one ever been formally adopted?

 

Yeah. I like to think that "Class-M" and "Minshara-class" just happen to both start with the letter M.

I'm not sure that temperature is the main qualifier of what class of planet one is, but is one of numerous factors in the over all habitability of a given world. Things like Atmosphere composisiton, gravity, exposure to radiation and other features no doubt play a role as well. But I agree that the closer to "M" in the middle are the habitable worlds.

--Alex

 

These are the known classifications:

Class 6 Gas Giant - "Extreme Risk"
Class 7 Gas Giant - "Broken Bow"
Class 9 Gas Giant (Q'tahl Class Gas Giant) - "Sleeping Dogs"

Class D Planet - Star Trek II: The Wrath of Khan
Class H Planet - "The Ensigns of Command"
Class J Planet - "Starship Down" (a type of gas giant)
Class K Planet - "I, Mudd"
Class K Planet (Transjovan) - "The Royale"
Class L Planet - "The Chase"
Class M Planet - "The Cage"
Class M Planet, Type IV - "The Bonding"
Class N Planet - "Night Terrors"
Class T Planet - "Good Shepherd" (a type of gas giant)
Class Y Planet - "Demons"

Type 4 asteroid - "Practical Joker"
Type C asteroid - "A Matter of Time"

And, there are types of asteroids from A to N. The type is based on size. ("Metamorphosis")

And, there are types of atmospheres from H to M. ("Metamorphosis")

I can't make sense of this.

Note: In the Star Trek: Star Charts, planetary classifications are determined by many factors, including the diameter of the planet. Interestingly, there is a gap - between 15,000 and 50,000 diameters - for which there is no classification, and Neptune falls into this range.

 

When I was very young and was watching TOS for the first time, I always thought that M-class planet meant Maa-class planet. Maa = Earth in Finnish. It seemed pretty logical at the time.

 

...Yeah, it took some time to realize that the letter wasn't being translated for our benefit in the subtitles, and was indeed M (rather than E) in the original dialogue as well.

We have heard various attributes (atmosphere composition, surface temperature) associated with certain classification letters, but we have also witnessed contradictions. Class D is appropriate both for the lifeless, airless rock Regula of ST2:TwoK, the large, solid body Weytahn from ENT "Cease Fire", and the ringed, atmosphered planet of VOY "Emanations".

So I'd argue that any individual parameter, such as atmosphere composition or temperature, is irrelevant to the classification. What counts is the end result, the sum total of attributes: M is something you can colonize simply by pitching a tent, K is something that requires airtight domes, and L requires something in between.

D calls for extensive use of technology if one wants to remain there even temporarily - but the moving down the alphabet from M towards A may also denote the decreasing usefulness of the world to the settlers. That is, D, E and F are all impossible to live on unless you live in a bubble and wear a spacesuit when you go out, but F can at least be mined economically, E could be mined if one went to a lot of effort, and there's nothing to mine on D.

Why the scale would also have to go "up" from M, I don't know. Clearly, the higher letters of the alphabet again denote planets that cannot be easily inhabited, but it sounds redundant to have both A and Z to denote a planet maximally difficult to colonize. Perhaps A stands for planets that are impossible to live on but also worthless, whereas Z is for planets that are impossible to live on but full of treasures? That would allow for Y in "Demon", as it did have enriched deuterium for immediately useful starship fuel, and for gas giants J and T both (because the gases involved might be worthless or valuable).

Timo Saloniemi

 

Ooooh, when I heard T'Pol say Minshara, I just KNEW retcon-happy fans would jump on the class-M thing. The idiot who wrote "Federation: the First 150 Years" even states it plainly.

Dammit, not everything has to tie in with everything else! For 30 years it was just an alphabet designation on a scale!

 

^"Not everything has to tie in?" An odd comment, given that the whole point of ENT was to show the origins of the Trek universe we knew. Naturally the intention was that "Minshara-class" would be the designation that eventually got shortened to M-class. I liked it. I liked the idea that something in standard Federation usage originated with the Vulcans instead of everything being Earth-based. ENT did a very good job of breaking free of that "everything is human in origin" assumption and showing that some familiar things originated with other species -- for instance, Vulcans and Andorians having deflector shields and tractor beams before Earth did, Klingons and Vissians having photon(ic) torpedoes first, Xyrillians inventing the holodeck, etc.

