[X] My Assistant

[Guest_Myran_*]

NASA sponsored astronomer Michael Brown of CIT just announced he have found a 10'th planet.
The claim was made for one object based on its brightness alone and that for one object at 3 times the distance of Pluto. In short its smack in the middle of the belt of other KBO's.
The guy claim he was forced to reveal his data since a hacker had threatened to release information about the object.
Im strongly unconvinced about that story.
Why then claim it to be a planet rightoff. More likely think this guy must be looking for the fame of Clyde Tombaugh.
Without any infrared measurements or to establish the albedo properly which would have given a guesstimate of the objects size he singlehandedly claim a KBO planet, this should get the Bad astronomy 1'st price prize for preposterous extrapolation from a single unconvincing piece of scientific data.

[CosmicRocker]

Myran:

I really don't have a lot of background information on this discovery, but I suspect you are correct about the decision to "go for the glory." But who wouldn't try for that if they had some strong data and the data somehow escaped to the Internet? Especially, consider the fact that there is no clear definition of the word "planet." It is certainly time for the scientific community to define that imprecise word.

I think there is some IR data from the Spitzer Space Telescope.

I think his thought that his data was hacked was a misunderstanding, if this explanation is accurate. http://groups.yahoo.com/group/mpml/message/15283

Perhaps the most significant outcome of this event will be the IAU finally coming to grips with the definition of a planet. This article claims we will have a definition this week!

http://www.nature.com/news/2005/050801/full/050801-2.html

I think I know how I would define a planet. It will be interesting to see how the IAU does. I now see that there is a lot of discussion on these topics elsewhere in this forum, but I'll have to explore them tomorow...

[volcanopele]

NASA sponsored astronomer Michael Brown of CIT just announced he have found a 10'th planet.
The claim was made for one object based on its brightness alone and that for one object at 3 times the distance of Pluto. In short its smack in the middle of the belt of other KBO's.
The guy claim he was forced to reveal his data since a hacker had threatened to release information about the object.
Im strongly unconvinced about that story.
Why then claim it to be a planet rightoff. More likely think this guy must be looking for the fame of Clyde Tombaugh.
Without any infrared measurements or to establish the albedo properly which would have given a guesstimate of the objects size he singlehandedly claim a KBO planet, this should get the Bad astronomy 1'st price prize for preposterous extrapolation from a single unconvincing piece of scientific data. 

Even near 100%, this object would still be about the size of Pluto.

[Guest_Myran_*]

CosmicRocker: When I posted this, we didnt have much information either.
But thank you for the info and links.
It turned out that this discovery got a lot of attention in another thread whereas my post here got left in the cold until now. But it will be interesting to learn what
IAU thinks.

volcanopele: If its somewhat larger or smaller than Pluto doesnt matter.
If we could timetravel and tell Clyde Tombaugh and the astronomical community back then the true size of the object they had found -Pluto-, im certain they would he have to think not only once or twice before using the term 'planet' for one object of the diminutive size it turned out to have. Size alone, and now we know so much more and have put Pluto into a context, if the discovery of Pluto had taken until recent years, im personally certain we wouldnt have this discussion at all!

Viewing the other discussion of this same subject here, it obvious than many have gotten so used to the notion that Pluto is a planet that we might have to live with that idea.
But one mistake made 70 years ago, does in no way neccesitate that we make the same mistake again!
-"-

(Some background that might or might not be correct written off the top of my head from what I remember reading in many old astronomical textbooks:
Pluto was named a planet at its dicovery for several reasons, one of them that it was thought to be much larger and massive than what it eventually turned out to be.
Pluto was thought to be so massive that it affected the orbits of Uranus and Neptune, when astronomers couldnt match the values they had gotten for Plutos albedo, magnitude and the resulting size there were some wild suggestions that Pluto would about 5000 km and be incredibly dense. Another suggestion was that we did only see Pluto as a starlike object since we did only see the reflection of the sun in one ocean of liquid gas of a larger world.

Plutos status as a planet have been questioned before, then in connection with speculations that it might be one escaped moon of Neptune - turned out to be wrong, Neptune have brought Pluto into a resonance but they might not have had any common past at all, with the exception of Triton that could turn out to be Plutos twin.)

