Do you think Pluto is a Captured asteroid or a planet?

[Hunter Parasite]

What do you think? I think its a planet. yay.

[julesstoop]

Neither.

I don't believe PLuto was captured (from another star) by our sun: I think it originated from parts of our own solar nebula.

But... since PLuto seems to be - in many ways - more like one of the moons of Uranus or Neptune, or even like a gargantuan comet, and seems to have quite a few 'equal' brothers/sisters I don't consider it a full fledged planet either.

I think the KBO's - of which I'd say PLuto and Charon are two - are in many ways somewhat comparable to the planetoids (asteroids) between the Mars and Jupiter orbits.

[hank]

Do you think Pluto is a Captured asteroid or a planet?

What do you mean by "captured asteroid"?

- Hank

[Scorpiove]

I think the KBO's - of which I'd say PLuto and Charon are two - are in many ways somewhat comparable to the planetoids (asteroids) between the Mars and Jupiter orbits.

Pluto is really to big to be considered a simple asteroid. After all its bigger than what scientists consider to be the biggest asteroid "Ceres". Also the composition of Pluto and Charon are really different from asteroids in the main belt. I think Pluto would be more comparable to Triton.

[Malenfant]

Pluto is a KBO - a big planetoid made of ice, it's not a captured or escaped anything. Though historically it's classed as a planet and should stay that way IMO.

[julesstoop]

I think the KBO's - of which I'd say PLuto and Charon are two - are in many ways somewhat comparable to the planetoids (asteroids) between the Mars and Jupiter orbits.

Pluto is really to big to be considered a simple asteroid. After all its bigger than what scientists consider to be the biggest asteroid "Ceres". Also the composition of Pluto and Charon are really different from asteroids in the main belt. I think Pluto would be more comparable to Triton.

And Triton could just be a large KBO captured by Neptune...

There are no clear divisions here, but it's evident that more or less past the orbit of Neptune a lot of smaller (than Neptune) objects can be found in comparable orbits. Just like the orbits of the inner asteroids, these orbits are in general considerably more excentric than those of the 'real' planets.
PLuto happens to be one of the largest (and closest to the Sun) of those objects.

I agree we can't 'just' decide PLuto is not a planet any longer: it simply has had that status for too long.

[PlutonianEmpire]

Pluto is a KBO AND a planet. It is a KBO planet.

[Dollan]

Here we go again... planet, or asteroid. KBO, or planet, or planet AND KBO asteroid, or KBO potato badger coffee lily field whatsit mithingie jangle-rummy!! Argh!!!

Let's just call them "worlds" and be done with it! Why people insist on putting so much effort into deciding how to *label* a body, and so little into the body itself.....

Whoof. Anyway, the evidence seems to suggest that Pluto is a large KBO, long ago captured into a resonance orbit with Neptune. And in fact, most planetary scientists suspect that Triton itself is a captured KBO. Once New Horizons gets out there and investigates these things, we should have more definite answers.

Anyway, my above iratness is really just me trying to be funny. But, for my part, I could care less what Pluto is classified as. I have no interest in astronomical tradition in this case. I only want to know what makes Pluto tick!

And, for my part, I believe Pluto is indeed a large KBO, but certainly not the largest one out there. It is just the largest, closest one.

...John...

[Spaceman Spiff]

Sorry, HP, I can't vote because the option I'd choose isn't there: "planetesimal." I've discovered from my own poll that you can't edit choices afterwards, so 'oops!'.

Once, Pluto was proposed as an escaped moon of Neptune, but Pluto's moon, Charon, makes that a difficult scenario to model. Now some say Triton, Neptune's large moon, is a captured KBO, once loose like Pluto.

I think Pluto isn't a planet, but is on the way to becoming a planet. It just need a few tens of billion more years to merge with all the other KBOs to form a nice little ice planet about the size of Mars or maybe Earth at 50 A.U. or so. Since the sun goes to Red Giant to White Dwarf well before then, many fail to consider this as an end point. The death of the Sun won't stop this, since it just loses some mass as a strong solar wind. That wind might cause the KBOs to drag and move in, speeding up their merging into a final planet.

Even if Pluto isn't a planet, it should still be a very interesting world to see. Pictures of the surface could put Mercury to shame, for example. Even Ceres is proving quite intriguing after all.

Spiff.

[Spaceman Spiff]

Oh yes, I forgot to add:

I agree we can't 'just' decide PLuto is not a planet any longer: it simply has had that status for too long.

Let's just call them "worlds" and be done with it! Why people insist on putting so much effort into deciding how to *label* a body, and so little into the body itself.....

it makes me wonder if the situation of Pluto as a misidentified planet for so long was inevitable from the statistics of planet formation.

One day, planetary scientists will be able to run computer simulations of planet formation so powerful and accurate that they'll correctly model all the outer planetesimals hanging around for billions of years, and that some of them get dragged inwards and captured into resonance by some gas giant. Then, they'll also be able to model which planets could support life and give rise to intelligent alien civilisations that invent telescopes and spacecraft. Then they'll be able to model how many civilisations emerge with some odd outer planetesimal in just the right place and of the right size to look like a planet, and then decades later turn out not to be and cause years of arguments about status. Maybe these planetary scientists will find 99% of civilisations have this problem.



Spiff.

