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SFJCody
http://groups.yahoo.com/group/mpml/message/15111
mike
Planet X, or perhaps Rama I.
slinted
Interestingly enough, it had already been found by another group and was given the designation K40506A. It has an elongated shape, 3.9 hour rotational period and a satellite. Total mass of it and its satellite weighs in around 30% of Pluto.

http://www.aas.org/publications/baas/v37n3/dps2005/320.htm
http://www.aas.org/publications/baas/v37n3/dps2005/786.htm
Bob Shaw
Hmmm... ...a candidate for a post-Pluto encounter, perhaps? Depends where it is, of course...
TheChemist
BBC article : Distant object found orbiting Sun
volcanopele
While K40506A/2003 EL61 now appears to be smaller than Pluto based on Spitzer data, another newly announced TNO, 2003 UB313 is defintely larger than Pluto, perhaps as large as Mars.

http://www.gps.caltech.edu/~mbrown/planetlila/index.html
http://cfa-www.harvard.edu/mpec/K05/K05O41.html
Sunspot
WOW............when will there be an official announcement?
Jyril
That's not all!

There are third large KBO discovery announcement today (MPEC 2005-O42).

The object, 2005 FY9, may also be larger than 2003 EL61!
volcanopele
QUOTE (Sunspot @ Jul 29 2005, 03:15 PM)
WOW............when will there be an official announcement?
*

a few minutes ago:

NASA-Funded Scientists Discover Tenth Planet
http://www.nasa.gov/vision/universe/solars...net-072905.html
odave
The article quotes Brown as saying it will be "visible with a telescope", but you'd better have a big one. S&T gives it a magnitude of 18.9 - Pluto is 13.8, and I have trouble seeing it in my 12.5" dob.

Very cool news. I wonder if this will stir the pot of the whole "is Pluto really a planet" debate...
Decepticon
Is the object at it's closest approach to the sun?
Decepticon
http://www.space.com/scienceastronomy/050729_new_planet.html

Update 11:27pm
remcook
Methane on the surface as well...another frozen-out atmosphere?
Looks like a job for Spitzer, Hubble, etc
very cool cool.gif
BruceMoomaw
According to the NY Times, it's nowhere near perihelion. Its 560-year orbit is extremely eccentric -- it's currently 97 AU from the Sun, but has a perihelion of only 35.5 AU -- and tilted an astonishing 44 degrees to the ecliptic, which makes it more understandable that it wasn't discovered before. As for its size: the
Spitzer Telescope cannot yet detect its thermal IR, meaning that it must be
less than twice Pluto's diameter -- but it would be bigger than Pluto even
if its albedo was 100%. It apparently has methane frost like Pluto; if its
albedo equals Pluto's 0.60, it must be about 3000 km in diameter as compared
to Pluto's 2270 km.

Meanwhile, we also have a THIRD big KBO announced today: 2005 FY9, which has
been detected by the Spitzer Telescope and is modestly smaller than Pluto --
along with 2003 EL61, this morning's false alarm, which turns out to be
smaller still. (The latter has a moon, which has allowed its mass to be
calculated at 30% of Pluto's.) Neither of these is small potatoes either,
though, except by comparison with 2003 UB313 -- they seem to be about 70-80%
of Pluto's diameter.

