Astronomers say Pluto is not a planet (Eight Planets)

Yahoo ^

[foreverfree]

Paradox, what are those gross looking things on Pluto's tongue?

ff

[dr_lew]

It's interesting to read my old Abell astronomy text, Exploration of the Universe ( 1964 ). It cites the discrepancy between the large estimated mass ( 0.9 Earth-mass ) and its "small" estimated diameter ( by Kuiper! ) of 3600 miles ( Now determined to be 1400 miles.)

Abell takes the mass very seriously as this was the whole basis for its discovery, even though he notes that it was determined to be too small to cause the perturbative effects that Lowell thought he had determined. He notes that Lowell "has justly earned the honor for its discovery," but this did not hold up, of course.

Pluto's stature has clearly been diminished with time, so its demotion can be seen as acknowledgment of a mistake. OTOH, it was discovered optically, and even if it represents a class of outer objects, it was the only one known for many years, and I don't see anything wrong with a "freeze" in the nomenclature extant for the last seventy years.

Planethood is, after all, a rhetorical and even a poetical designation. Pluto stands as the outpost of the solar system, and its name is perfect.

I wonder if this change will not suffer the fate of "New Coke". Perhaps popular usage will ignore the authority of this commision, or whatever it is, and adhere to the "Classic Planets".

[KevinDavis]

[mwyounce]

"It was unclear how Pluto's demotion might affect the mission of NASA's New Horizons spacecraft, which earlier this year began a 9 1/2-year journey to the oddball object to unearth more of its secrets."

It's not going to unEARTH anything! It will have to "... unpluto more of its secrets"! :-)

[garbageseeker]

Pluto will always be the ninth planet.

[SunkenCiv]

Michael Brown had a page on his university website saying (a few years ago) that the then-recent discovery of a large (but not as large as Pluto) body should not be considered the discovery of a planet. But when UB313 was announced (and after all the controversy over who actually discovered it died down), he changed his mind. He seemed to change it again when the seven-member panel unveiled its recommendations. Soooo, I guess being a turncoat has cost him a planet, and FWIW, a fan (me).

[SunkenCiv]

Wholeheartedly agree.

[Central Scrutiniser]

Pluto isn't a planet, its a KBO, and it joins thousands of others.

If Pluto is a planet, then so is Ceres and Xena and perhaps Sedna and Quaror.

[SunkenCiv]

LOL! This group of astronomers can go be fruitful and multiply, but not in those words. [adapted from Woody Allen]

[Central Scrutiniser]

No, Neptune is on the eplictic plane that all the other planets are on, Pluto overlaps Netpunes orbit, not the other way around.

All the planets orbit in essentially the same allignment relative to the sun, pluto's orbit is several degrees off of that which all the other planet's orbit.

[IslandJeff]

Layman here checking in. Intuitively, I agree with the decision, though "planetary status" will become less and less important the better technology does in identifying KBOs and even big stuff in the Oort Cloud.

Pluto will remain in its eccentric orbit, and as a nice relic of history and, perhaps, a catalyst in the art of astronomy. This sounds more and more like a scientific GroupThink dynamic. In the big scheme of things, there's still a google of research to be done out there, and every solar system discovery, no matter how seemingly mundane, still is exciting in the context of how hard scientists are working on these things.

I'd only heard recently of Ceres - that asteroid thingy that's spherical and has a regular orbit. Anyone have an orbit graphic for it? Absolute Magnitude?

-Jeff

[SunkenCiv]

Well put!

[SunkenCiv]

"The Ecliptic is the plane of the Earth's orbit. Most of the planetary orbits are close to this plane. Pluto's orbit is inclined at an angle of 17.14 degrees to the ecliptic plane - the largest deviation of any planet." -- http://pluto.jhuapl.edu/science/glossary.html

http://bobscrafts.com/bobstuff/planets.htm

Mercury -- "Its orbit is inclined to the plane of the ecliptic by 7 degrees (The plane of the ecliptic is the plane of the Earth's orbit. All planets orbit in planes that are nearly the same as that of the Earth.)."

Venus -- "Its orbit is inclined at an angle of 3.4 degrees."

Mars -- "The orbit's eccentricity is 0.093 at an inclination of 1.9 degrees."

Jupiter -- "The orbit has an eccentricity of 0.048 at an inclination of 1.3 degrees."

Saturn -- "Its orbit has an eccentricity of 0.056 with an inclination of 2.5 degrees."

Uranus -- "The orbit has an eccentricity of 0.047 and an inclination of 0.8 degrees."

Neptune -- "It has an eccentricity of 0.009 and an inclination of 1.8 degrees."

