Ceres was considered a planet in the first half of the 1800’s, along with a bunch of things in the asteroid belt. There was a point where there were 64 planets.
In the present state of knowledge astronomers give us the following list:
Sixty-four “primary planets” revolving round the Sun as our Earth does.
Twenty satellites, including our Moon.
Of the sixty-four primary planets fifty-six are asteroids, comparatively small bodies, all of which were discovered in this century, and fifty-two since the year 1844.]
The phrase refers to an orbiting body (a planet or protoplanet) “sweeping out” its orbital region over time, by gravitationally interacting with smaller bodies nearby. Over many orbital cycles, a large body will tend to cause small bodies either to accrete with it, or to be disturbed to another orbit, or to be captured either as a satellite or into a resonant orbit. As a consequence it does not then share its orbital region with other bodies of significant size, except for its own satellites, or other bodies governed by its own gravitational influence. This latter restriction excludes objects whose orbits may cross but that will never collide with each other due to orbital resonance, such as Jupiter and its trojans, Earth and 3753 Cruithne, or Neptune and the plutinos.[3] As to the extent of orbit clearing required, Jean-Luc Margot emphasises “a planet can never completely clear its orbital zone, because gravitational and radiative forces continually perturb the orbits of asteroids and comets into planet-crossing orbits” and states that the IAU did not intend the impossible standard of impeccable orbit clearing.[2]
Trojans and Greeks orbit Jupiter’s LaGrange points in a stable orbit and so they are governed by Jupiter’s gravity. You could say they’re really weird moons orbiting semi-stable points Jupiter creates.
Arenyou gonna start calling Ceres, Haumea, Makemake, and Orcus planets?
We went through this 150 years ago ehen the asteroid belt was discovered. Every astronomer wanted credit for discovering a new planet, so at one point there were 15 before all the astronomers got together and said it was untenable.
They found more evidence for its existence recently, but no. Nobody has ever seen it or even found out in which direction to look. The evidence is that the other planets move in ways that only makes sense if there is some mass somewhere pulling their orbits.
Sort of like having to discover the moon from watching the tides in the sea.
this method is how we discovered Neptune and Pluto and many exoplanets. Kepler’s laws are extremely specific about orbits, so once you pin down the disturbances the planet makes you significantly narrow down the places it can be.
Yes, the difference being that the existence of Neptune and Pluto could be visually confirmed through telescope more easily. They’re also not visible to the naked eye, but they can be found in telescopic images by comparing to a map of the sky at other times. Later on they were visited by probes.
I don’t know what counts as a discovery of a planet. Personally, I’d like to see any kind of real data from the planet before claiming it discovered.
The calculations can be 100% correct, but they’re not verified until there’s some kind of external proof.
The planet X (or 9 or whatever) has yet to be seen in any kind of way.
So far the calculations have been confirmed by other calculations showing the same thing, and they’re most certainly correct, but the “solid” proof is still missing.
(It doesn’t have to be solid or visual, I don’t know the English word for it; it just needs to originate from the actual existence of the planet and not only from the effects of its theoretical existence.)
You know, this post made me realize something. Some people are viewing it in terms of “rank”, instead of an arbitrary scientific classification designed to efficiently communicate ideas in a clear and concise way.
It’s like … mythology or something, and the planet(oid) being anthropomorphized.
Do people also view kingdom, phylum, class, order, family, genus, species as “ranks” of some sort, with some intrinsically greater value being given to some over others?
Do people also view kingdom, phylum, class, order, family, genus, species as “ranks” of some sort, with some intrinsically greater value being given to some over others?
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