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Arthur T Knackerbracket has found the following story:
It turns out that Earth is not a planet. Asteroid 2016 H03, first spotted on April 27, 2016, by the Pan-STARRS 1 asteroid survey telescope on Haleakala, Hawaii, is a companion of Earth, too distant to be considered a true satellite.
"Since 2016 HO3 loops around our planet, but never ventures very far away as we both go around the sun, we refer to it as a quasi-satellite of Earth," said Paul Chodas, manager of NASA's Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California.
Asteroid 2016 H03 is proof that Earth has not cleared the neighborhood around its orbit. Therefore, under the definition of a planet vigorously defended by the IAU [International Astronomical Union] since the adoption of Resolution 5A on August 24, 2006, Earth is a 'dwarf planet' because it has not cleared its orbit, which is the only criteria of their definition that Pluto fails. (I think we'll eventually discover that very few of the 'planets' have cleared their orbits).
Most of us who were baffled by the IAUs declaration and outraged at the obvious discrimination of Pluto knew there was something wrong, even if we couldn't put our finger on it — we just 'knew' Pluto was a planet, right?
[...] Here's what all of us non-scientists intuitively understood all along: "A planet is defined as an astronomical body that "has not undergone nuclear fusion, and having sufficient self-gravitation to assume a spheroidal shape" — in other words, it's round and not on fire.
How could the distinguished scientists be so wrong?
-- submitted from IRC
(Score: 4, Insightful) by number6x on Monday April 03 2017, @09:00PM (10 children)
This is not what is meant by 'cleared the neighborhood around its orbit'. If it was, planets would not be allowed to have moons.
Asteroid 2016 H03 is completely dominated by Earth's gravity. If the Earth wasn't there Asteroid 2016 H03 would be circling the sun at its own pace. In essence, Asteroid 2016 H03 orbits Earth's orbit, and its path is controlled and determined by the effects that Earth's gravity has on it. This makes it similar to asteroids in Earth's trojan points.
A better (but completely silly) argument would be that Earth, and all the other planets, have not 'cleared' their orbits because, occasionally, a comet comes in and crosses their orbits, thus 'proving' that their orbit is not cleared. It would be a very pedantic interpretation of the definition.
Just quit getting so hung up about the definition of a planet, because it is kind of arbitrary and will change depending on the group of researchers needs. Labeling and classifying things belongs to the type of science often referred to as 'butterfly collecting'. The task of labeling things and sticking them in the correct pigeon holes.
Butterfly collecting is sometimes useful. Listing chemicals by their properties led to the periodic chart. The property categories were later explained when the make up of atoms as a positively charged nucleus surrounded by 'shells' of electrons. atoms that had full shells acted in a certain way. atoms that were a few electrons short acted in their way, and atoms that had a few electrons in their next shell acted in their way. Each of these groups formed columns in the periodic table. The explanation of why the atoms exhibited their groups of behavior came long after the behavior was recorded in the periodic table.
Butterfly collecting the various groups of animals leading to Kingdom, Phyla, Class, Order, Family, Genus, and Species led to understanding of evolution and the observation how traits were passed down across generations. Some of these labels had to be re-adjusted after genetic testing was developed. Not every animal that looked alike was as closely related as thought, and some closely related animals looked different from each other. However, the 'butterfly collecting' approach was a really good first approximation.
Defining the groups of objects in the solar system is done to help us gain new insight into commonalities and differences. It is like applying a filter. You can apply this filter now, and another filter later, re-aligning the definitions.
That is what this is about, made up labels and definitions. I don't mean to imply that they are just random and arbitrary. They are meaningful and helpful. They are not just arbitrary. However, another set of meaningful and helpful definitions and labels may be useful for other purposes and lead to different insights.
(Score: 3, Informative) by hendrikboom on Tuesday April 04 2017, @12:50AM
Labeling and classifying things belongs to the type of science often referred to as 'butterfly collecting'.
Labeling and classifying things belongs to the type of science often referred to as 'taxonomy'.
