Not exactly. When you have Pluto now regarded as a "Dwarf Planet," but not a true "Planet," then something is wrong. When you have a growing number of Solar System bodies being discovered that have all the qualifiers of a "Planet," yet are not granted that recognition, but are instead referred to in a general way as KBOs (Kuiper Belt Objects) just to avoid giving them the deserved title of "Planet," the general discomfort grows. Some say it's a silly dispute, but its resolution will impact an entire science.
Look at the second part of the statement. It’s a performance criteria related to how it interacts with other terrestrial bodies that intersect it’s orbit. If you call it a planet, you may have to call 200 plus other bodies in the solar system that fit this criteria. . It’s not our decision. We need to get over it. “The International Astronomical Union defines a planet as being in orbit around the sun, has enough gravity to pull its mass into a rounded shape (hydrostatic equilibrium), and has cleared its orbit of other, smaller objects. This last criterion is the point at which planets and dwarf planets differ. A planet's gravity either attracts or pushes away the smaller bodies that would otherwise intersect its orbit; the gravity of a dwarf planet is not sufficient to make this happen. [Meet the Dwarf Planets of the Solar System]
The IAU's definition of a planet is not functional, and needs to be changed. First of all, basing all our definitions on our own Solar System has ALREADY proven ineffective and problematical. We've now discovered over 4,000 other planetary systems around other stars, and none of them match the parameters of our own. So, definitions have to be revised to match interstellar realities more accurately. I repeat. . .planets should be defined by these parameters: 1. they are not a star; 2. they orbit a star; 3. they are massive enough to retain a spherical shape; and possibly 4. they aren't comets. The IAU's qualifier that they must have cleared their orbits of debris introduces problems for us. First, our first & recent photos of Pluto showed that it's been literally hundreds of thousands & possibly several millions of years since anything large enough to make a substantial impact crater actually did so on Pluto. That is evidence that Pluto probably has cleared its orbit of debris substantial to warrant being re-designated a planet. This opens up that same possibility for the other KBO's already discovered, and possibly those still waiting for discovery, to become planets in their own right. Who knows what's out there in the Oort Cloud? Second, many of the recently discovered planetary systems around other stars don't conform to the IAU structure for defining planets. Some are in theiir early or mid development stages, and are proto-planets. But proto-planets are still "planets"--just very young ones. Are we going to come up with individualized new groupings for all those new exo-planets that are multiplying like rabbits on our discovery logs? If they're not planets, what are they? How can we decide until we have instruments capable of resolving their orbit with enough detail to determine whether it's sufficiently clear of debris to confer the title of planet on it? What a nightmare. Any entity that conforms to my definition above should be regarded as a planet, regardless of where it is, in our Solar System or orbiting another star. We can still have "dwarf planets," if you wish, but it should be a sub-group of "Planet."
With the onslaught of new exo-planetary discoveries almost daily, the IAU needs to amend it's consciousness to reach beyond the Solar cradle.
As this is not within their mandate, it is likely they will not be tapped to do so and the naming/designation of extrasolar objects will continue as is. The system in place functions well and as the details of extrasolar bodies cannot be observed there is not sufficient data to go further and complicate the process.
Well, unless you have a degree in astrophysics which I don’t, I suggest we leave it to the people and institutions that really ‘ know” why Pluto has been renamed. Part of being a good scientist is knowing what you don’t know and depending upon accepted conclusions by consensus for that. I see a lot of conclusions but NO REFERENCE. Saying the IAU has a bogus definition requires more then your opinion without a reference from an equally accepted organization. That’s the way science works.....and it’s not, just trying to copy other opinions without a reference.
You make some good points. You & I can't resolve the question. Only the IAU has that authority. But it was a fun discussion.
I didn't. I just highlighted the part I wanted to comment about and it came up with a choice to quote or reply. It's the software. I did nothing, but what it allowed. Actually, highlighting(changing text to bold font) any part of your post is editing. I don't know if you noticed, but the software also puts a little arrow on the left part of the quote which will take you back to the original post. I'll try to remember your request. My memory is not so good, though, and if the software allows, it isn't an offense, nor was it intended as one. Why are you sensitive to that?
