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[Chicago Astronomer - Astro Joe]

Pluto Could Lose Planet Status

At its conference this August, the International Astronomical Union (IAU) will make a decision that could see Pluto lose its status as a planet.

For the first time, the organisation will be officially defining the word "planet", and it is causing much debate in the world of astronomy.

There is only one thing that everyone seems to agree on: there are no longer nine planets in the Solar System.

The debate has been brought to a head by the discovery of a potential 10th planet, temporarily named 2003 UB313 in January 2005. This new candidate planet is bigger than Pluto.

The question now facing the IAU is whether to make this new discovery a planet.

Pluto is an unusual planet as it is made predominantly of ice and is smaller even than the Earth's Moon.

There is a group of astronomers that are arguing for an eight-planet SolarSystem, with neither Pluto or 2003 UB313 making the grade as a planet; but a number of astronomers are arguing for a more specific definition of a planet.

One of these; Kuiper Belt researcher Dr Marc Buie, of the Lowell Observatory in Arizona, has come up with a clear planetary definition he would like to see the IAU adopt.

I believe the definition of planet should be as simple as possible, so I've come up with two criteria," he said.

"One is that it can't be big enough to burn its own matter - that's what a star does. On the small end, I think the boundary between a planet and not a planet should be, is the gravity of the object stronger than the strength of the material of the object? That's a fancy way of saying is it round?"

This definition could lead to our Solar System having as many as 20 planets, including Pluto, 2003 UB313, and many objects that were previously classified as moons or asteroids.

One possible resolution to the debate is for new categories of planet to be introduced. Mercury, Venus, the Earth and Mars would be "rocky planets". The gas-giants Jupiter, Saturn, Uranus and Neptune would be a second category.

Whatever the outcome of this debate there is only one thing that we can be certain of; by September 2006 there will no longer be just nine planets in our Solar System.

Story here: www.physorg.com/news70120085.html

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It is indeed a complicated issue and far from clear cut. I vote "Yes" for planet status for Pluto. It's round, got a satellite, and even tho it's orbit is skewed, it's regular. This will open up the field to other bodies, and our solar system is about to get new members.

The ancient Summarians wrote about 12 planets orbiting the Sun.

Could be...

[Chicago Astronomer - Astro Joe]

Astronomers struggle to define 'planet'

Should this newly found icy rock known as "2003 UB313" become the 10th planet? Should Pluto be demoted? And what exactly is a planet, anyway?

Ancient cultures regularly revised their answer to the last question and present-day scientists aren't much better off: There still is no universal definition of "planet."

That all could soon change, and with it science textbooks around this planet.

At a 12-day conference beginning Monday, scientists will conduct a galactic census of sorts. Among the possibilities at the meeting of the International Astronomical. "It's time we have a definition," said Alan Stern, who heads the Colorado-based space scienceastronomers

The debate intensified last summer when astronomer Michael Brown of the California Institute of Technology announced the discovery of a celestial object larger than Pluto. Like Pluto, it is a member of the Kuiper Belt, a mysterious disc-shaped zone beyond Neptune containing thousands of comets.

The discovery stoked the planet debate that had been simmering since Pluto was spotted in 1930.

Some argue that if Pluto kept its crown, Xena should be the 10th planet by default - it is, after all, bigger. Purists maintain that there are only eight traditional planets, and insist Pluto and Xena are poseurs.

"Life would be simpler if we went back to eight planets," said Brian Marsden, director of the astronomical union's Minor Planet Center in Cambridge, Mass.

Still others suggest a compromise that would divide planets into categories based on composition, similar to the way stars and galaxies are classified. Jupiter could be labeled a "gas giant planet," while Pluto and Xena could be "ice dwarf planets."

"Pluto is not worthy of being called just a plain planet," said Alan Boss, an astrophysicist at the Carnegie Institution in Washington, D.C. "But it's perfectly fine as an ice dwarf planet or a historical planet."

The number of recognized planets in the solar system has seesawed based on new findings. Ceres was initially classified as a planet in the 1800s, but was demoted to an asteroid. Despite the lack of scientific consensus on what makes a planet, the current nine - and Xena - share common traits: They orbit the sun. Gravity is responsible for their round shape. And they were not formed by the same process that created stars.

Brown, Xena's discoverer, admits to being "agnostic" about what the international conference decides. He said he could live with eight planets, but is against sticking with the status quo and would feel a little guilty if Xena gained planethood because of the controversy surrounding Pluto.

"If UB313 is declared to be the 10th planet, I will always feel like it was a little bit of a fraud," Brown said.

For years, Pluto's inclusion in the solar system has been controversial. Astronomers thought it was the same size as Earth, but later found it was smaller than Earth's moon. Pluto is also odd in other ways: With its elongated orbit and funky orbital plane, it acts more like other Kuiper Belt objects than traditional planets.

Even so, Pluto remained No. 9 because it was the only known object in the Kuiper Belt at the time.

When new observations in the 1990s confirmed that the Kuiper Belt was sprinkled with numerous bodies similar to Pluto, some scientists piped up. In 1999, the international union took the unusual step of releasing a public statement denying rumors that the ninth rock from the sun might be kicked out.