[David]

volcanopele: If its somewhat larger or smaller than Pluto doesnt matter.
If we could timetravel and tell Clyde Tombaugh and the astronomical community back then the true size of the object they had found -Pluto-, im certain they would he have to think not only once or twice before using the term 'planet' for one object of the diminutive size it turned out to have. Size alone, and now we know so much more and have put Pluto into a context, if the discovery of Pluto had taken until recent years, im personally certain we wouldnt have this discussion at all!

I'm not sure size should be the only, or even principal, criterion for determining "planetary" status; that is, if we are going to retain the term "planet" at all.

Remember that "planet" was originally used as a word for any celestial body that had visible, regular motion against the background of "fixed" stars: not just Mercury, Venus, Mars, Jupiter, and Saturn, but also the Sun and Moon. Comets, whose periods were so long that they could not be identified as the same objects when they returned, were viewed as transient (perhaps atmospheric) phenomena, not similar to planets; other objects were invisible from Earth without apparatus that did not yet exist.

Following the Copernican revolution, the Sun ceased to be "a planet", as (in terms of the entire system), it did not "move". As motion, as seen from earth was no longer a criterion, then the Earth itself could be "a planet".

The telescopic discoveries of Galileo, Huygens and Cassini showed that there were many objects moving around Jupiter and Saturn just as the Moon moved around the Earth; as their motions, viewed from Earth, were not independent of their primaries, they were given a secondary status and not classed as "planets", though by earlier criteria they might well have been. By analogy with these satellites, the Moon also
was demoted, and "a planet" was now defined as "an object moving around the Sun".

One problem with this general definition came with the realization that comets were also satellites of the Sun -- but they were eccentric enough in other ways to merit their own classification. A more serious problem arose with the discovery of the asteroids. Indeed, the questions regarding Pluto and 2003 UB313 were foreshadowed in Piazzi's discovery of Ceres in 1801. Initially Ceres was celebrated as a new planet, just like Herschel's discovery of Uranus in 1781. By the criteria then used -- an object revolving around the Sun with a not-too-elongated orbit -- Ceres was a planet. The trouble came as astronomers over the next few years began to find more and more "planets" in the Main Belt. By the 1850s, the list was becoming unmanageable and it was clear that the asteroids were much smaller than the other planets -- by now eight (with the addition of Neptune in 1846). The asteroids were therefore packed off into their own section of the almanacs. Only at this point does size become an issue in terms of planetary definition. At this point (and up to the present day) the criteria include at least the following:

1) A planet is a natural satellite of the Sun
2) A planet has a not-too-elongated orbit (i.e., it is not a comet)
3) A planet is at least bigger than Ceres (a criterion to some extent redundant with 2), as no comet is bigger than Ceres)

Using these criteria, Pluto was correctly labelled "a planet" in 1930; the only cause for concern being the fact that its orbit is both elongated (somewhat) and tilted (a lot), and I recall that before we ever started talking about KBOs there were proposals to reclassify Pluto as "a comet" -- which was, indeed, the only alternative at the time, as it was obviously neither a Main Belt asteroid nor a moon. On the other hand, Pluto was believed to be, and is, far larger than any comet, which would make its presence in a list of comets far more anomalous than in a list of planets. After all, in the context of all the thousands of objects in the Solar System, Pluto is not that small; besides the other eight planets, only seven moons are larger (the four Galilean satellites, Titan, Triton, and our Moon).

Now of course we have a new list of additional objects (e.g. Sedna, Orcus, Quaoar, Varuna) that fit criteria 1) and 2). Whether they fit 3) is the present dilemma. They are (probably) larger than Ceres; but criterion 3) only says "at least bigger", but does not tell us how much larger than Ceres "a planet" has to be. As these objects are currently not being labelled "planets", one supposes that the real answer is "at least as large as Pluto". And indeed, if we want to avoid the planetary crunch occasioned by the accumulation of asteroids in the first half of the 19th century, that will have to be the answer.

Now we have 2003 UB313. And if our criteria for "a planet" are now: 1) A natural satellite of the Sun whose orbit is not 2) too elongated and is 3) at least as big as Pluto, then 2003 UB313 is a planet. And that is a conclusion that is not, in itself, unacceptable; there is no special reason to limit the number of planets to nine or fewer, and we would be in an even worse terminological muddle if, in 1781, tradition-minded astronomers had sought ways to avoid calling Uranus "a planet".