(Score: 2) by bzipitidoo on Tuesday April 04 2017, @04:30AM (7 children)
Oh come on, the article was flamebait. You're right, this asteroid does not demote Earth's status from planet to dwarf planet.
The article points up a problem. A comet crossing a planetary orbit does not change the status of a planet. Yet, planetary status does depend on external factors. Should it? I would say it should depend on external factors as little as possible. Move Pluto further out so that not only does it not cross Neptune's orbit, it is not in any resonance at all with Neptune, and what happens? Suddenly Pluto qualifies as a planet because its neighborhood is clear? That's the basic problem with the definition.
Move Earth into orbit around Jupiter, and suddenly Earth is no longer a planet, it is only a moon. Planets orbit stars or nothing. An object that orbits a planet is a moon. And that's okay. It's a useful distinction.
What about a round body too small to fuse elements in interstellar space, orbiting the galactic center rather than any star? Is that a planet? Sure it is! If Mercury gets ejected from the solar system it would not suddenly lose its status as a planet.
(Score: 0) by Anonymous Coward on Tuesday April 04 2017, @05:30AM
https://en.wikipedia.org/wiki/Rogue_planet [wikipedia.org]
(Score: 2) by dry on Tuesday April 04 2017, @05:39AM (5 children)
Isn't one of the definitions of a planet that it orbits the Sun? Currently there are exactly 8 planets in the universe and if Mercury was ejected, it would no longer be a planet.
(Score: 2) by bzipitidoo on Tuesday April 04 2017, @06:21AM (3 children)
If you want to be extremely pedantic, there are only 5 planets: Mercury, Venus, Mars, Jupiter, and Saturn. The ancients could not see Uranus or Neptune, and did not realize that what they were on, the Earth, belonged in the same category as the 5 wanderers.
I do not see any useful distinction between planet and exo-planet. They all orbit suns, or are rogue planets. We've found thousands of exo-planets.
Can a planet orbit a black hole, and still be considered a planet? Why not?
(Score: 2) by maxwell demon on Tuesday April 04 2017, @07:12AM (2 children)
No. They orbit stars. There are many stars, but only one of them is called sun, just like there are many planets, but only one is called earth.
It's bad enough that the term "moon", which used to be a name just for the earth moon, now has double use as both a specific body and a class of bodies. No need to add more ambiguities like that, when we already have a word for the class. What's wrong with "star"?
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by bzipitidoo on Tuesday April 04 2017, @12:59PM (1 child)
"sun" means the star or stars within the same solar system as the planet referred to. Sol is our sun.
Here is a pic of SUNset on Tatooine: https://en.wikipedia.org/wiki/Tatooine#/media/File:SW_binary_sunset.png [wikipedia.org]
"moon" is not a problem. Can call ours Luna, if "the Moon" (with capital 'M') doesn't suit.
(Score: 2) by dry on Wednesday April 05 2017, @03:56AM
Too lazy to load your link, but I didn't realize that Tatooine was close enough that the Sun was noticeable.
Just like we can talk about Sirius rise or setting (very important to the ancient Egyptians), Aliens around Sirius could talk about the Sun setting as the Sun would be one of the brighter stars in the sky.
I talk English, not Latin, and call the Sun the Sun and the Moon the Moon.
(Score: 2) by Scruffy Beard 2 on Tuesday April 04 2017, @06:25AM
Nice catch. It looks like exoplanets are merely undefined by the IAU though:
Definition of a Planet in the Solar System [iau.org]
I also now know why the press-release incorrectly classifies Earth as a planet: it was an error in the footnote of the resolution!
(Score: 1) by All Your Lawn Are Belong To Us on Tuesday April 04 2017, @05:06PM
Well said! My personal view is that we who are amateur astronomers (and professional astronomers) should have other fish to fry and things to be concerned with than reopen the, "Pluto is a planet," argument again. But I'm comfy *either* way.
At least I do. Someone else's mileage may vary.
This sig for rent.