So now we can switch to wrangling drearily over whether the Solar System has
10 planets or only 8 (or 9, if you decide to rate 2003 UB313 as a planet but
not Pluto.) Alan Stern continues to insist that if something's large enough
to be rendered spherical by its gravity, it's a planet -- but that includes
Ceres and probably Pallas and Vesta, and in any case it containes
ambiguities of its own (even if you don't count Bizarro World from DC
Comics, which you may recall was cubical). Personally, I still favor
setting a maximum diameter of 2000 km as the arbitrary planet/nonplanet
dividing line, which will allow Pluto to retain its longtime seat in the
Planet Club without allowing too many newcomers to crash the party.
Myran
Bruce. Just wait until they have found a thousand objects with a diameter between that of Pluto and Mars's (and perhaps a few Earth sized ones also) , I dont think the schoolchildren of the future will have to memorize the names of a solar system of more of a thousand planets!
dilo
In a previous thread, few months ago, I proposed an arbitrary mass lower limit of 0.001 Earth masses for a planet definition and this translates in a 1500-2000 Km minimum diameter, depending on density. Even though mass is a more objective parameter than diameter (especially for non perfectly spherical objects), I must admit that can be very difficult or even impossible to measure it for so distant objects, if they do not have small satellites like Pluto or 2003EL61...
So a lower limit of 2000Km seems the best thing also to me, but only for now! Probably they will discover other far object larger than this in the next few years; in fact, as reported in the Space.com article, "Alan Stern, of the Southwest Research Institute and leader of NASA's New Horizons mission to Pluto, predicted in the early 1990s that there would be 1,000 Plutos out there. He has also contended, based on computer modeling, that there should be Mars-sized worlds hidden in the far corners of our solar system and even possibly other worlds as large as Earth."
So it seems we need a different approach, otherwise we would fall in the same ridiculous situation of natural satellites count: most of the ever increasing objects around giant planets are in fact boulders, very few kilometers across and otherwise classified as captured asteroids or planetesimals. If we really want to call them "moons", why do not include in this cathegory also rings particles ?!?
tedstryk
QUOTE (Myran @ Jul 30 2005, 12:37 PM)
Bruce. Just wait until they have found a thousand objects with a diameter between that of Pluto and Mars's (and perhaps a few Earth sized ones also) , I dont think the schoolchildren of the future will have to memorize the names of a solar system of more of a thousand planets!
*


If we do indeed make such discoveries, it will sure make exploration difficult. It might be the time to develope a large space-based array of telescopes to map them.
Alan Stern
QUOTE (Myran @ Jul 30 2005, 12:37 PM)
Bruce. Just wait until they have found a thousand objects with a diameter between that of Pluto and Mars's (and perhaps a few Earth sized ones also) , I dont think the schoolchildren of the future will have to memorize the names of a solar system of more of a thousand planets!
*



That day will come, in this century. And so what of it? School children aren't expected
to know the names of all the stars, and no one claims we should arrange the definition
of stars (or galaxies, etc.) just to keep the number of them small.

-Alan
Sunspot
Any idea what the dates would have been for the last perhilion passage and the next - also the expected magnitude?
alan
about 1700, roughly magnitude 14.5
next about 2250
Rob Pinnegar
QUOTE (BruceMoomaw @ Jul 30 2005, 05:42 AM)
Personally, I still favor
setting a maximum diameter of 2000 km as the arbitrary planet/nonplanet
dividing line, which will allow Pluto to retain its longtime seat in the
Planet Club without allowing too many newcomers to crash the party.
*


Yeah. A radius of 1000 km is a good dividing line. If we're going to be arbitrary (which is inevitable) we might as well be arbitrary in a way that's easy to remember and hawks the Metric System. Might as well throw in a mass of 10^22 kilograms while we're at it; Pluto barely passes that test too.

This analogy has been raised before, but the argument about whether Pluto and this new object ought to be called planets or asteroids is reminiscent of the old question about whether Australia should be called an island or a continent. (It might be more appropriate to substitute Greenland for Australia, in this case, though.)

I can't speak for anybody else, but to me the most interesting about this new trans-Neptunian thingamabob is its 44-degree orbital inclination. Could it have accreted in an orbit like that? My semi-educated guess is that it couldn't, which implies it's been tossed there by something more massive. Does that mean that the Big Prize is still out there? Maybe the same thing responsible for the 50-AU cutoff of the Kuiper Belt? Could something that big and that close in have remained undiscovered until now?
Decepticon
With all these discovers which web page has a list of these objects?
Myran
QUOTE
Alan Stern said: That day will come, in this century. And so what of it? School children aren't expected
to know the names of all the stars, and no one claims we should arrange the definition of stars (or galaxies, etc.) just to keep the number of them small.


