Attention Getting Question:
Which planet has the shortest orbit around the sun?
In our solar system, we have two groups of planets and their moons which orbit around the sun in the center. The first group is the four closest to the sun. They our rocky inner planets: Mercury, Venus, Earth and Mars. Then, we have an asteroid belt. The group of outer planets is made up of the gaseous planets: Jupiter, Saturn, Uranus and Neptune. Let’s take a closer look at our inner ones.
Mercury is the closest planet to the sun and has the shortest orbit of only 88 Earth days. It moves at a speed of 48 kilometers a second or 107,372 miles an hour! Mercury turns very slowly on its axis taking 59 Earth days to complete the turn from day to night. It has almost no atmosphere, is rocky with craters, and has no water. Because of its closeness to the sun, the daytime temperature is hot enough to melt lead. It gets up to about 450°C, but it loses all the sun’s heat at night so it plunges to below -180°C. Mercury has no moons. Its distance from the sun is about 58 million kilometers or 36 million miles. Mercury is one of five planets that can be seen without a telescope. It can be seen low in the west just after sunset or in the east just before dawn, if you look closely. It is the smallest of all the planets.
Venus, named for the goddess of beauty, is the second closest planet to the sun. Its surface is rocky with large plains and tall mountains. It has no water. It has a very thick atmosphere of toxic sulfuric acid clouds and a layer of carbon dioxide and nitrogen with a very hot 470°C surface of gases that traps the incoming solar radiation. This creates an intense greenhouse effect. Venus is the brightest planet in our Solar System and is known as the Morning Star and Evening Star. You can even see it in the daylight if you know where to look. Venus orbits around the sun in 225 Earth days, but it takes 243 Earth days for it to rotate once! Venus has no moons and is 108 million kilometers or 67 million miles from the sun. Venus also has phases like our moon, since Venus’s orbit is between the Earth and the sun. You can only see them with a telescope.
The third planet from the sun is our Earth. We know it is the only one where water exists in all three states in nature as water vapor, water, and ice. It also is the only planet with confirmed life existence. Our atmosphere contains largely nitrogen and oxygen with small amounts of many other gases. We have one moon. It takes us 365 ¼ days to orbit around the sun. Earth is 150 million kilometers or 93 million miles from the sun. Earth is the largest of the inner planets.
Mars, the fourth planet from the sun, is named for the Roman god of war. It’s known for its red color from iron oxide. It has a very light atmosphere, polar ice caps of water and carbon dioxide. It has rocky craters, mountains and canyons. Its temperature ranges from 20°C to -123°C. Our space probes that landed on Mars have sent back lots of new information and pictures of Mars. Mars has two moons, Phobos and Deimos. It takes 687 Earth days for Mars to orbit the sun and its day is just a little longer than Earth’s. It is about 228 million kilometers or 142 million miles from the sun. Mars is only one of two planets to be significantly smaller than Earth. If Mars was a softball, Earth would be a basketball.
There is an asteroid belt between Mars and Jupiter since there is a large space between their orbits. Theory has it that it may be that a planet failed to form there due to the enormous gravity of Jupiter. Occasionally, we see a meteor streak across the sky and burn up in our atmosphere, but some have made a crater impact on Earth like in South Africa, northern Arizona, or more recently in Chelyabinsk, Russia. The sizes of meteoroids range from 1 kilometer (or a little over a half a mile) to 940 kilometers (which is around 584 miles) in diameter.
Let’s summarize what we have learned. In our solar system, we have the two groups of planets which orbit around the sun in the center. The first group is the four closest to the sun. They are known as our rocky inner planets. They are Mercury, Venus, Earth and Mars. Earth is the only planet with water found in its three states and confirmed life existence. The outer planets group is next which is made up of the gaseous planets: Jupiter, Saturn, Uranus and Neptune. There is an asteroid belt in between Mars and Jupiter. What have you learned about our inner planets?