Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune are the eight planets. Mercury is the nearest planet to the Sun. Neptune is the farthest away. The other seven planets can be seen with the naked eye.
Mercury is a terrestrial planet, meaning that it is mostly made up of rock and metal. It has no atmosphere or water and is therefore considered a void of space. The only place on Mercury where you might find ice is at the bottom of craters deep within shadowed regions. However, most of the surface is exposed to direct sunlight all the time, so it must be either very hot or very cold. Scientists think that parts of it may be as cold as -400 degrees F, but more likely it's just too hot for anything living.
Venus is another terrestrial planet. It has over 90% clouds and cloud cover almost everywhere you look. Although you could walk from one end to the other in just under an hour, there is nothing useful anywhere on the surface. Most scientists believe that there is ice underneath the clouds, but it's probably not enough to support life.
Earth is the only planet that is able to support life as we know it. It has an iron core, liquid metallic hydrogen shell, and a weak magnetic field. The planet orbits the sun every 365.
The solar system has eight planets. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune are the planets nearest to the Sun and furthest away. Terrestrial planets are the first four planets discovered. They are primarily solid and built of rock and metal. The other four are gas planets - they consist mainly of hydrogen and helium with some traces of other elements.
The term planet comes from the Greek word for wanderer, because astronomers used to think that these bodies moved across the sky in circles that were not exactly the same size or distance apart. But now we know that all the planets except Pluto move in ellipses whose long axes are not perpendicular to the plane of the Solar System but lie at any angle between 30 and 60 degrees to it. And even Pluto's orbit is not exactly circular; it changes length over time due to gravitational interactions with the other objects in the Solar System.
Our knowledge about these objects has increased greatly since they were first discovered. It is now known that there are other worlds outside our own solar system that share many properties with the ones here on earth. These other planets include mars, jupiter, saturn, uranus, neptune, and pluto. The number of planets in the galaxy may be much higher than this, however. Astronomers believe that there could be as many as 100 billion planets in the Milky Way alone!
The Planets' Size and Order Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and ultimately Neptune are listed in order of proximity to the Sun. Jupiter is the biggest planet in the solar system. It is followed by Saturn, Uranus, Neptune, Earth, Venus, and Mars, with Mercury being the smallest. The rest of the universe consists of many other stars and galaxies.
The sizes of the planets are estimated based on their distances from the Sun. Thus, the larger a planet is, the further it is from the Sun.
However, the actual size of a planet is not as important as its mass. Mass is a measure of how much matter a body contains; the greater its mass, the more matter it contains. Mass is one way to quantify gravity. The stronger the gravitational force between two objects, the closer they will be together. So, the heavier a planet is, the stronger its gravity will be.
In addition, gravity also depends on distance. The closer an object is to another object, the more its weight affects it. So, if we look at the Earth and Moon, then the Moon tends to follow or "orbit" around the Earth. This is because the Moon is too small to leave the Earth's gravity behind it. However, if we zoom out into space, then we can see that the Moon appears to orbit around something else: the Earth!