You took me a bit to literally there. biggrin.gif
My point is that I dont really think that the larger KBO's eventually wont be seen as anything else but just objects of the 'Kupier belt' even if we happen upon even larger ones. This is just a repetition of what happened when the asteroids were discovered, the first ones were viewed as planets then also. With more knowledge the perception of things will change.
Mongo
QUOTE (BruceMoomaw @ Jul 30 2005, 11:42 AM)
Personally, I still favor
setting a maximum diameter of 2000 km as the arbitrary planet/nonplanet
dividing line, which will allow Pluto to retain its longtime seat in the
Planet Club without allowing too many newcomers to crash the party.


It now looks like 2003 FY9 is bigger than originally reported. The original MPEC circular listed H = 0.1, but its absolute brightness was increased today to H = -0.4 (compared to Pluto at H = -0.5).

Given any plausible albedo, this would also mean a diameter in excess of 2000 km.

So we now know of three TNOs with diameters greater than 2000 km:

2003 UB313 H = -1.1 D = 2600-3200 km
Pluto H = -0.5 D = 2390 km
2003 FY9 H = -0.4 D = 2200-2500 km (personal guestimate)

Plus five more TNOs (counting Pluto's moon Charon) in the 1200 to 1600 km range:

2003 EL61 H = 0.3 D = ~1600 km
Charon H = 1.2 D = 1270 km
Sedna H = 1.6 D = ~1600 km
90482 Orcus H = 2.3 D = ~1500 km
50000 Quaoar H = 2.6 D = ~1300 km

I have a feeling that we will be finding a great many objects with diameters greater than 2000 km in the coming years. My own opinion is that we need to either set the dividing line for 'major planet' status higher -- a minimum diameter of 4000 km would allow Mercury to remain a major planet, while keeping the number of trans-neptunian major planets to a minimum -- or to abolish the distinction altogether.

Bill
gpurcell
I wonder if a size+orbital mechanics might not be a way to proceed. It strikes me that the inclination/highly elliptical nature of the orbits of the TNO class will end up being one of the key elements of differentiation. Set Pluto as an lower limit for mass and size, but also require that they be within a certain number of degrees within the solar plane AND that their orbits be no more elliptical than Pluto's if they are to be considered planets.
alan
QUOTE (Decepticon @ Jul 30 2005, 03:52 PM)
With all these discovers which web page has a list of these objects?
larger objects listed here, out of date now
http://www.ifa.hawaii.edu/faculty/jewitt/kb/big_kbo.html
all objects listed here
http://cfa-www.harvard.edu/iau/lists/TNOs.html
http://cfa-www.harvard.edu/iau/lists/Centaurs.html
alan
interesting note: 2003 EL61 has been found on plates from 1955, now part of Palomar digitized sky survey
I believe this is it at RA 10 09 55.6 Dec +24 51 40
http://www.ledas.ac.uk/staging/dss/dss0ef7_1.gif
dvandorn
Truthfully, I think that Pluto needs to be demoted to a KBO, and the rest of these objects need to be classified as KBOs. Regardless of size and mass. I think it's obvious that the KBOs, as a class, were formed rather differently from the rest of what we think of as planets -- most specifically, since they do not orbit in the plane of the ecliptic, they could not have been formed primarily from the solar nebula, since those nebulae always seem to array themselves in fairly thin disks.

I think that planets should be defined as objects that accreted directly from the solar nebular disk (defined by its orbital inclination) *and* that are larger than "X" in size and/or mass. Everything else, regardless of size and/or mass, should be defined as a KBO or an Oort cloud object (OCO).

So, simple rule -- formed from within the planetary disk = planet, formed outside of the disk = other.