The problem, of course, will arise if a lot of objects bigger than Pluto are discovered out in the Kuiper Belt or beyond. Once we get beyond half-a-dozen (and so up to fifteen planets) the situation, if it gets to that (and there's no saying it will) will probably be felt to be intolerable. At that point, I would expect Pluto and his transneptunian siblings to be demoted to some new status, somewhere between "planet" and "asteroid". However, that situation has not yet been reached, and may never be reached; and there is plenty of time to think about possible consequences. At present, however, it seems to me that the safest thing to do is to accept 2003 UB313 as a planet, with the proviso that the term can be revoked if it becomes inconvenient.

However, if Pluto is pre-emptively demoted, simply in order to exclude 2003 UB313, I have to wonder what will be done if a distant transneptunian object is discovered that is larger than Mercury? Will Mercury also lose its status as "a planet"? Or will we add a fourth criterion to the three above, "A planet must not orbit beyond the orbit of Neptune"?

[CosmicRocker]

David: That was an insightful description of some of the historical perspectives the IAU must be considering, and I learned a lot reading it. Thanks. I would have to guess that they must also be considering recent discoveries and our better understanding of the origin and evolution of the solar system.

To your list of parameters, I would also suggest adding orbital inclination and some other measure of orbital stability. If an object's future is uncertain, I don't think it should be classified as a planet.

What I find most amazing is that we have the opportunity to be at least peripherally involved in the discussion of the definition of a word that is thousands of years old. It has been reported that the IAU has been working on this definition for the past year and that they expect to finalize a definition this week.

That should be quite interesting.

[Guest_Myran_*]

Um hold a second here David , I didnt question the status of Pluto in my reply, only had a lookback on some of the reasons that world ended up with the label.
And again, since people (including many astronomers) have gotten used to view Pluto as a planet quoting myself 'I think we have to live with the idea'.
So I didnt talk about demotion of Pluto, Mercury or any other world that have been declared a planet.

But as said, we have found many more pieces of the puzzle that makes up the solar system. And one far from unimportant one is this Kupier belt.
UB313 is just one more addition to a list that have become rather long already.

And yes, I do look ahead, since im personally convinced theres not only a dozen larger objects still to be found, but far more perhaps several hundreds.

You used the terms "planet" and "asteroid" and there have been a suggestion some years back thats based on both; 'planetoid' where the name would hint that its the building block that planets are made from.

So yes, I have no problem using the term planetoid for UB313 keeping both sides of the fence happy.

[Jeff7]

I figure this is going to turn out like Saturn. How many moons do they say it has? It keeps increasing. And what exactly is a moon? Chunks only a few miles wide are being found and called moons. "Big boulder" or "debris" seem more appropriate terms.

In the coming decades, as we send more probes out into the Kupier Belt, and as better telescopes are built, we'll no doubt find a great many objects orbiting out far, as Myran also believes.



Hm, new idea for declaring something a planet - an orbiting body must be a specific percentage of either the mass or diameter (or a combination of both) of the body that it orbits.
Example - Mars has two moons, and they're both fairly small. But it seems ok because they are the only ones there, and because it's a small planet. Now put those moons around Saturn. There are lots of things there that are that size, and they are puny compared to the big gas ball they orbit. Are they still moons?

[Guest_Myran_*]

Jeff7 said: I figure this is going to turn out like Saturn. How many moons do they say it has? It keeps increasing. And what exactly is a moon? Chunks only a few miles wide are being found and called moons. "Big boulder" or "debris" seem more appropriate terms.

Very good example, and there you happened upon the core of my thinking.
One of those boulders that are inside the ring system should be considered to be part of the same rings.
But those outside the rings might be considered a moon, unless if very minor in size.
So lets apply this line of thinking to the Kupier belt: Pluto are at the inner edge of same belt and could be viewed as being outside it, so Pluto can keep its planetary status. Yet UB313 are firmly placed among many other Kupier belt objects with orbits both inside and further out from the sun and so it belong to the group and can in no way be seen as a member of the planetary family.

[David]

I figure this is going to turn out like Saturn. How many moons do they say it has?

Forty-seven at last count. But there's a way to go before it matches Jupiter's sixty-three.