And no, we do not know canonically that these classes are just parts of an alphabet scale. That's a fan assumption, but we don't have enough letters canonically specified to know that for sure. Assumptions are not inviolable truths. And of course, even if there is an alphabet scale in the 23rd or 24th century, they could easily have chosen the letter M to represent Earth/Vulcan-like planets because of the established "Minshara-class" usage. That would make perfect sense and it's a bizarre thing to get angry about.

 

Yes, Geoffrey Mandel's Officer's Manual had a list with planet illustrations, I'm not sure if he was the first one.

Of course, "M" could also stand for "Mother (Earth)", indicating a class of planet you'd feel absolutely safe being there.

Bob

 

They should just ask some real world astrophysicists to work on some proper, consistent classifications based on our current planet hunting.

Currently I assume that we would need differing classifications for:

Planets, Planetoids/dwarf planets, asteroids, and satelites.
We'd need gas giants, rocky planets, and ice planets with or without rings.
We'd need geologically active or inactive, strong or weak magnetic field.
We'd need atmospheric composition, atmospheric pressure, and temperature/temperature extremes.
We'd need life or lifeless.

I bet plenty of scientists would work on the classifications for free!

That gives us a fair range of possibilities with enough scope to cover our list. They need to get to grips with a logical progression though. Class M sits in the middle so what should be either side of it? It would make more sense to me if they started with rocky, then gas, then ice with variations on the scale.

So Class A would be very hot, rocky, low atmosphere, low magnetic field, tidally locked, lifeless, close to a star - like Mercury.
Class B would be gas giant, hot, low atmospheric pressure, low magnetic field, tidally locked, lifeless, close to a star.
Class C would be gas giant, hot, high atmospheric pressure, low magnetic field, tidally locked, lifeless, close to a star and so on.

I suppose they could also adjust classification depending on whether a ship could safely pass through the atmosphere.

 

Back in 2006, I posted a thread in this forum that critiqued Star Charts's version of the planetary classification scheme and offered an alternative suggestion based on modern understanding of planetary sciences. It doesn't seem to be on the forum anymore, but fortunately I saved a copy, so I'll repost it here:

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Rethinking STAR CHARTS planet classification?

The other day, I was looking through the planetary classification scheme covered on pp. 22-29 of Star Charts (which is more or less a mix of the conjectural schemes from tie-in publications over the decades and the few letter classifications that have been established canonically), and I came to realize it has some flaws in its assumptions, particularly where gas giant planets are concerned.

I realized this when I discovered it has no classification specifically for Neptune-class planets. Neptune and Uranus are a distinctly different class of planet from Jupiter and Saturn, sometimes called "ice giants," because they have a different internal composition and structure including a greater proportion of water, ammonia and methane in ice and/or liquid form. But there's no class in Star Charts for that kind of planet. Indeed, Class J, the class including Jupiter and Saturn, is the smallest of the four proposed gas-giant types in SC. Class I is called a "Gas Supergiant" and is said to be considerably larger than class J, ranging up to 10 million kilometers, while classes S and T are said to be even more immense, ranging from 10-120 million km -- which doesn't even make sense, since the Sun is only 1.4 million kilometers across!

Also, when planets get as big as Jupiter or bigger, their cores are so compressed that they collapse into degenerate matter (the stuff white dwarfs are made of). So the more mass you pile onto them, the more you compress their cores, and that shrinking cancels out any size increase you'd get from adding more stuff. That means there aren't any gas giants or even brown dwarfs that are significantly bigger in diameter than Jupiter. 140-150,000 km is the biggest that just about any Jovian or brown dwarf is ever going to get. The only exception is if a Jovian is really close to its star, which would heat its atmosphere and cause it to expand.

This brings up the remaining flaw in SC's categorization of gas giants -- it assumes they would all be in the so called "Cold Zone" beyond the ecosphere. But in recent years we've discovered many "hot Jupiters," Jovians orbiting close to their stars, in other star systems, so we now know that Jovians can be found anywhere in a star system, not just in the outer reaches.

And a fellow named David Sudarsky has come up with a classification scheme for extrasolar Jovians as a function of their distance from their primary stars and thus their atmospheric temperatures, which would affect their appearance and composition.

So instead of the four Jovian classes in Star Charts, three of which are physically impossible, we probably need something like six -- one for each of the Sudarsky classes, plus one for Neptune-class ice giants. Since classes U, V, and W are undefined in the book, those could perhaps be used. Unfortunately, we're canonically stuck with Classes H and K being terrestrial planets and Class J being Jovian, so we can't put those six classes together.