-the other Doug
Alan Stern
QUOTE (gpurcell @ Jul 30 2005, 05:24 PM)
I wonder if a size+orbital mechanics might not be a way to proceed.  It strikes me that the inclination/highly elliptical nature of the orbits of the TNO class will end up being one of the key elements of differentiation.  Set Pluto as an lower limit for mass and size, but also require that they be within a certain number of degrees within the solar plane AND that their orbits be no more elliptical than Pluto's if they are to be considered planets.
*



This idea is unworkable. If an Earth were discovered in a high inclination orbit, would it
not be a planet? Of course not. Location (orbital or otherwise) is for realtors. Planethood
is about what KIND of object it is. (By the way, I note that no one says a star should be
befined by its orbit, or even if it is in a galaxy or not-- it is defined by what KIND of
object it is. It is just such a definition that we seek for lanets.)
Alan Stern
I think that planets should be defined as objects that accreted directly from the solar nebular disk (defined by its orbital inclination) *and* that are larger than "X" in size and/or mass. Everything else, regardless of size and/or mass, should be defined as a KBO or an Oort cloud object (OCO).

So, simple rule -- formed from within the planetary disk = planet, formed outside of the disk = other.


I'm sorry to say it, but this won't work etiher. I am on the IAU committee
looking into planetary nomenclature and one thing we defintiely agree on is
that formation mode is not a good way to go. Why? Because we won't
be able to determine an object's oriigin from things we observe-- this
problem is particularly acute for extrasolar planets.

And as to Sedna and Pluto and UB313, as best we can tell, they were accreted just
like Earth, Mars, etc., but aborted early in their growth. They were then ejected
to these oddball orbits, so in fact it does seem that these dwarf planets were
made just like Earth, and Mars, and Venus, but they ran out of feedstock for
one reason or another and ended up stunted.



And
dvandorn
Aw, shoot -- and here I had in mind a concept whereby these out-of-plane objects could be classified based on a certain degree of extra-solar composition. I had this image of the objects in the Kuiper Belt and Oort Cloud being condensed out of the interaction between the T-Tauri stage of the solar wind and the supernova remnant gasses and particles into which this energetic solar wind slammed... as such, they would be of a compositional mix between the solar nebula and the surrounding supernova nebula from which the Sun and its planetary nebula evolved.

Since the T-Tauri stage of the solar wind would have pushed out in all directions, it would have established a spherical structure around the Sun of the remnants of the interactions between the wind and whatever it pushed into and through on its way out. That would seem to be the perfect structure from which to derive the KBOs and OCOs, would explain why they occupy a space defining a spherical cloud around the Sun, and would suggest that these objects might be of somewhat different composition from the rest of the solar system.

Granted, all of this extrasolar material ought to similar to the materials derived from the planetary nebula, since the solar system was formed from a piece of the original supernova nebula. But it was my thinking that the extrasolar gasses and ices included in the KBOs and OCOs could let us characterize differences between the planetary nebula (from which the solar system was derived) and the surrounding supernova remnants. Isotopic abundance information would be extremely interesting, I bet...

But if all of these objects were originally formed from the planetary nebula disk and were later ejected into this spherical cloud, then my theory is non-applicable... darn it!

-the other Doug
Mongo
I do rather like Mike Brown's definition of a planet as an object, by far the largest in its own neighborhood. in a solitary orbit (not part of a recognised population of objects). I am copying an extract from his definition at:

http://www.gps.caltech.edu/~mbrown/sedna/

Just like the solar system very naturally divides itself between round objects and non-round objects, it also very naturally divides itself between solitary individuals and members of large populations. The best known example of a large population is the asteroid belt. We call it a population because one region of space contains objects with a continuous range of sizes from one moderately large object (Ceres) to a handful of slightly smaller objects (Vesta, Pallas, Hermione) to a huge number of extremely small objects (rocks, dust particles). The solitary individuals are much different. In their region of space there is only them (Earth, say) and then a collection of much much smaller objects (the near-earth asteroids), with no continuous population in between. A single example helps to dramatize the difference between a continuous population and a solitary individual. Ceres, the largest asteroid, has a diameter of 900 km. The next largest asteroid, Pallas, has a diameter of 520 km. After that is Vesta at 500 km, and Hygiea at 430 km, and the list continues on down. The jump in size between asteroids is never more than a factor of two. In contrast, the earth has a diameter of about 12,000 km, while the largest other object in the earth's vicinity, the asteroid Ganymed, has a diameter of about 41 km, a factor of 300!

