I need a definition of a planet and other objects in space that are not planets. This is for granddaughter.?
343980
Well, really, we don't actually have a scientific definition of a planet.  Shocking yes.  Embarrassing even more so.  But we are working on it.  The problem we are facing right now is that we have a large collection of "transition objects" out there, things that sit right on the border of "planet or not."\n\nAt the high mass end, it is pretty clear cut, Things that produce internal energy by fusion are stars, things that don't are planets.  The transition between star and planet thus seems to be at about 12 times the mass of Jupiter.\n\nAt the small end things are muddled because of Pluto.  No good definition of planet exists that keeps only 9 planets.  You can make a definition to include Pluto, but then you must include a lot more objects.  This is where we actually focusing on right now.\n\n"gravitationally round" is thrown around a lot.  My professional opinion is that this one one make the cut.  It seems nice, a planet is a planet because it has enough self-gravity to crush itself into a round shape.  The problem with this definition is that it means we would have about 100 planets in out solar system.  The largest asteroid, Ceres is round, as are most of the icy bodies in the Kuiper Belt.\n\nThe one that seems to be picking up steam is "dynamically dominant."  This basically means that a planet "dominates" the space around them.  Take a look at the area around the earth - nothing else similar to it.  Same with Venus, Jupiter, and the rest. (moons and rings are bound to the planet so they don't count).  Ceres (the largest asteroid) is surrounded by many, many other asteroids.  Same goes for Pluto, it is surrounded by many other icy bodies of similar size (including one that is bigger than it).  This definition leaves us with 8 planets.\n\nReally right now the "planets" are just defined by fiat, they are planets because we call them that and nothing more.  As a planetary scientist I feel a little guilty not being able to actually define one of the words in the name of my field, as such I've honestly been spending far more time working on this whole "planet" mess, than on my own research.
633673
Here are some quick facts:\n\nhttp://www.sir-ray.com/ Enter the site, click astronomy then click on Space Dimensions & Planetary Facts (this site is excellent)\nhttp://www.dustbunny.com/afk/planets/\nhttp://www.kidzone.ws/planets/index.htm\nhttp://nssdc.gsfc.nasa.gov/planetary/planetfact.html\n\nThese sites should be everything that you need~the first site should do it but the other three have little bits of information that might be useful~
1179774
I could think of only two things that may (or may not) be that for which you are searching.\n\nThe first is simply a solar system mobile.  A simple string and crossbar mobile that children can put together.  Unfortunately a slight breeze could have them all going retrograde at once! Moons of the various planets are not generally included and the orbits are not elliptical.\n\nThe second is:\n"An orrery is a mechanical device that illustrates the relative positions and motions of the planets and moons in the solar system in heliocentric model. They are typically driven by a large clockwork mechanism with a globe representing the Sun at the center, and with a planet at the end of each of the arms." *\n\nI watched a program on Leonardo DaVinci and a section of this program had this tucked in the 3rd hour.  Coming back to find your question was interesting to say the least.   I hope this is what you need.
669912
An asteroid is a small, solid object in our Solar System, orbiting the Sun. An asteroid is an example of a minor planet (or planetoid). These minor planets are much less massive than even small planets such as Mercury or Mars. It is believed that most asteroids are remnants of the protoplanetary disc. The incorporation of these remnants into the planets during the formation of the Solar System was prevented by large gravitational perturbations induced by Jupiter. Some asteroids have moons. The vast majority of the asteroids are within the main asteroid belt, with elliptical orbits between those of Mars and Jupiter.
11810
The 10th planet.\nhttp://science.nasa.gov/headlines/y2005/29jul_planetx.htm
599240
Part of the problem is that word "suspended."  It sounds like the planets are "suspended" *from* something, which is not true.  That's why I worry about the mobile idea, with planets "hanging" from coat hangers, as it just reinforces that idea.\n\nThe other thing is that the motion of the planets (their orbit around the sun) is an important ingredient.  They are far enough away that we can't see how fast they are moving.  So they seem to be quite still in the sky (like stars) ... again they *appear* "suspended."  Again, a hanging mobile just reinforces the notion that all the planets are perfectly still.  (BTW, this is why I think every parent should teach a child to find a couple of planets in the sky every few evenings, so the child gets the notion of how it changes position relative to the constellations.  Mars is always really easy to spot, and these days, Saturn is really bright!  That alone can get a child hooked on stargazing, and on science in general!)\n\nHowever, all that said, the mobile idea (styrofoam balls hanging from string) is not a bad one for illustrating the concept of the solar system.  I would just recommend getting it rotating even a little bit to illustrate the idea that the planets are *orbiting* the sun ... they are *moving*.  That is the key lesson I would want a 6-year-old to take away from the project (although what's even more important is that he have fun doing it, and that he asks a lot of questions ... the point really, is to make science fun). \n\nThe actual answer to your "how" question (in case your son really wants to know) is: balanced forces.  The planets have *two* forces acting on them:  (1) the gravity of the sun pulling them inward; and (2) the centrifugal force caused by the speed of their orbit, pushing them out.  These two forces are just balanced enough to keep the planets from falling into the sun, or flying into space.  So if your son were a little older (say 10 or 11) I would try to incorporate elements in the project that represent these two forces.  I have some ideas (and I can present them if you like), but this would be more involved than you probably need to get.\n\nGood luck!
