The number of galaxies in the universe is largely unknown to humans, in fact, scientists speculate that there might be an infinite number of galaxies. Our galaxy, the Milky way, is estimated to host about 100 billion planets most of which orbit a star. In the near past, astronomers have discovered hundreds of planets in our galaxy, some of which exhibit the characteristics of planet Earth raising the speculation that they might support life. Our solar system comprises of the sun, eight planets and their moons, and several small solar system bodies. For a long time, the sun’s solar system consisted of nine planets until Pluto was downgraded from being a planet for failing to meet criteria that a planet must clear its orbit and have no “neighbor” that is larger or equal its mass around it. It was discovered that Pluto is part of a group of six space objects that orbit the Kuiper Belt and is not the largest of the six.
Mercury is the closest planet to the sun; it is also the smallest of the eight planets. Mercury completes a full revolution around the sun in 88 days. It is a rocky planet with an equatorial radius of 1,516 miles and has a density of 5.427 g/cm3 making it the second densest planet in the solar system. Mercury does not have an atmosphere meaning then temperature fluctuates from 840 degrees Fahrenheit during the day to minus 275 F during the night. Its orbit is oval shaped and is one of the planets that can be viewed from the Earth.
Venus is the second-closest planet to the sun. It covers a revolution within 224.7 days and a rotation period of 243 days; the longest of any planet in the solar system. Venus is the hottest planet with a mean temperature of 863 °F because its atmosphere is dense and traps warm air. It appears bright in the morning and in the evening which makes it visible in certain areas of the Earth. It is the closest planet to the Earth, making it the first planet to be visited by an earthly object (Mariner 2) in 1962.The dense hot atmosphere has rendered the planet inaccessible to man.
Planet Earth is home to humans and is the only planet known to host life. It completes a revolution around the sun in 365.256 days traveling a distance of 584 million mi. It is 92,955,820 miles away from the sun and is the third planet from the sun; it is estimated that its formation began 4.54 billion years ago. Its total surface area is 196,940,000 sqm; 71% of which is covered by water while the remaining 29% by land. The Earth’s atmosphere protects life from the uninhabitable space, shields us from harmful radiation, and controls the weather. It is the densest planet in the solar system.
Mars, also known as the “red planet,” is the fourth planet in our solar system and the second smallest. It has a solid surface just like the Earth, but its atmosphere is thin. Mars is half the size of the Earth and is 143,000,000 miles from the sun; it also completes a revolution around the sun in 779.96 days. It is visible from the earth in the evening due to its bright surface. Liquid water is not found on the surface of the planet due to the low atmospheric pressure. Researchers are examining the possibility that life once existed on Mars. Scientists believe that the ice caps on the poles of the planet is water and that the ice on the south pole would fill the planet's surface to a depth of 36 ft if melted.
Jupiter is the fifth and largest planet in the solar
system. Its mass is 2.5 times the total
mass of the other planets combined. Jupiter is a gaseous planet meaning that it
has no solid surface although researchers believe that its core is solid. It is
89,000 miles wide at the equator and large enough that all the planets or 1,300
earths would fit inside it. It is primarily made of hydrogen and helium.
Jupiter’s atmosphere is violent, wind speed travels at an average speed of 340
mph, twice the speed of a category five hurricane on earth. The planet has
three rings made of dust particles and are difficult to see. It takes 12 Earth
years to make a revolution round the sun.
Saturn is the second largest planet after Jupiter. It is a gaseous planet just like Jupiter but with nine continuous rings and several ringlets made or rocks and ice. It is considered the most beautiful planet in the solar system and is composed of hydrogen and helium. Its diameter is nine times that of the Earth. Its volume equals that of 763.5 Earth(s), and its surface is equal to 83 Earth(s). However, it weighs only one-eighth the mass of the Earth. Saturn has nearly 150 moons, 53 of them have been named, 62 of them have been identified as having orbits while the rest are moonlets in the rings.
Uranus is the seventh planet and the third largest in the solar system. Its surface is composed of a frozen component and is therefore considered an ice giant. However, its atmosphere is made up of hydrogen and helium alongside other “ices” such methane, ammonia, and water. Although it is not the furthest planet from the sun, it is the coldest with temperatures that reach −224 °C because it is the only planet that does not radiate heat from its core. It is 2 billion miles from the sun.
Neptune is the furthest planet from the sun. It was first considered a fixed star by Galileo who used mathematical predictions to discover it rather than the regular method of making observations. It is Nearly 2.8 billion miles from the sun and completes a revolution round the sun in 164.8 years. Neptune completed its first revolution in 2011 since it was discovered in 1846. It has 14 known moons with Triton being the largest. It atmosphere consists of hydrogen and helium. It is the windiest planet in the solar system, nine times the average wind speed of the Earth. Recently, NASA discovered that Neptune had flowing rivers and lake of liquid methane.