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune all count as solitary individuals by this definition. Pluto and Quaoar do not. Pluto is clearly a member of the Kuiper belt population, as can be seen from the fact that there are objects in the same vicinity slightly smaller than Pluto (Quaoar, 2004 DW, Varuna), and then even a larger number slightly smaller than that, and then on down.


[...]

Since there is a clear scientific distinction between solitary individuals and members of large populations it is instructive to come up with words to describe these objects. The large populations can each be described by the particular population (asteroid belt, Kuiper belt, inner Oort cloud, Oort cloud). What about the solitary individuals? Isn't the best word to describe them "planet"?

[...]

Is there any historical basis for saying that a planet is a solitary individual that is not a member of a large population? Yes! As mentioned earlier, historically Ceres and the first few asteroids were initially classified as planets. Only when it became known that there were many many asteroids in similar orbits was it decided that they should no longer be classified as planets. Historically, there is a clear distinction between planets and populations. Any definition which fails to make this distrinction is in strong trouble on historical grounds. This simple look at history shows that Pluto is completely analogous to Ceres. Pluto was initially thought to be a solitary individual. Over time we found more objects in the vicinity and realized instead that it is a member of a large population. Historically, then, Pluto, too, should no longer be considered a planet.

We are thus left with a final concept of the word planet. Every object in the solar system quite naturally can be classified as either a solitary individual or a member of a large population. The individuals are planets. The populations are not. This definition fits the historical desire to distinguish between asteroids and planets, and this definition fits all of the requirements of scientific motivation.


Bill
BruceMoomaw
"In contrast, the earth has a diameter of about 12,000 km, while the largest other object in the earth's vicinity, the asteroid Ganymed, has a diameter of about 41 km, a factor of 300!"

Yeah, but now you have to define "vicinity". Are Mercury, Venus and Mars in Earth's "vicinity" or not? Conversely, let us suppose that the Kuiper Belt actually consisted of exactly one solar-orbiting object in a really weird orbit vastly different and very distant from the eight previously recognized planets -- but that object was only 3 feet across. Would it therefore be labeled a "planet"? I think not.

We really need to face facts: ANY criterion we use to try to define "planet" -- or "moon" -- will be crammed with unavoidable ambiguity and arbitrariness. (It's also increasingly clear that the same thing applies to our attempt to firmly separate "asteroids" from "comets", at least when the possible comets are so far from the Sun that no material is sublimating off them to allow us to tell how much of them is ice and how much is rock.) The situation is entiely different from the star/brown dwarf/planet distinction, where we do have a nice firm divider: brown dwarfs are big enough to fuse deuterium but not big enough to fuse regular hydrogen.
Myran
QUOTE
Alan Stern said: And as to Sedna and Pluto and UB313, as best we can tell, they were accreted just like Earth, Mars, etc., but aborted early in their growth.


Isnt that true for the asteroids also? In that case the most popular theory seems to be that the interaction with Jupiter prevented further growth, but the asteroids still had started on the same accretion process.
While talking about the asteroids one can note that 2003 UB313 have an inclination of 44% to the ecliptic, and that fact makes me think of one asteroid again and thats the 35 degree inclination of Pallas.

That Pluto have a moon have been used as part of the argument to keep its planetary status, but again, both asteroids as KBO's have turned out to have secondary objects as well.

I was beaten by Mongo on the last part of this reply, and that is that planets are solitary bodys in their orbits, whereas the asteroids belong to a group. The same appear to be true for the KBO's.

So the bottom line before I make my final post to this discussion are that whats said above are the reasons I found the declaration that 2003 UB313 is a 'newly discovered planet' to be quite inappropriate.
Jyril
In my opinion, large Kuiper Belt objects (including Pluto) do not qualify as planets. However, it sounds awkward to call them asteroids, because a typical asteroid/KBO is just a mostly unalterd chunk of rock or ice. Instead of asteroids, at least some of these larger bodies have much more complex geological histories and internal structures. Instead, there should be some term to define those miniplanets.

