[X] My Assistant

[alan]

2003-UB313 is not a great name for a planet -- and in fact, that's not what the discoverers call it. They've been referring to it as Xena -- after the television series about the Greek warrior princess. Xena was popular when the astronomers began their sweep of the sky in 2000.
http://www.cbc.ca/thecurrent/2005/200508/20050802.html

[tty]

If I remember my greek correctly "Xena" translates as "female stranger"

tty

[Bob Shaw]

For all interested in sizes i made 2 little Diagramms...

Nice diagrams!

I always make use of these verbal comparisons too when describing the planets to other people:

The Moon's surface area is the same as Africa
Mare Crisium is about the same size as Scotland
Mars has the same surface area as Earth's land area
Earth would neatly fit inside Jupiter's Great Red Spot

Are there any other, similar, comparisons out there (preferably not ones which use the size of Wales!).

[David]

If real estate doesn't matter and you classify planet vs. non-planet based solely on size and mass (i.e., is it big enough to have pulled itself into a ball), then what about a majority of the moons of the gas giants?  Remember, real estate cannot be a factor in the equation.

Under the classification system that everything massive or large enough to pull itself into a sphere (more or less) is a planet, we have to admit Ceres, Vesta, the Galilean moons of Jupiter, many other Jovian moons, a lot of Saturnian moons, a lot of Uranian and Neptunian moons, plus possibly thousands of KBOs, all into the League of Planets.

I'm not sure the definition of "more or less a sphere" is -- my own criterion would be "can you make a cylindrical projection from it?" But this criterion has its own fuzzy boundaries (with weird moons like Iapetus sliding off the edge of it). But I don't quite see under which definition Vesta is "more or less a sphere"; to my eye, it's definitely "less" and then some. Likewise, there are no Jovian moons other than the Galilaeans that are "more or less" spherical. Five Saturnian moons are "more" spherical, with Iapetus and Mimas being borderline (and the example of Iapetus shows that major irregularity is not incompatible with large size; contrast the nicely rounded, but very small, Enceladus). Four Uranian moons are "more" spherical, with Miranda being borderline, and the rest irregular. Only one Neptunian moon, Triton, is round. But to determine sphericality, you can't just go by diameter or mass. No one would have predicted (or did) how irregular Iapetus actually is. Proteus is larger than Mimas but blockish rather than round. Quite possibly many of these KBOs are also very irregular despite large size. You actually have to observe their disks directly.

Oh, and while it's not usually called a planet, our own Moon would have to be considered a planet, too.

Which would be just, considering that it was one of the original list of planets, in the pre-Copernican systems. The reason for demoting it from planethood was not its size, but the fact that it did not revolve around the Sun.

[TheChemist]

2003-UB313 is not a great name for a planet -- and in fact, that's not what the discoverers call it. They've been referring to it as Xena -- after the television series about the Greek warrior princess. Xena was popular when the astronomers began their sweep of the sky in 2000.

If I remember my greek correctly "Xena" translates as "female stranger"
tty

Actually, Xena is a totally fictional TV character. There never was a greek female warrior named Xena. It's all fantasy.

Noting the lack of female named planets, I have suggested "Artemis" as a good name. Artemis was the goddess of hunting, nature and women in ancient Greece.
(Diana is the latin name, but that is already taken on earth )

[Guest_BruceMoomaw_*]

I hope they name it Persephone. That was the name that James Christy originally intended to hang on Pluto's moon -- and it would have been magnificently appropriate poetically, given that it and Pluto perpetually keep their faces toward each other -- but by sheer dumb bad luck his wife was named Charlene and he felt the obligation to honor her, thereby both fouling up a beautiful metaphor and creating a moon which will forever be confused with Chiron. As for as I'm concerned, Christy's wife's real name is Mud. But in any case, Ceres' daughter is well overdue for an honoring.

[paxdan]

damn there goes my favorite mnemonic:

my very efficient memory just stored up nine planets

[David]

I hope they name it Persephone. 

There is an asteroid 399 Persephone; and also a 26 Proserpina (the Latin equivalent). This really ought not be any bar to the adoption of either of those names, as many of the asteroid names double the names of other bodies in the Solar System, like 593 Titania, 113 Amalthea, 577 Rhea, 106 Dione et cetera.
Although in looking for names of Roman gods to use for planets, "Minerva" and "Vulcan" seem to have been missed. And I dare say no one will want to name a planet "Bacchus"...

