Planets | Sun Earth and other planets
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Solar System Planets

 Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto


    Mercury is the smallest and fastest planet in the solar system. It is also the closest planet to the sun. It has no moons. Mercury is the smallest of the eight planets in our solar system. It is only a little bigger than Earth's moon. It would take more than 18 Mercurys to be as big as Earth.


    Venus is the second planet from the sun and our closest planetary neighbor. Similar in structure and size to Earth, Venus spins slowly in the opposite direction most planets do. Its thick atmosphere traps heat in a runaway greenhouse effect, making it the hottest planet in our solar system with surface temperatures hot enough to melt lead. Glimpses below the clouds reveal volcanoes and deformed mountains.


    Earth is the third planet from the sun and the fifth largest in the solar system. Just slightly larger than nearby Venus, Earth is the biggest of the terrestrial planets. Our home planet is the only planet in our solar system known to harbor living things. The name Earth is at least 1,000 years old. All of the planets, except for Earth, were named after Greek and Roman gods and goddesses. However, the name Earth is an English/German word, which simply means the ground.

  • MARS

    Mars is a cold desert world. It is half the diameter of Earth and has the same amount of dry land. Like Earth, Mars has seasons, polar ice caps, volcanoes, canyons and weather, but its atmosphere is too thin for liquid water to exist for long on the surface. There are signs of ancient floods on Mars, but evidence for water now exists mainly in icy soil and thin clouds.


    Jupiter is the fifth planet from our sun and the largest planet in the solar system. Jupiter's stripes and swirls are cold, windy clouds of ammonia and water. The atmosphere is mostly hydrogen and helium, and its iconic Great Red Spot is a giant storm bigger than Earth that has raged for hundreds of years.


    The second largest planet in our solar system, adorned with thousands of beautiful ringlets, Saturn is unique among the planets. It is not the only planet to have rings -- made of chunks of ice and rock -- but none are as spectacular or as complicated as Saturn's. Like fellow gas giant Jupiter, Saturn is a massive ball of mostly hydrogen and helium.


    The seventh planet from the sun with the third largest diameter in our solar system, Uranus is very cold and windy. The ice giant is surrounded by 13 faint rings and 27 small moons as it rotates at a nearly 90-degree angle from the plane of its orbit.


    Dark, cold and whipped by supersonic winds, Neptune is the last of the hydrogen and helium gas giants in our solar system. More than 30 times as far from the sun as Earth, the planet takes almost 165 Earth years to orbit our sun.


    Discovered in 1930, Pluto was long considered our solar system's ninth planet. But after the discovery of similar intriguing worlds deeper in the distant Kuiper Belt, icy Pluto was reclassified as a dwarf planet.

Geocentric Solar System Model

In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system) is a superseded description of the universe with Earth at the center. Under the geocentric model, the Sun, Moon, stars, and planets all circled Earth.

Where is the solar system in the galaxy?

It’s between the Sagittarius and Perseus Arms of the Milky Way. The image below shows it. Our sun is located the Orion Arm, or Orion Spur, of the Milky Way galaxy. It’s a minor spiral arm, located between two other arms.

Play the video which explains retrograde motion of planets.

How Do We Know the Earth Orbits the Sun?

This photo is of the Geocentric system of the Solar System where the Planets and Sun orbit the Earth.

If you looked at the location of Mars each night, it might sometimes do this.

How does the geocentric model deal with this new evidence? Here are some of the highlights.

Ptolemy develops a geocentric model that has the planets moving around the Earth. However, in order to account for retrograde motion, he put the planets on circles that move in circles.
Copernicus suggests a heliocentric model. His model has the planets moving around the Sun in circular orbits. This can explain retrograde motion, but his model doesn't fit all the planetary position data that well. Really, it's no better than Ptolemy's geocentric model.
Kepler proposes that the planets do not orbit in circles. Instead, they have elliptical orbits. This agrees with the observational data very well.
Newton develops a model for gravity that also says planets would have elliptical orbits.
Galileo gets a telescope and looks at the sky. He see stuff that suggests the Earth orbits the Sun.