Someone (was it Brown?) proposed that they should be called "planetoids". Nobody really uses that term for asteroids anymore, and it describes them nicely as "planet-like".
Alan Stern
Bill--
You're back to that old location argument, which realtors like but few scientists do.
(Yes,Mike Brown is one of the ones who does, to my amazement.).

A real problem with the argument you like is that "a planet" is just the biggest thing
around., and nothing more. That means a planet has no properties other than mass.
So would a big spaceship (I mean BIGGGGG) count? How about a star? A black hole
in a planetary system? By the definition Brown expouses, they would be planets.

And even if you rule these out by demaning it be naturally created and not doing
fusion for a living, you have two other problems to overcome. First, as we learned in
the 1990s, migration is a very important dynamical process for planetary systems--
i.e., objects move about, particularly early and late in the evolution of the system
(when the parent star is young and when it is a red giant).

This kind of movement can cause Earths to move from orbits like ours to be Jupiter
crossing-- would that suddently cause Earth to be declassified as a planet in your
fave scheme. To me this is patentely undesirable. Worse, you say you want to
classify objects as to whether or not they are an individual or part of a big population,
but Earth is embedded in the NEA and Jupiter carries with it about 10^5 Trojans, so
neither is an individual at all.
BruceMoomaw
Back in the 1980s, Isaac Asimov proposed that comet nuclei be renamed "cometoids". This didn't catch on, but it would seem to be one promising approach to the KBO nomenclature problem -- except that, without getting very good analyses of their compositions, we genuinely can't tell whether objects far enough from the Sun to be frozen are made mostly out of ice or rock, and dynamics simulations suggest that several percent of KBOs really may be rocky asteroids that wandered out of the inner System.
Mongo
QUOTE (Alan Stern @ Jul 30 2005, 10:25 PM)
This kind of movement can cause Earths to move from orbits like ours to be Jupiter
crossing-- would that suddently cause Earth to be declassified as a planet in your
fave  scheme. To me this is patentely undesirable. Worse, you say you want to
classify objects as to whether or not they are an individual or part of a big population,
but Earth is embedded in the NEA and Jupiter carries with it about 10^5 Trojans, so
neither is an individual at all.

Well, if Earth were put into a Jupiter crossing orbit, it would presumably either eventually collide with it, or be ejected from the solar system, and in either case, the issue of whether it was a planet would not arise. *grins*

According to Mike Brown's suggested definition, the presence of a population of much smaller objects in the vicinity of a much larger object does not affect the much larger object's 'major planethood' status, so neither NEOs (in the case of Earth) nor Jupiter Trojans (in the case of Jupiter) are relevant to their status as major planets, as there is a major difference in diameter and mass.

I would also discount trojan objects as being true planets, whatever their size, as they are clearly in a close dynamical relationship with their 'primary' -- not as directly as with a satellite, but still tied to its gravitational influence. In any case, the maximum stable mass of a trojan would be well below the mass of its 'primary', if I am not mistaken.

Having said all this, I am not married to Brown's definition either. It should be possible to cobble together something that works for our planetary system, but it will be harder to come up with something that works for all planetary systems. Heck, I am no fan of the current nomenclature for naming extrasolar planets! Talk about illogical...

This is getting off-topic, but the current system is crazy. In multi-planet systems, we are seeing that the planets are given letters in the order of their discovery, which leads to random orders within the planetary system. I think that A, B, C should be restricted to stars, as they had been for decades. With the planets so far discovered, the one datum almost always found, other than their mere existence, is their orbital period -- and even when the exact period is not yet known, it can be estimated. Why not tie the planet name to that? I am thinking in particular of using the common logarithm of the planet's orbital period in days, so that (for example) a planet, orbiting HD 123456, with a period of 3.2 days, would be called HD 123456 p05, and its neighbor with a period of 800 days would be called HD 123456 p29.

