Big Tno Discovery Options

[Mongo]

Recently, a nineteen-member committee of the International Astronomical Union (IAU) attempted to define "planet" and clarify whether Pluto and the tenth planet are really planets. However, the committee failed to reach a decision.

Committee members voted on three proposals. Each member was free to vote for more than one proposal.

The first proposal is the one children learn in school: the solar system has nine planets from Mercury to Pluto. This definition might imply that the tenth planet is also a planet, since it is larger than Pluto.

This proposal received eleven votes from the nineteen-member committee.

A second proposal suggested classifying planets according to type--for example, calling some of them terrestrial planets and others giant planets. Under this scheme, Pluto and the tenth planet would be considered trans-Neptunian planets, but so would several members of the Edgeworth-Kuiper belt that are smaller than Pluto.

This proposal received eight votes from the nineteen-member committee.

The third and final proposal said the solar system has only eight planets, those from Mercury to Neptune. Under this proposal, neither Pluto nor the tenth planet would qualify as planets.

This proposal received just six votes from the committee.

Okay, no wonder this committee is having so much difficulty coming to a decision -- they have significant problems with basic arithmetic!

11+8+6 = 19?

I suspect that either the votes for the first proposal are miscounted, since they would create a majority (of 11 out of 19 voters) for that proposal, or there are 25 voters on this committee.

Bill

[abalone]

Okay, no wonder this committee is having so much difficulty coming to a decision -- they have significant problems with basic arithmetic!

11+8+6 = 19?

I suspect that either the votes for the first proposal are miscounted, since they would create a majority (of 11 out of 19 voters) for that proposal, or there are 25 voters on this committee.

Bill

I think your answer is here

Committee members voted on three proposals. Each member was free to vote for more than one proposal.

[ljk4-1]

Kuiper Belt Moons Might Be More Common

Summary - (Wed, 18 Jan 2006) Just a few years ago, Pluto was considered unusual for Kuiper Belt Objects because it has a moon. Now three of the four largest KBOs have been discovered with moons, and it's causing astronomers to reconsider how this came about.

Only 11% of smaller KBOs have a moon, and probably captured them with gravity. But the moons for the larger objects likely formed when similarly-sized planetoids collided together, and the debris turned into their moons.

http://www.universetoday.com/am/publish/ku...ns.html?1812006

[SFJCody]

A planet definition from Alain Maury:
http://www.spaceobs.com/perso/textes/planetsandasteroids.htm

[ljk4-1]

Paper: astro-ph/0601414

Date: Thu, 19 Jan 2006 04:21:30 GMT (55kb)

Title: Exploring the surface properties of Transneptunian Objects and Centaurs
with polarimetric FORS1/VLT observations

Authors: S. Bagnulo, H. Boehnhardt, K. Muinonen, L. Kolokolova, I. Belskaya,
M.A. Barucci

Comments: 11 pages, 7 postscript figures, accepted by A&A
\\
Polarization is a powerful remote-sensing method to investigate solar system
bodies. It is an especially sensitive diagnostic tool to reveal physical
properties of the bodies whose observational characteristics are governed by
small scatterers (dust, regolith surfaces). For these objects, at small phase
angles, a negative polarization is observed, i.e., the electric vector E
oscillates predominantly in the scattering plane, contrary to what is typical
for rather smooth homogeneous surfaces. The behavior of negative polarization
with phase angle depends on the size, composition and packing of the
scatterers. These characteristics can be unveiled by modelling the light
scattering by the dust or regolith in terms of the coherent backscattering
mechanism.

\\ ( http://arXiv.org/abs/astro-ph/0601414 , 55kb)

[SFJCody]

A planet definition from Parade magazine:

http://www.parade.com/articles/editions/20...ce_Tenth_Planet

[dvandorn]

That is, no more or less, exactly what Alan has posted here as *his* definition of a planet.

Well, at least they swiped their definition from an authoritative source.

-the other Doug

[SigurRosFan]

2003 UB313 is much smaller.

- http://sciencenow.sciencemag.org/cgi/content/full/2006/127/1 - Downsizing the "Tenth Planet"

--- That's surprising, Brown said, because it means that the object reflects a remarkable 92% of the light that hits it--compared with roughly 60% for Pluto. "I had expected it to be darker and considerably larger," Brown said. Geysers may continually coat the surface with fresh frost, he speculated, although how that occurs on such a frigid body is unknown.

However, a chart of 2003 UB313's projected size on Brown's Web site indicates that with a reflectivity of 92%, the object would be roughly 1% larger than Pluto's assumed diameter of 2280 kilometers. The team's previous estimates had ranged from 25% larger (on its Web site) to 50% larger (at NASA's announcement in July). ---

[SFJCody]

2003 UB313 is much smaller.

- http://sciencenow.sciencemag.org/cgi/content/full/2006/127/1 - Downsizing the "Tenth Planet"

--- That's surprising, Brown said, because it means that the object reflects a remarkable 92% of the light that hits it--compared with roughly 60% for Pluto. "

http://www.foothill.fhda.edu/ast/news.htm#Anchor5

Well, this is interesting. I wonder how large the error bars on that figure are? And when is this NASA press conference mentioned in the article going to be held?

[Decepticon]

And when is this NASA press conference mentioned in the article going to be held?

Good question! I hate missing Live press conferences!