[Guest_BruceMoomaw_*]

Tombaugh's group was actually leaning toward naming Pluto "Minerva" until that 11-year-old British schoolgirl came up with her famous suggestion. (Better than Percival Lowell's wife, who -- after suing for years to try and acquire all his observatory's funds for herself -- suggested that they name the planet after herself.)

[elakdawalla]

One thing I've discovered about elementary age kids, after doing astronomy nights and LEGO robotics with them, is that they are a lot smarter and more sophisticated than many adults give them credit for.  And they really seem to appreciate an adult giving them an honest "we don't know for sure" answer.

So I'd give them JRehling's curriculum through Neptune and then "take the bull by the horns" with them on Pluto and KBOs.  I'd explain the reasoning behind both sides of the planet/not planet debate, then ask them what they thought.  It would be a great exercise in observation, logic, reasoning, testing hypotheses, and debate.  From what I know of fifth graders, they can certainly handle the ambiguity and would delight in knowing that their opinion is as good as anyone else's.

I heartily agree. In my experience, fifth graders find it wonderful to discover that there are questions that no one knows the answer to.

One thing I find terribly sad about the intersection of public education and the "what is a planet" debate is that no definition of "planet" is likely to include fascinating worlds like Io, Enceladus, or Miranda. Kids are taught about Pluto -- a place we've never been to -- but not about Titan, a world that's bigger and much more dynamic than either Pluto or Mercury. In my book, "planets" are things that wander across the sky; "worlds" are places that we can (or have, or will) go to visit.

Sometimes tiny rocks like Tempel 1 and Eros get promoted to "world" status, and that's all right as far as I'm concerned. Explain to a fifth grader (or even a second grader) that if they jumped off the ground on one of those worlds, they'd fly off into space -- they think that's pretty cool. Especially if you jump up and down while you're explaining it to them. (You can invite them to jump up and down, too, but then you have to get them to stop!)

[RedSky]

Although in looking for names of Roman gods to use for planets, "Minerva" and "Vulcan" seem to have been missed.  And I dare say no one will want to name a planet "Bacchus"...

I have an old astronomy textbook from 1869 (no, I'm not THAT old ... I rescued it from an estate sale junk bin). Your post reminded me of this page in the book. Looks like Vulcan had been tried once before as a planet's name. (besides Spock's homeworld).

[Guest_BruceMoomaw_*]

Yes, the Vulcan story is a classic of how Mother Nature keeps playing tricks on us. (I believe there was even a book published about it a few years ago.)

Short version: after it was discovered that Uranus wasn't quite where it should be in its orbit, the idea that there was another planet perturbing it was only one of the theories to explain this -- another was that Newton's gravitational law was very slightly off. The New Planet explanation -- namely, Neptune -- turned out to be the correct one. So when similar oddities were discovered in Mercury's orbit, the astronomical community naturally jumped to the conclusion that an undiscovered planet closer to the Sun than Mercury was, once again, the explanation -- and one unfortunate prominent French astronomer (can't remember who it was) actually swore that he'd seen the thing during a solar eclipse in (I believe) 1869. But that time, it turned out that the explanation really WAS subtle flaws in Newton's gravitational theory, as finally nailed by Einstein. There are times when it is hard to avoid the conclusion that God is pulling our leg.

[tty]

  Although in looking for names of Roman gods to use for planets, "Minerva" and "Vulcan" seem to have been missed.  And I dare say no one will want to name a planet "Bacchus"...

How about Terminus, the roman god of borders out there on "the borderland of Sol" to quote Larry Niven? Or perhaps Boreas the greek god of the north (or the north wind at least). Or Thule, a semi-mythological land of the far north. However I agree that Persephone would be a good choice.

tty

[dvandorn]

But if you call it Terminus, we'll have to establish the First Foundation there, and that's just asking for a whole lot of problems down the road...

Seriously, Terminus would indicate a border, and I'm pretty certain that this new KBO is not the most outlying of the large KBOs out there. Let's save the distinction of the name Terminus for something that truly does mark a natural boundary.

-the other Doug

[ilbasso]

The observation that Neptune was discovered because people were trying to explain the disturbances in Uranus' orbit also brings to mind a debate we should have on what it means to "discover" a planet. We have 100+ extrasolar planets that have been "discovered" but never observed directly. Most of these "discoveries" are based solely on the inferred presence, size, and motion of an object based entirely on its effects on its parent star. So to be consistent, shouldn't we say that the person who discovered Neptune was the person who first hypothesized its existence based on the perturbations of Uranus' orbit? The actual visual sighting of Neptune was only the "confirmation" of its existence, using today's logic.