For a specific example, take the 55 Cnc system:

55 Cnc E -- p = 2.81 days
55 Cnc B -- p = 14.67 days
55 Cnc C -- p = 43.93 days
55 Cnc D -- p = 4517.4 days

This could be changed to:

55 Cnc p04
55 Cnc p12
55 Cnc p16
55 Cnc p37

Which would have the advantage that the planets in a planetary system would always be sortable by period (and semimajor axis), with no other information needed other than their designations.

I doubt that it will ever happen, though, as the current system of nomenclature has become fairly well-established, despite its evident flaws.

Bill
BruceMoomaw
QUOTE (Mongo @ Jul 30 2005, 04:09 PM)
It now looks like 2003 FY9 is bigger than originally reported.  The original MPEC circular listed H = 0.1, but its absolute brightness was increased today to H = -0.4 (compared to Pluto at H = -0.5).

Given any plausible albedo, this would also mean a diameter in excess of 2000 km.

So we now know of three TNOs with diameters greater than 2000 km:

2003 UB313  H = -1.1  D = 2600-3200 km
Pluto  H = -0.5  D = 2390 km
2003 FY9  H = -0.4  D = 2200-2500 km (personal guestimate)


Bill
*


Where'd you get this information, Bill? It isn't yet in the Minor Planet Electronic Circulars.
BruceMoomaw
By the way, it's "2005 FY9", not "2003 FY9".
Mongo
QUOTE (BruceMoomaw @ Jul 30 2005, 11:25 PM)
Where'd you get this information, Bill?  It isn't yet in the Minor Planet Electronic Circulars.

There was a post at mpml today from SFJCody that the newest MPEC daily orbit update gives an H value of -0.4 for this object (yes it is 2005 FY9, of course -- mea culpa). The circular is here, and the changed information is about 3/4 of the way down the list:

K05F06F 16.8 0.15 K058I 89.885 323.875 169.168 3.014 0.06214 2.26700 3 X
K05F07Q 17.0 0.15 K058I 42.784 15.107 157.245 14.384 0.18256 2.69019 2 X
K05F09Y -0.4 0.15 K058I 199.428 256.589 79.412 28.999 0.14117 45.58983 2 X
K05G13Y 14.7 0.15 K058I 316.249 203.539 89.030 12.347 0.13933 3.22548 2 X
K05G30F 15.8 0.15 K058I 294.161 232.095 77.869 6.996 0.11826 2.42330 5 X

Bill
deglr6328
Getting away from the planet/KBO/TNO debate for a minute....
huh.gif
do we have enough data yet on the KB region to make valid statistical guesses on the size distribution of the objects we're likely to find there? What about the Oort cloud? Is it reasonably possible to find a near Earth size object eventually? There was an idea from David Stevenson at Caltech in the late '90s that TOTALLY fascinated me and since then has always stuck in the back of my head when thinking about these (very) far out objects. He calculated that for ~Earth mass objects floating in interstellar space with Kbar surface pressures, liquid water oceans are possible. I often wonder if this idea can't be applied to large KBOs which we may (or very well may not?) find.
Alan Stern
These new guys are lilely to not be KB but instead Oort Cloud members. In any case,
there are very good arguments, I think, that there should be objects up to at
least Earth size, possibly a couple of times that, out there int he OC. See my 1991
paper: On the Number of Planets in the Solar System: Evidence of a Substantial
Population of 1000-km Bodies. Icarus, 91, p271, 1991. This paper predicts
both the find made today and much larger finds. One argument worth noting
for the really big guys is that to achieve the tilts of Uranus and Neptune, you need
collisions with objects of 2-5 Earth masses, and for every object that hit U and N,
several get ejected in near-miss collisions..
deglr6328
Cool! I will have to wait to read your paper in icarus when I get abck to work monday, where I have access. biggrin.gif
BruceMoomaw
In our little private "Planetary Sciences" webgroup, Ron Baalke quoted Mike Brown himself as saying yesterday: "Based on Spitzer measurements, 2005 FY9 is confirmed to be smaller than Pluto." Unfortunately, he didn't say how much smaller. But at any rate the Revolution is now upon us: depending upon what size you use as a dividing line, the Solar System no longer has 9 known planets. It now has 10 or 11, or else it has 8, or else (if you follow Alan Stern's lead) it has a hell of a lot more. What we are really going to have to tell the schoolkids, of course, is that the question from now on will be forever ambiguous.
Jyril
Like I feared, that -0.4 value was a false alarm, it's back at 0.1:

