Home, Sweet Home. The Solar System

Overview Our solar system is comprised of 8 planets orbiting a massive G2V yellow star. Stars are classified by the following ditty – “Oh, Be A Fine Girl. Kiss Me.” Our Sun is considered a dwarf star, even though it has a diameter of 1,392,000 km (approximately 109 times that of earth). Our sun exerts a gravitational force which keeps a planet (Neptune) in orbit over 4.5 billion kilometers away.

The Sun Our Sun is a nuclear fusion reactor – converting hydrogen into helium. This fusion reaction fuses approximately 630 million tons each second. The Sun has been burning like this for (arguably) 4.5 billion years and is estimated to be about half way through its lifespan. At that point, the Sun will expand into a Red Dwarf and envelop Mercury, Venus, and Earth.

Organization You can remember the eight planets by the statement “My Very Energetic Mother Just Sent Us Nothing”. Pluto, which was discovered in 1930 and was demoted to dwarf planet in 2006. The first 4 planets from the Sun are considered Terrestrial, and the remaining 4 are considered Jovian. The main difference between Terrestrial and Jovian planets is their size.

Organization

Mercury Named for the Roman god of messengers. Mercury is the closest planet to the Sun. Mercury orbits the Sun once every 88 Earth days. The surface of Mercury is pockmarked with craters from collisions with asteroids and comets and resembles our Moon. Mercury has an atmosphere comprised mainly of hydrogen and helium. Temperatures on Mercury vary from -280oF to 800oF. The gravity on Mercury is nearly 1/3 of that of Earth.

Venus Named for the Roman goddess of Love and Beauty. Venus orbits the Sun every 225 Earth days. The surface of Venus is rough and home to many craters and volcanoes. Venus has an atmosphere comprised mainly of CO2 with clouds of sulfuric acid. The temperature on Venus does not vary from 460oF and the atmospheric pressure is 100 times that of Earth. The gravity of Venus is about 90% that of Earth. Venus is considered to be somewhat of a twin to Earth.

Earth Earth is the densest and fifth-largest of the 8 planets. Based on its distance from the Sun, Earth is the only planet to possess water in all 3 states of matter. Our atmosphere provides a temperature range hospitable to life. As a result, the only life found in our solar system resides on Earth. All life that has arisen on Earth, has remained on Earth. This includes minimal space travel. 517 humans have been in space, with a scant 12 having set foot on the Moon.

The Moon Earth’s Moon is a satellite trapped in a elliptical orbit. The Moon is in a synchronous rotation to Earth, always presenting the same surface. Even though the Moon appears bright, it has a dark surface and possesses the same reflectivity as coal. 12 humans have walked on the Moon between 1969 and 1972. It has been long thought that the Moon was formed after a huge asteroid collided with the Earth, but this theory has recently been disputed. The Moon possesses a gravity about 1/6 that of Earth.

Mars Named for the Roman god of War. Mars is approximately half the diameter and has 11% of the mass of Earth. Early astronomers noted surface features on Mars that led them to believe they were seeing canals of liquid water. Water is found on Mars in the polar ice caps. The atmosphere of Mars is 95% CO2, with trace amounts of oxygen gas. Temperatures on Mars vary between -125oF and 23oF. The gravity on Mars is about 1/3 that of Earth. The period of Mars is 687 Earth days. Rovers and landers have been placed on Mars. Assuming you could launch with sufficient fuel, a trip to Mars would take slightly more than 6 months in each direction.

Jupiter Jupiter is more than 2.5 more massive than all the other planets combined. Jupiter is composed primarily of hydrogen and helium, with a possible rocky core. Jupiter has more than 1,321 times more volume than Earth, but is only 318 more massive. Jupiter possesses a massive storm, named the Great Red Spot, which was first noted in the 17th century. Jupiter’s surface temperature is believed to hover around -229oF. The gravity on Jupiter has been estimated to be about 25 m/s2. Since Galileo first discovered 4 Jovian moons, more than 60 additional moons have been identified.

Comet Shoemaker-Levy 9 In 1993, a comet trapped in orbit around Jupiter was discovered. As astronomers studied this comet, they noted that it was spiraling in to the planet. The comet broke into pieces due to the gravity of Jupiter. Over 6 days in July of 1994, pieces of this comet slammed into Jupiter. The largest fragment (G) caused an explosion equivalent to 6,000,000 tons of TNT. The resulting fireball was measured as raising the temperature from 130K to 24,000K.

Saturn Named after the Roman God of Agriculture, as it appeared prominently in the sky around harvest time. Saturn has a mass 95 times that of earth, but possesses a density 1/8 that of Earth. Saturn orbits the Sun approximately every 10,000 days. With an atmosphere comprised mainly of hydrogen and a rocky core containing iron, nickel, and rock, Saturn is the second largest planet and a gaseous giant. The temperature on saturn varies from -418oF at the cloud top to 21,092oF in the layer of metallic hydrogen. Saturn’s gravitational field is slightly stronger than that of Earth (10.44 m/s2). The most notable feature of Saturn would be its rings, which surround the planet and extend to 75,000 miles from the cloud top.

Uranus Named for the Greek God of the Sky. Located approximately 20x the distance from the Sun as that of Earth, Uranus has a period of 84 years and gets 1/400 the amount of sunlight as Earth. Uranus has an atmosphere of hydrogen and helium surrounding a rocky core. Uranus is the coldest planet in the solar system, with an average temperature of -371oF. Tilted almost 90o, Uranus spins along the plane of orbit with the Sun. Uranus is an icy orb that bears a striking similarity to its neighbor – Neptune.

Neptune Named for the Roman God of the Sea. Neptune is similar to Uranus in size and composition. The period of Neptune is approximately 165 years. The average temperature is -328oF. With the demotion of Pluto to a dwarf planet, Neptune is the outermost planet in our solar system.