Here are some other Star Charts classifications I have thoughts about:

Class A: Geothermal: A young, partially molten rocky planet. Cools to become Class C: Geoinactive, a dead, frozen planet with Pluto and Psi 2000 listed as examples. Now, the problem here is that Pluto is now classed as a dwarf planet, and that bodies like it are composed as much of ice as of rock.

Class B: Geomorteus (huh?): A hot rocky world close to a star, like Mercury -- except said to be "partially molten" on the surface, which Mercury isn't.

Class D: Asteroid/Moon. The problem here is that there should be more than one class of this. There are several distinct types of asteroids, including silicate, carbonaceous, icy/carbonaceous, or a mix. Luna is a mostly rocky moon, while most large moons in the outer system are a mix of rock and ice (indeed, Saturn's moon Mimas is almost entirely made of water ice). Some moons are bigger than some planets, while others would qualify as dwarf planets if they weren't satellites.

Class E through G: all intermediate stages in the cooling process of young worlds that become class K through P. Do we really need three of them?

Class O: Pelagic: a world with water over more than 80% of surface area. This is a reasonable category to have; recent findings suggest that the inward migration of "hot Jupiters" or the presence of a red dwarf companion could send tons of comets into the inner system to bombard the planets, possibly resulting in terrestrial planets with as much as 100 times as much water as Earth. So worlds that are mostly or entirely covered in water are quite possible. Although I'd set the dividing line between M and O somewhat higher, maybe 90%.

Class Q: Variable: Allegedly something that changes "due to eccentric orbit or variable output of star," but its example of the Genesis Planet is pretty iffy and the category is vague. It might make more sense to say that a planet changes from, say, Class L to class P conditions as it moves in its orbit.

Class R: Rogue, a planet expelled from its system like Dakala in ENT: "Rogue Planet." Actually more scientifically credible than it seems. This class might also encompass what are being called "planemos," planetary mass objects that formed independently in deep space. The problem is that the class doesn't distinguish between terrestrial and Jovian rogues.

Now, canonically, only ten letter classifications have been used: Classes D, H, J, K, L, M, N, P, T, and Y. That leaves the rest up for re-evaluation. And some of the canonical ones could have their details tweaked too without violating onscreen material.


So here's my tentative proposal for a revised classification scheme:

A: A young, molten planet or dwarf planet. (Gothos, Excalbia)

B: A moon or dwarf planet with an outer layer of water ice and perhaps a liquid-water mantle, found in the middle portions of a system. (Ceres, Europa)

C: A moon or dwarf with an outer layer of water, methane, ammonia and/or carbon dioxide ice, found in the outer part of a system. (Pluto, Triton)

D: A dry, silicate moon or dwarf planet. (Luna, Regula I)

E, F, G: Maybe make these lifeless rocky planets of varying sizes, from Mercury-sized to Earth-sized to super-Earth-sized.

H: Canonically, the H-class world Tau Cygna V is habitable but subjected to levels of hyperonic radiation that humans can't survive. Perhaps generally this could be a world that's habitable but too irradiated for humanoids.

I: A Neptune-class ice giant.

J: A Jupiter-class (Sudarsky I) gas giant.

K: Canonically, "adaptable with pressure domes." Say, something reasonably close to Earth gravity but lacking a dense or breathable atmosphere.

L: An almost Earthlike world, but with relatively little oxygen in the atmosphere. Essentially what Earth would've been about 400-500 million years ago.

M: Duh.

N: Let's stick with Mandel's idea of making this a Venus-like world, superdense atmosphere. Fits with the earlier classes being distinguished by their thin or oxygen-poor atmospheres.

O: Pelagic, again sticking with Mandel. Actually I'd like to have N and O the other way around for a better progression, but N is already sort of canonical.

P: Glaciated -- essentially the "Snowball Earth" scenario.

Q: Let's call this a carbon planet of the kind that's been conjectured.

R: I'm willing to stick with Mandel's classification for a rogue terrestrial planet.

S: Call this a rogue Jovian or a sub-brown dwarf. Outside of a star system, it would have different properties from any of the Sudarsky classes.

T, U, V, W: Sudarsky classes II-V.

X: Maybe a hyperthermic environment, hotter than the standard boiling point of water but with enough atmospheric pressure to raise that boiling point and allow hyperthermophilic life to exist.