QUOTE
K05EA4J 15.3  0.15 K058I  50.368 152.552 353.444  8.943 0.04266  3.16664  3 X
K05EC4D 16.2  0.15 K058I 315.090 244.333  35.895  5.214 0.15325  2.56078  3 X
K05F09Y  0.1  0.15 K058I 146.099 296.739  79.519  28.999 0.15458  45.74014  6 X
K05G34P 16.3  0.15 K058I  8.979  97.234 142.622  12.137 0.24768  2.62499  4 X
K05J63S 15.8  0.15 K058I 355.253 102.910 178.954  25.752 0.27856  3.22140  3 X


I've read that 2005 FY9 could be 50%-75% Pluto's size.
OWW
In my opinion the whole planet/KBO/asteroid debate is the result of people still thinking like 18th century astronomers. Planets circle around the sun. Moons circle around the planets. Comets have tails and elliptical orbits around the sun. Predictable like a giant clock.

But we know now nature is not organized. There are only smaller and larger clumps of matter and their orbits are sometimes chaotic.

Therefore, the following questions can never be clearly answered.
When does an asteroid become a comet? When does a moon become a planet? When does a ring particle become a moon? When does a KBO become a planet? Is an object in a Lagrange point a moon or a planet?

The solar sytem how I see it:
- The Sun: star ( fusion )
- The rest: 'worlds' ( from dust spec to Jupiter )
- Gas giants: asteroids ( star like worlds, no solid surface )
abalone
What peculiar little creatures we humans are that we find it necessary to have everything assigned to its correct pigeon hole. I cant see the slightest relevance to this decision as to whether we call it a planet or not. " It orbits, therefore it is" and "A rose by any other name would smell as sweet"
dilo
Based on the ongoing discussion, I made following flow diagram in order to adress main objection rised up to now.
Click to view attachment
This general method should correctly discriminate between a natural satellite (a planet if central body is a star or a moon for an object orbiting a planet) and a planetoid/”satelloid” isolated or belonging to a wide population like asteroids belt or KB.
Obviously, this is only a sketch and numerical constraint on radius and semi-major orbit can be revised... Anyway, I deribely avoided to use absolute measures (like size in Km) in order to have a general method that can apply also to planet/moons systems. Obviously, these pure numbers are choosen in order to include all solar system planets; inclusion of Pluto and other major KBO could be temporary, because it depends on future discovery of other objects with similar orbit. This is the normal historical process higlighted by Alan...
Alan Stern
Dilo--I wonder, what will you do when Mars-sized and larger objects are found in the
Oort Cloud on highly elliptccal orbits that range over the same distance from the Sun?
Classify ejected Mars- and Earth-sized bodies as planetoids? And what about in
extra-solar planetary systems in formation where one routinely expects very large
bodies (Mercury to Uranus sizes) on crossing orbits? Can only the single largest
one be a planet? If an object is small compared to its neighbors but ejected to
a place where it is large compared to its new neighbors, does it get promoted
to planethood just by virtue of lits change in location? If the reverse happens,
do you propose the object be demoted, as the flowchart algorithm suggests
one would have to do?

Localtion and relative-size arguments always have these problems. Planets are planets
because of what kind of body they are. I remain convinced it is better to pick a good
criteria-- like being rounded by gravity-- and let the number of bodies be whatever
Nature delivered.

-Alan
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