[ljk4-1]

Astrophysics, abstract
astro-ph/0601654

From: Eugene Chiang [view email]

Date: Fri, 27 Jan 2006 21:49:32 GMT (150kb)

A Brief History of Trans-Neptunian Space

Authors: E. Chiang (UCB), Y. Lithwick (UCB/CITA), R. Murray-Clay (UCB), M. Buie (Lowell), W. Grundy (Lowell), M. Holman (Harvard CfA)

Comments: Refereed, accepted, formatted review chapter for Protostars and Planets V compendium

The Edgeworth-Kuiper belt encodes the dynamical history of the outer solar system. Kuiper belt objects (KBOs) bear witness to coagulation physics, the evolution of planetary orbits, and external perturbations from the solar neighborhood. We critically review the present-day belt's observed properties and the theories designed to explain them. Theories are organized according to a possible time-line of events. In chronological order, epochs described include (1) coagulation of KBOs in a dynamically cold disk, (2) formation of binary KBOs by fragmentary collisions and gravitational captures, (3) stirring of KBOs by Neptune-mass planets (``oligarchs''), (4) eviction of excess oligarchs, (5) continued stirring of KBOs by remaining planets whose orbits circularize by dynamical friction, (6) planetary migration and capture of Resonant KBOs, (7) creation of the inner Oort cloud by passing stars in an open stellar cluster, (8) in situ coagulation of Neptune Trojans, and (9) collisional comminution of the smallest KBOs. Recent work underscores how small, collisional, primordial planetesimals having low velocity dispersion permit the rapid assembly of ~5 Neptune-mass oligarchs at distances of 20-40 AU. We explore the consequences of such a picture. We propose that Neptune-mass planets whose orbits cross into the Kuiper belt for up to ~40 Myr help generate the high-perihelion members of the hot Classical disk and Scattered belt. By contrast, raising perihelia by sweeping secular resonances during Neptune's migration might fill these reservoirs too inefficiently when account is made of how little primordial mass resides in bodies large enough to be observable. These and other frontier issues in trans-Neptunian space are discussed quantitatively.

http://arxiv.org/abs/astro-ph/0601654

[SigurRosFan]

New results:

New "planet" is larger than Pluto:

Bonn astronomers measure size of newly discovered solar system object

- http://www.astro.uni-bonn.de/~bertoldi/ub313/

The size measurement of 2003 UB313 is published in the 2 February 2006 issue of Nature. Xena is now 3,000 +/-300 kilometers (Albedo 0.6) wide.



Very interesting:

--- Note on reports of an HST size measurement (31.1.)

Mike Brown gave a public talk recently where he presented some preliminary results on an attempt to measure the size of UB313 with the Hubble Space Telescope [Albedo 0.92 news]. A journalist picked this up and reported it, against Mike Brown's explicit request. In response to this report Mike Brown stated on Jan 31:

"Contrary to rumors otherwise, we're just in the preliminary stages of analyzing the HST data. When we are done we should have a very precise measurement. The study that is coming out in Nature is the best info that we have for now about how big and reflective it is. The uncertainties are large, but it seems a solid result to me. I hope that we will have the HST analysis done within perhaps a month, and I'll be able to say more then." ---

[alan]

Brown's webpage has an update on progress on deciding whether 2003 UB313 is a planet or not

The above gives my personal view on how to resolve the planetary status. The official decision will come from the International Astronomical Union. We had hoped for a timely decision but we instead appear to be stuck in committee limbo. Here is the story, as best I can reconstruct it from the hints and rumors that I hear:

    *  A special committee of the International Astronomical Union (IAU) was charged with determining "what is a planet."
    * Sometime around the end of 2005, this committee voted by a narrow margin for the "pluto and everything bigger" definition, or something close to it.
    *  The exectutive committee of the IAU then decided to ask the Division of Planetary Sciences (DPS) of the American Astronomical Society to make a reccomendation.
    * The DPS asked their committee to look in to it.
    * The DPS committee decided to form a special committee.
    * Rumor has emerged that when the IAU general assembly meets in August in Prauge they willl make a decision on how to make a final decision!

So when do we expect a decision? Back in August 2005 I used to joke that the IAU was so slow they might take until 2006 before deciding. That was supposed to be a joke. Now I joke that I hope there is a decision by the time my daughter starts grade school and learns about planets in class. She is currently 7 months old.

[SFJCody]

http://www.newscientistspace.com/article.ns?id=dn8681

[David]

http://www.newscientistspace.com/article.ns?id=dn8681

You know, planets were being defined and undefined and given names long before the IAU existed. If the IAU insists on sitting on its hands for years and years, I think that astronomers and astronomy-buffs ought to take matters into their own hands and simply adopt a solution. I suspect that the IAU committee have just been thinking too hard about the question. I recommend a solution that required almost no thinking at all :

My solution is:
Our solar system has ten planets; they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and Proserpina.

The minimal amount of thought that went into it was this:

Pluto has been accepted as a planet for 76 years and that is unlikely to change regardless of what the IAU thinks;
If Pluto is a planet, there is no reason for 2003 UB313 not to be a planet, since it goes around the sun and is bigger than Pluto;
Therefore 2003 UB313 will be accepted as a planet.

I use the name Proserpina, because even though it wouldn't be my first choice for the name, discoverer Mike Brown has favored either Persephone or Proserpina, and Latin forms are preferred for planets.

Edit: I should add that the only way that this represents my private view is that I want to see the nonsense cut through and a decision finally arrived at. I think that this is likely to be what happens at the end of the argument anyway, and I'd rather have it happen immediately than in two, three, or five years' time. I'd be just as happy with a decision that a body has to be at least as big (or as massive) as Mercury in order to be a planet.