Y: Demon class, as seen in VGR: "Demon."

Z: Let's call it "other."

 

Ok, I found this here: http://phl.upr.edu/library/notes/amassclassificationforbothsolarandextrasolarplanets

It seems to be a scientifically based classification system. I think Christopher is on to something and if we look at adding in sub-categories to include common sci fi issues such as survivability using pressure suits and pressure domes and ship survivability as key points in the subcategories.


Planet Type Mass (Earth Units) Radius (Earth Units)Potential Atmosphere*
Asteroidan 0 - 0.00001 0 - 0.03Asteroidans are small irregular bodies (below the hydrostatic equilibrium) that are not able to hold a stable atmosphere.
Mercurian 0.00001 - 0.1 0.03 - 0.7Mercurians are only able to hold a significant atmospheres in the cold zones beyond the snow line (i.e. Titan).
Subterran 0.1 - 0.5 0.5 - 1.2Subterrans are able to hold a significant atmospheres after the outer edges of the habitable zone (i.e. Mars).
Terran 0.5 - 20.8 - 1.9
Terrans are able to hold a significant atmosphere with liquid water within the habitable zone (i.e. Earth).
Superterran 2 - 10 1.3 - 3.3Superterrans are able to hold dense atmospheres with liquid water within the habitable zone.
Neptunian 10 - 50 2.1 - 5.7Neptunians can have dense atmospheres in the hot zone.
Jovian 50 - 5000 3.5 - 27Jovians can have superdense atmospheres in the hot zone.
* The cold zone is the zone farther from the star after the habitable zone (which includes the snow line), the hot zone is the zone between the star and the habitable zone.

 

I'd argue that by the time of Star Trek, sufficiently many distinct planet types (that is, permutations on the dozens of relevant parameters) would have been discovered to make a letter-based system impractical - there'd be at least a hundred distinct permutations there, and probably a thousand, if we allow something like the mass difference between 0.5 and 1.5 Earths to be a distinction.

It's not as if our heroes would have much use for such categorizing of planets, either. It doesn't appear to reveal anything noteworthy about the geohistory or -future of the worlds, about the odds of life evolving there, of dilithium being there. It's just diversity forced into a format.

Timo Saloniemi

 

But presumably outside that mass range, gravity would be too great or too low to be class M anyway, proceeding on the assumption that a smaller planet's magnetic field would be too weak within the habitable zone to sustain its atmosphere long enough for life to develop. Although having said that, I think Venus' magnetic field is not all that strong presumably its atmosphere is so thick because of all the volcanic activity?

I suppose a smaller planet would be able to maintain an atmosphere if it has a regular enough supply of icy meteorites to restock it but its hard to see that that could be maintained long enough for complex life to develop.

There are probably only so many classifications that occur in nature so other classifications would need to be for unusual planets that require further investigation. If the demon planet is classified as such because its atmosphere and radiation make it dangerous to both ships and personnel even with protection then those should be considerations taken into account in the classification system.

 

It's believed that Earth might be toward the low end of the size range for habitable planets, because smaller planets wouldn't have plate tectonics, which is necessary for recirculating carbon from the atmosphere or something like that. An exception might be a large moon of a Jovian in the habitable zone, where tidal stresses might drive plate tectonics in a smaller world than could otherwise have it. But there are questions about whether such large moons would be possible, except in rare cases of initially independent planets being captured into Jovian orbit.

 

We are discovering new types of planets constantly. Along with those mentioned, astronomers have discovered diamond planets (http://www.ibtimes.com/discovery-diamond-planet-opens-new-rocky-world-847633) and Hot Neptunes (http://www.centauri-dreams.org/?p=1263).

Here is a real world list of planet types - http://en.wikipedia.org/wiki/List_of_planet_types

Like the situation with dinosaurs - where certain types of species will never be discovered because of where they lived, that there may be planet types that we might never discover.

* http://blogs.smithsonianmag.com/din...-editing-will-we-ever-find-all-the-dinosaurs/

 

Back in the good ol' days--a.k.a. the 1970's--I assumed (and as I recall, along with other fans, too) that the "M" in "Class M" stood for "Mars", because the Star Trek Writers/Directors Guide said, in so many words, that "Class M" stands for "Earth-Mars conditions".

From the Star Trek Writers/Directors Guide, series created by Gene Roddenberry, third revision, April 17, 1967:

 

...in as ham-handed a way as possible.

"Reed Alert!!"