That hasn't stopped groups from attacking Pluto's planethood. In 2001, the Hayden Planetarium at New York's American Museum of Natural History unleashed an uproar when it excluded Pluto as a planet in its solar system gallery.

Earlier this year, NASA's New Horizons spacecraft began a 9 1/2-year journey to Pluto on a mission that scientists hope will reveal more about the oddball object.

The trick for astronomers meeting in Prague is to set a criterion that makes sense scientifically. Should planets be grouped by location, size or another marker? If planets are defined by their size, should they be bigger than Pluto or another arbitrary size? The latter could expand the solar system to 23, 39 or even 53 planets.

It's not an academic exercise - the public may not be open to a flood of new planets. Despite their differences, scientists agree any definition should be flexible enough to accommodate new discoveries.

"Science progresses," said Boss of the Carnegie Institution. "Science is not something that's engraved on a steel tablet never to be changed."

Source: www.physorg.com/news74703928.html

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I will bet that Pluto will remain as a planet.

[Maddad]

They should have "Kept it Simple, Stupid" Any object that has the name Mercury, Venus, Earth, Mars, Jupiter, Satury, Uranus, Neptune, or Pluto is a planet. With the decision they just came to, we've now got upwards of 53 planets. For crying out loud, Ceres is now a planet!

[Chicago Astronomer - Astro Joe]

The IAU Sees it The Chicago Astronomer Way...

#Yay#

We have all become comfortable with the established 9 planets we all grew up with, but I have absolutely no problem in allowing more to join the club.

My criteria has always been..."If it's round, orbits the Sun, and has an atmosphere of sorts, then it's a planet".

Why not include Ceres as a planet. It does fit the criteria on all points...and it was considered a planet in it's own right when discovered. If you follow the past threads on this subject, I think I made my preference clear and rational behind it. (Bribing the IAU was expensive!... )

My only question is why bring Charon on in. It's a Satellite of Pluto and orbits it.

[Chicago Astronomer - Astro Joe]

Pluto gets to remain a planet.

And the new definition also includes the three new planets encompassed by the group's definition -- the asteroid Ceres; Pluto's moon Charon; and an icy body beyond Pluto called 2003 UB313, unofficially known as Xena, which would belong to a class of planets to be known as "plutons."

For Ceres, it would be a belated promotion. By far the largest asteroid at 580 miles across, Ceres actually was called a planet when first discovered in 1801. But further findings of asteroids between the orbits of Mars and Jupiter led astronomers to class it with those smaller objects. A study last year of Hubble Space Telescope images proved that Ceres is round, placing it within the new definition.

Although Charon is called Pluto's moon, it was included in the new planet definition because many astronomers believe the two worlds comprise a "double planet" system. Pluto and Charon orbit each other, and their common center of gravity lies outside of Pluto, unlike any other planet-moon system. The existence of Xena was announced last year by Mike Brown, an astronomer at the California Institute of Technology, who also served on the IAU committee. Hubble images have shown the object is at least as big as Pluto. Brown and other experts believe there may be dozens of such worlds in an area called the Kuiper Belt, a mysterious, disc-shaped zone beyond Neptune containing thousands of comets and planetary objects. Pluto itself and two of the potential newcomers -- Charon and 2003 UB313 -- would be plutons.

Source: www.sun-sentinel.com/news/nationworld/sfl-aplanets16aug16,0,1301877.story?coll=sfla-news-nationworld

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I shows the limited mind set of the thinking when Ceres was discovered. Granted, they were not aware of it's spherical shape, so they just threw it in with the rest of the debris.

And good for Pluto!... ;D

[Chicago Astronomer - Astro Joe]

New Planets Shouldn’t Rock Your World

“It may end up that we have hundreds of planets in the solar system with this new definition,” Gerakines said. That shouldn’t scare schoolchildren all over the world. What will happen, if the proposal is adopted, is that the way we talk about planets will change. “Instead of just talking about planets, we’ll be talking about types of planets,” he said.

Gerakines is a member of the IAU but did not attend the Prague Conference. He reminds people who would panic over the changing definition of planets that 500 years ago, it was widely thought that the Earth was the center of the universe and that planets were merely “wandering stars.” The word “world” once meant “universe” until it was found by Galileo

“That’s the nature of science,” Gerakines said. “Science is about adapting our thinking according to what we observe in the universe.”

Source: University of Alabama at Birmingham is nothing to get concerned over, says UAB physics professor Perry Gerakines, Ph.D. Union (IAU) that would change the definitions of planets and add three planets to our that planets were similar to Earth. Nowadays, we know of many “worlds” such as ours.

Source: www.physorg.com/news75042989.html

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I have already read new memorization phrases and it's just just about as simple.

[Centaur]

The Trans-Neptunian Object preliminarily assigned the label 2003 UB313 has now been given the permanent designation Groucho. It was immediately informed that it is being considered for membership in the elite club of major planets. Groucho quickly declined, quipping, “I don’t care to belong to any club that will have me as a member.”

[Chicago Astronomer - Astro Joe]

In referren ce to the IAU's recent announcements:

" Why a 4-year-old child could understand this report. Run out and find me a 4-year-old child. I can't make head or tail out of it."

Groucho

I think the Marx brothers were witty, sharp and quite cool... ;D