By the way, it IS a size thread, since Pluto was removed from planet status because it is smaller than a newly discovered rock in the same Kuiper Belt. Neptune is it's inner boundary. Is Neptune really a planet? It's bigger than Pluto. Sorry, that darn size thing keeps coming up.
I still say the first question to answer is 'what is the purpose' of naming objects a planet? If we say a planet has a circular orbit then that leaves out Planet X or Nibiru. If we go solely by spherical and a certain size then 'what size'? How many more objects will be found that are larger than Pluto? Is everything in the Kuiper Belt a non-planet? If a planet has cleared it's area of other stuff, I suppose ignoring moons, how large of an area must be cleared? Is a dwarf planet also a planet?
Yeah so a paper by a guy arguing Pluto is a planet doesn't validate the thread title that "Pluto is to be re-planetized."
Pluto's old news . . . now it's Mercury, here we come! Which reminds me - I wonder what happened to the 'probe' which was sent to find out 'how the sun works'? Probably drifting out there in the 'verse somewhere as a lump of molten metal. What a waste of money.
To me, a "planet" is as follows: 1. it's not a star; 2. It orbits a star; 3. It's massive enough to maintain a spherical shape; 4. It's not a comet. Any object fulfilling these criteria should be a planet. However, there can be a wide variety of planet types. For example, we can have rocky planets, gas planets, dwarf planets, terrestrial (Earth-like) planets; gas giant planets, exo-planets, proto-planets, etc. I strongly disagree with the IAU definition requiring a "planet" to have already cleared its orbit of residual bodies. This is both too hard to determine accurately, and would automatically discount planets in the stages of formation around a young star. The IAU also defined a "planet" as a body that orbits "the Sun." We now know of over 3,000 exo-planets orbiting other stars. The IAU definition automatically disregards those findings as "planets," yet provides no insight as to exactly what they are to be called. The IAU really made a mess on the definition of planets altogether. The term "planet" should be applicable to every body out there that fulfills the four attributes I listed above. Since our Sun is itself a star, then planets here should not be regarded as special or different from basic planets anywhere in the universe.
Regarding 3) does a planet need to be 'massive' or just spherical? If 'massive' then what minimum size? Obviously the IAU should have said 'star' instead of 'Sun'. I still question our goal in naming something a planet? Are we trying to establish the primary bodies in a solar system? Are we trying to protect the printed textbooks and literature from becoming obsolete? It seems a bit weird when moons are larger than Pluto although they do not obit a star...
Criteria #3, massive enough to maintain a spherical shape, wouldn't require a set size. The mass required would depend on the materials comprising it. Heavier elements, such as metals, would require larger bodies to become & keep sphericality. Icy or stony objects would become spherical at a smaller size. That's why a specific size would not be critical--just the spherical shape. Planets are a very convenient term to categorize star system objects under as a broad type. If you dropped it, you'd have to invent a replacement, which seems like a lot of unnecessary work. The primary difference between planets & moons is determined by what they orbit. Planets orbit stars. Moons orbit planets. Their size is irrelevant.
Planets in our Solar system, that are metals and rock are smaller, while the gas or lighter planets are larger. Seems also that gravity is a key element in creating spherical planets?? And perhaps as in our Solar system the smaller planets obit near their star while the larger planets are farther out...meaning what happened to Pluto?
When a Star forms it is an extremely hot and energetic event. This blasts debris out in an enormous cloud of misc. debris. The new stars radiation prevents water ice from forming for the inner solar system and allows it past a "frost line" and the solar wind also blows lighter elements away, leaving heavier elements to form rocky bodies. The lighter debris forms gas and ice giants further out and gases such as ammonia create Icy bodies beyond that. It is also important to understand that planetary orbits are not static on the cosmic scale and migrate on occasion over Million/Billions of years. Pluto and the rest of the Kuiper belt are pieces not used in planetary formation and mostly ices.
He always gets upset at that. I think he thinks his posts are works of art in and of themselves. No foolin