[Malenfant]

it makes me wonder if the situation of Pluto as a misidentified planet for so long was inevitable from the statistics of planet formation.

It isn't.

Pluto was classed as a planet simply because nothing else was discovered in its neighbourhood for 70-odd years.

Ceres was probably classed as a planet when it was first discovered in 1801, but then other bodies were discovered in rapid succession in the same region, and it became obvious that there was actually a swarm or belt of bodies between Mars and Jupiter. Hence, those were called asteroids and not planets.

The problem of Pluto's classification is that it's had 70 years to settle into and become accepted in the public consciousness as a planet. That cannot be undone easily at all, no matter how much pedantic scientists want that to happen.

Factually speaking, Pluto is a KBO. Whether or not it is a planet depends on your definition. Personally, I think a very good definition of a planet is as follows:

"A planet is a body over 1000 km in diameter that orbits a star, that is not part of a swarm or belt of similarly sized objects that orbit within 10% of its orbital distance from its primary"

Optionally, one could add "that has never been massive enough to fuse any elements in its interior" if you want to leave out brown dwarfs from that definition. Either way, the fact that it has an atmosphere (sometimes) and a moon doesn't make it a planet.

Pluto would be an exception to this definition purely for historical/cultural reasons.

[Hunter Parasite]

Do you think Pluto is a Captured asteroid or a planet?

What do you mean by "captured asteroid"?

- Hank

It means that Pluto was not formed when the solor system was. Meaning it is asteroid captured by the Suns gravity.

[Malenfant]

Sorry but again I'm not getting the point of what you're asking.

You seem to think that our opinions matter regarding something that is already known. We know that Pluto is a KBO. There is a miniscule chance that we just happen to have discovered a body as the ninth planet that actually originates from outside the solar system, but in all likelihood it formed along with the sun and other planets.

The only purpose of this poll seems to be to determine whether people know this already, and I'd wager most people here do.

[hank]

Do you think Pluto is a Captured asteroid or a planet?

What do you mean by "captured asteroid"?

- Hank

It means that Pluto was not formed when the solor system was. Meaning it is asteroid captured by the Suns gravity.

Why would you (or anyone) think that Pluto was not formed when the solar system was?

- Hank

[Dollan]

Well, it's certainly not out of the realm of possiblity that some KBO's are captured bodies from other systems (althogh personally I doubt it). In fact, wasn't there some speculation a while back that Sedna could be such a body? Don't know if that line of thought made it very far, though.

...John...

[hank]

Well, it's certainly not out of the realm of possiblity that some KBO's are captured bodies from other systems (althogh personally I doubt it). In fact, wasn't there some speculation a while back that Sedna could be such a body? Don't know if that line of thought made it very far, though.

...John...

I believe the possibility that Sedna was captured from a passing brown dwarf was based on an analysis of its unusual orbit, and would not be applicable to Pluto. AFAIK there is no evidence to suggest that Pluto is a captured body.

- Hank

[Dollan]

Oh, I would bet that such a captured body could eventually find its way towards Pluto's orbit, perhaps by a gravitational encounter or few with some of the larger massed objects theorized to be out in the Kuiper region.

But please note: I'm not saying that Pluto IS such an object. Simply that there is always the possibility of such an object entering into a Pluto-like orbit.

...John...

[tony873004]

Here's a link to a page I wrote about the possibility of Sedna being captured into Solar orbit.

http://www.orbitsimulator.com/gravity/a ... sedna.html

It is theorized that captures would have occured early in the Sun's life when it was still part of a star cluster. The encounter speed between the Sun and whatever object the captured objects originally orbited must be very slow. In the simulation described, the encounter speed is 1 km/s at infinity, with a passage distance of 200 AU. 1 km/s is a likely encounter speed between objects in a star cluster.

After departing the star cluster that it formed in, it is unlikely that the Sun has ever passed within 200 AU of another star or brown dwarf. And if such an encounter did happen to take place, it is likely that the encounter speed was in the 10's of kilometers / second, much too fast for captures to take place.

Although most of the orbits of the captured objects in the simulation are elliptical and Sedna-like, there are a few that are near-circular. But they orbit much farther than Neptune. The simulation only follows 20 test objects originally orbiting the brown dwarf. Likely, there were thousands of possible candidates, so maybe closer circular orbits would have occured. And maybe the Sun had several encounters before leaving its birth cluster.

Any captured object whose orbit intersects Neptune's orbit would likely have been ejected from the solar system by Neptune's gravity, or thrown into a higher orbit whose perihelion still intersects Neptune's orbit. Such objects are known as scattered-disk objects.

A few Neptune-crossing survivors could find refuge in Neptune's resonance points. Pluto and other more recently-discovered "Plutinos" have a 3:2 resonance with Neptune that prevents them from ever making close passages to Neptune. When they get too close, Neptune seemingly repels them. Here's an animated GIF of such a resonance. The blue dot is Neptune. The purple path is the orbit of Pluto in a rotating frame whose period matches Neptune's orbital period.



I think it would be difficult to wander into a resonance point, as some mechanism must exist to slow the object and allow it to be captured in the resonance point. I imagine Pluto could have been captured directly into a 3:2 resonance point, but it's probably more likely that it formed there from a population of smaller objects trapped in the same resonance point.