[IslandJeff]

Please forgive my ignorance, but would the relative lack of eccentricity WRT Neptune and Terra Firma on the Ecliptic indicate something like Neptune being a dying star of sorts, perhaps central to the formation of Earth - sort of like us all exploding outward from somewhere else and settling around nice ol' Sol? What also confuses is the retrograde rotation of Uranus (or is it Neptune?).

Great thread, thank you so much for keeping this beancounter on your ping list.

[Number57]

OK - Back in the day, planets orbited stars/suns... moons orbited planets...

Now, moons orbit stars/suns while being orbited by moons and being continually billed by Orbitz.



Man. This was much easier in grade school.

[IslandJeff]

We were just born too damned soon.

[SunkenCiv]

Neptune is smaller in diameter than Uranus, but a bit more massive; neither Neptune nor the other planets should be considered stars (dying or otherwise); Uranus is the planet with the axis tipped nearly into the ecliptic, IOW, one or the other of its polar regions faces the Sun during part of its orbit. Which is pretty wild.

Uranus should be excluded, its origin is obviously different from the other planets, and its axis is too freaky. :')

Now that Pluto is removed, Mercury is the smallest, and is too small, and its orbit is in precession, making it too weird to be considered one of the planets. :')

With the removal of Mercury, Venus is the only one left without a moon, which makes it too strange to remain. Out it goes. :')

Mars is also too small, and is less dense than the Earth. Also, it doesn't have proper moons (just oddly shaped space debris). Out it goes. :')

There are therefore only four planets -- Earth, Jupiter, Saturn, and Neptune.

[IslandJeff]

Point very well-taken. I almost thought you were being facetious... ;-) FOUR! NO MORE!

So is the plane of an axial rotation due to solar magnetism or is magnetism the result of the axis? My guess would be the latter, because ions going 30-odd AU into the frozen void shouldn't have caused dramatic rotational tilting unless, as is possible in my pet barstool paradigmatic cosmology tonight, that Sol is merely where the Solar System settled, rather than being proximal to its origin.

Off to bed. Give it some thought (and put me on your GGG list, if you don't mind).

J-

[SunkenCiv]

I think we should work on this four planets idea. Its time has come!!! ;')

So is the plane of an axial rotation due to solar magnetism or is magnetism the result of the axis? My guess would be the latter, because ions going 30-odd AU into the frozen void shouldn't have caused dramatic rotational tilting unless, as is possible in my pet barstool paradigmatic cosmology tonight, that Sol is merely where the Solar System settled, rather than being proximal to its origin.

Uranus is a puzzle from a uniformitarian perspective, although a number of ideas have been put forward. Since the Uranian moon system appears to be pretty conventional (unlike that of Neptune) it seems likely that the tipped axis of the planet was caused by something after the moons entered orbit (regardless of their origin). If it was caused by an impact, then it must have been one doozy of an impact.

It's also possible that the axis was tipped by some impact or other encounter (perhaps the thick gaseous atmosphere which covers a presumed rocky core arrived from a direction perpendicular to the ecliptic) before the moons were there. Gosh, I guess I'm no help at all.

My guess is, the magnetic field of the planet doesn't pertain to the axis of rotation. Let's see...

Uranus: Magnetic Field And Magnetosphere
by C. T. Russell and J. G. Luhmann
Quicktime movie (other source)

If the intrinsic magnetic field of Uranus had been nearly aligned with the rotational axis, as the planets previously visited were, the polar axis of the magnetosphere, or the polar cusp as it is called, would have been aligned with the solar wind flow as Voyager flew by the planet. Ironically, the magnetic axis of the intrinsic magnetic field of Uranus was far from spin axis-aligned, so that the solar wind blew nearly perpendicular to the magnetic axis, as it does at Mercury, Earth, Jupiter and Saturn. Thus, while Uranus has an unusual intrinsic magnetic field, the resulting magnetosphere was found to be very Earth-like.

[IslandJeff]

It's also possible that the axis was tipped by some impact or other encounter (perhaps the thick gaseous atmosphere which covers a presumed rocky core arrived from a direction perpendicular to the ecliptic) before the moons were there. Gosh, I guess I'm no help at all.

You are selling yourself short, while opening up a new can of worms. If Uranus, indeed, has a terrestrial core, the limits of theoretical science at least suggest a core composed of heavier, possibly-metallic (and well beyond carbon 16) elements. Now given the mass of the gas giant (even if it's mostly methane or whatever), that gaseous mass, given Newtonian mechanics, is creating God-knows-how-much-pressure on what could likely be a nickel-iron-lead(?) alloy virtually impossible to create at "STP".

Let's keep up the Four and No More. I like this "outside the box" stuff. Uranus, though you obviously weren't a fan of "2010", could still be a major teacher confined to scientific house arrest.