953692
The Planets  \nCompare and contrast the planets in terms of. Size relative to the Earth ... structure may be similar to Earth because of similar density, mass, and diameter. ...www.gpc.edu/~pgore/Earth&Space/GPS/planets.html \nPlanet - Wikipedia  \nBody of considerable mass that orbits a star and that doesn't produce energy through nuclear fusion. Offers an introduction to the planets of our solar system, ...en.wikipedia.org/wiki/Planets \nplanet: Definition and Much More from Answers.com  \n... and other planets occupy a variety of relative ... See also astronomical objects and the solar system's list of objects, sorted by radius or mass. ...www.answers.com/topic/planet
19708
An inner planet is any one of the Solar system's rocky planets that lie inside the asteroid belt: Mercury (planet), Venus (planet), Earth (planet) and Mars (planet). The remaining planets are deemed the outer planets.\n\nThis classification should not be confused with the term inferior planet which designates those planets which lie inside the Earth's orbit (thus Mercury and Venus only).
761176
Earth refers to this planet.  World could mean any planet that is inhabited.  \n\nSince we don't know of any other inhabited planets, the two are pretty much interchangeable outside of science fiction.
877159
I have been doing a presentation on Pluto is not a planet.\n\nI put up a bulletin board with the pictures of the planets with special pages showing Ceres, Pluto, and Eris.
942204
We have 8 'planets' (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune).  We have several more 'dwarf planets.'  \n\nThe difference is that, during planet formation, a planet's gravity will pull in all the material around it, leaving a planet surrounded \nby empty space.  This is referred to as 'clearing the neighborhood.'  A dwarf planet's gravity is not sufficient to pull in all the material around it, so it does not clear its neighborhood.  \n\nPluto is now a dwarf planet, along with several asteroids and other celestial bodies.  In fact, Pluto is a binary planet, because it and it's moon, Charon, orbit each other (the center of Charon's orbit is not a point inside of Pluto, but rather a point between the two bodies).  So Pluto probably won't even be considered a dwarf planet for long.\n\nThis Xena, as you call it, is twice the size of Pluto.  That's what reignited this whole controversy.  It's real name is 2003UB313.  Xena was only given to it as a temporary name.
70556
Planet is a difficult word to use to describe objects in the outer solar system.  They are typically called trans-Neptunian objects, Kuiper Belt objects, or inner Oort cloud objects since they are very much unlike the four inner and four Jovian planets.  \n\nHowever that said an object by the name of Xena was found recently.  Based upon its distance and reflected light astronomers believe it is larger than Pluto.  Its orbit puts it near the same distance as Pluto's orbit...slightly further.  Also Sedna was discovered also recently.  Called an inner Oort cloud member it is slighly smaller than Pluto and it appears to have peculiar properties like being overly red in color.\n\nAnd of course there are roughly 150 extra-solar planets discovered around other stars.
572044
Yes UB313 (which was not discovered last year, but in 2003).\n\nBe careful calling it a planet, however.  Web sites and journalists love to talk about the "tenth planet" because it sounds more exciting that "yet another trans-neptunian object (TNO)."  However, astronomers (the International Astronomical Union, or IAU) do not officially recognize this as a "planet."  This may change later this year (in September) when the IAU is scheduled to come up with a more solid definition of what a "planet" is (how big, what orbit, etc.) ... but until then, you sound more like a real astronomer if you don't call it a "planet."
570740
Any of numerous small celestial bodies that revolve around the sun, with orbits lying chiefly between Mars and Jupiter and characteristic diameters between a few and several hundred kilometers. Also called minor planet , planetoid .
808438
The science writer, Dava Sobel, has just published a nice little book that talks about all this stuff for non-science people. Check it out at the library. It's called "The Planets" and it has the latest stuff in it.
1041594
Things that are orbiting our planet are in a state of constant "free fall". That is why they appear to be weightless. The force of gravity is still very high on the astronaut.
331575
The earth travels through space.\nIt supports life.\n\nYou could call it a space ship. Yes.\n\nWelcome aboard Space Ship Earth