And what exactly is a moon? Chunks only a few miles wide are being found and called moons. "Big boulder" or "debris" seem more appropriate terms.

I've often thought that a distinction should be made between "moons" (objects similar in size and shape to our Moon) and other natural planetary satellites, which - on the model of the coinage "planetoids" - might be called "selenoids". If the former category were restricted to objects at least as big as Mimas, no one planet would have more than seven "moons".

Hm, new idea for declaring something a planet - an orbiting body must be a specific percentage of either the mass or diameter (or a combination of both) of the body that it orbits. Example - Mars has two moons, and they're both fairly small. But it seems ok because they are the only ones there, and because it's a small planet. Now put those moons around Saturn. There are lots of things there that are that size, and they are puny compared to the big gas ball they orbit. Are they still moons?

Well - let's try that scheme. Ranking objects in order of relative size in relation to their primary, we have:

.49 Charon
.27 Moon
.1 Jupiter
.087 Saturn
.055 Triton
.043 Titan
.037 Uranus
.036 Ganymede
.035 Neptune
.034 Callisto
.031 Titania
.030 Oberon
.025 Io
.023 Umbriel
.023 Ariel
.022 Europa
.013 Rhea
.012 Iapetus
.0093 Dione
.0092 Miranda
.0092 Earth
.0088 Tethys
.0087 Venus
.0084 Proteus
.0069 Nereid
.0065 Phobos
.0049 Mars
.0041 Enceladus
.0039 Larissa
.0037 Deimos
.0035 Mercury
.0033 Mimas
.0032 Galatea
.0032 Puck
.0030 Despina
.0029 Sycorax
.0026 Portia
.0022 Hyperion
.0018 Juliet
.0017 Pluto
.0012 Amalthea
.0010 Phoebe
.0007 Ceres

I think the list is complete for relative sizes larger than Pluto/Sun, but I have only listed a few that are smaller for use as signposts. I guess Jeff7's definition works as well as others, but it provides no obvious answer to the question: "Where do you draw the line?"

The major problem that I see with this approach is that it makes it harder to draw parallels between bodies in the Solar System that may be similar overall, but happen to be in orbit around a different primary; e.g., if a particular moon happens to be a captured asteroid or comet, it would fall in a very different place in this list than its closest relatives would, because its primary is so much smaller than the Sun.

[ilbasso]

Then you also get into the asteroids with moons, like Ida/Dactyl. And what about the asteroids that are essentially two bodies in contact with each other?

[ljk4-1]

Definition of 'Planet' Expected in September

http://www.space.com/scienceastronomy/0606...definition.html

Historians and educators have joined astronomers in an effort to break a
deadlock on contentious discussions over a definition for the word planet.

[Guest_BruceMoomaw_*]

Wonderful! Think of all the fun they can have next trying to officially define "moon", "asteroid" and "comet". The debates in Laputa won't be in it by comparison.

[Guest_Richard Trigaux_*]

Wonderful! Think of all the fun they can have next trying to officially define "moon", "asteroid" and "comet". The debates in Laputa won't be in it by comparison.

Not speaking on going "up" is size. Jupiter, a gaz giant, orbiting round the Sun, is a planet... But larger gaz giants can still do this. When a gaz giant is much larger than Jupiter, it can remain luminous like a star for many hundred millions of years. When it is large enough to burn its deuterium, it becomes a brown dwarf, and still larger a red dwarf. Star or planet? where to set the limit? If it has nuclear reactions, it is a star, but if it turns around a star, it is a planet. Most stellar companions would rank after Charon, and even after Jupiter, into David's classification above.

Throw this stone into the debate, and look what happens (while keeping at safe distance)...

[ljk4-1]

Note scientists' attempts to introduce two new terms to strange new
worlds: Pegasids and Planemos.


Inside Exoplanets: Motley Crew of Worlds Share Common Thread

http://www.space.com/scienceastronomy/0606...m_pegasids.html

Scientists have discovered a correlation between the amount of heavy elements in
giant Jupiter-like extrasolar planets known as "Pegasids" and their parent
stars.


* Strange New Worlds Could Make Miniature Solar Systems

http://www.space.com/scienceastronomy/060605_planemos.html

Planet-like objects floating alone through space harbor disks of material that
could make other planets or moons, something like miniature versions of our
solar system, astronomers said today.