What is the difference between a planetary object and a moon

This changed when Galileo discovered four large objects orbiting Jupiter. This makes people think the technical definition of moon is a satellite of another object, and so we call lots of objects that orbit Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, Eris, Makemake, Ida and a large number of other asteroids moons.

When you start to look at the variety of moons, some, like Ganymede and Titan, are larger than Mercury. Some are similar in size to the object they orbit. Some are small and irregularly shaped, and some have odd orbits. If we try to fix the definition for what is a moon and how that differs from a planet and asteroid, we are likely going to have to reconsider the classification of some of these objects, too.

You can argue that Titan has more properties in common with the planets than Pluto does, for example. The most recent naming challenge astronomers face arose when they discovering planets far from our Solar System orbiting around distant stars.

These objects have been called extrasolar planets, exosolar planets or exoplanets. Astronomers are currently searching for exomoons orbiting exoplanets. Ideas for how planets form also suggest that there are planetary objects that have been flung out of orbit from their parent star. One of the easiest ways to tell is the way that the light twinkles.

The planets in our solar system are a lot closer to Earth than the stars are, meaning that the light that they give is brighter than stars, although planets do not emit their own light. The sun is a point of light for all of the planets in our solar system, therefore the light that we see from the other planets in our solar system is a reflection of the light from our sun being reflected from that planet.

In Ancient Astronomy, in order to distinguish whether or they were looking at a planet or a star, astronomers would study the movement of that specific source of light over the course of a few nights. Planets, like the sun and the full moon, rise and set and follow a celestial path across the night sky.

While stars do move, they move in a differently in comparison to the planets in our solar system. Stars move in a circular pattern around the North Star, therefore, if the light that you see appears to move in a straight line over the course of a few nights, it is most likely a planet!

If you have figured out the difference between the stars and planets in the night sky, how can you tell which planet that you are looking at? One way to tell the difference is by observing the colour of the planet. Not all the planets in our solar system have a specific colour, however the most prominent planets in the night sky can appear to have some sort of colouration. It is recommended to use a telescope on a clear night if you are trying to distinguish the colour difference between the planets in the night sky.

Lucky are those whom job it is to get up every morning and go to work looking at the moon. Very cool. I had no idea the moon was so much like Earth. I can buy the idea that the Moon has some of the same properties that some planets do, but a cat having four legs and a tail does not make it a dog.

If Earth were an 8-foot ball, its moon would only be a 2-foot ball. If I were to describe a true binary planetary system, it would be Pluto and its companion Charon. In short, I think there will be many moons in the solar system — especially around Jupiter and Saturn, which resemble Earth more than the planets they orbit.

But as simple as it is, we should define planets as primary objects in orbit of a star once it is proven they are not comets or asteroids. Decades ago a spiritual master in India said that our Moon is a cooled down planet, specifically, a cooled down Earth … that it had been like our Earth.

I have always wondered what a study would reveal looking at the Moon from this perspective. Looks like I am about to find out. I have a few thoughts on your post:.

What about TLPs in addition to Moonquakes? Hi, To suggest the Moon and Earth are alike is complete rubbish. One of the latest theories, is that the Earth and a Mars sized planet collided early in the formation of the Solar System, and the remains coalesced to form the Moon. This aside, the Moon has never had an atmosphere or life, and never will.

It also moves away from Earth at approx. Then maybe, when it orbits the Sun on its own, we can call it a dwarf planet? We wont be around to see it though…………. Hi Rick, There is no way for us to know if the Moon never had an atmosphere or life millions of years ago, though I agree, it probably never will in the future. And theories are just guesses, not necessarily correct and not proof of anything. Or perhaps Eris and all the other newly discovered round worlds should be considered planets?

We could classify the worlds of the solar system in many different ways: by size mass or diameter , composition metal, rocky, icy, gassy, or combinations thereof , location orbiting near or far from the Sun, alone or circling another world , whether or not it has an atmosphere, magnetic field, oceans, weather, present-day geologic activity, and more.

What combination of qualities makes something a planet? If a scientist is interested in impact craters or subsurface oceans, does it matter if a world orbits the Sun or another planet? The International Astronomical Union IAU is an international organization with more than 10, members that fosters collaboration among astronomers. Following the discovery of Eris in , the IAU attempted to clear up the confusion surrounding planethood by voting on a new definition for planets at its General Assembly in At the end of the General Assembly, a majority of the remaining members still present for the vote passed the IAU planet definition resolution.

The resolution said that a planet must:. The first 2 criteria orbit the Sun and be round are easy to understand, but the third has caused confusion. Another way to put this is: a planet is a world that has dramatically more mass than anything else that orbits near it.

According to this astronomical definition, Neptune is a planet and these other worlds are not planets though they may be dwarf planets.

Others pointed out some complications of applying it. Not only astronomers study planets, of course. Now that spacecraft routinely explore our solar system, other kinds of scientists can study planets, too. Geoscientists care about the intrinsic properties of a world like its surface landforms, mass distribution, and composition more than the location of the world.

Mass is the most useful predictor of the kinds of physical processes that can happen on a world, regardless of where it is in the solar system. Composition, location, and history are also important, but you can predict a lot about a world if you only know its mass. Stars are objects that are or used to be capable of nuclear fusion.

Planets are too small ever to have fused atoms. But what is the boundary between planets and not-planets at the small end of the size range? To figure out where that boundary lies, and how geoscientists might classify planets , it helps to know what planetary scientists have learned about the variety of worlds in our solar system, and which ones experience planetary processes like volcanism, tectonics, and weather. They are often loosely-assembled piles of rubble with large, empty void spaces between their component blocks.

They are not considered to be planets by anyone.