Top 10 Facts About The Solar System

1: Solar System is 4.6 Billion Years Old

The solar system is 4.6 billion years old and 99.86% of its mass is contained in our Sun, a rotating yellow dwarf star whose powerful gravity causes numerous objects to revolve  around it in nearly circular orbits including the planets, moons, comets, asteroids, meteoroids, dust and gas.

2: Sunlight Takes Around 8 Minutes To Reach Earth

The Earth is located 93 million miles (150 million kms) away from the Sun, a distance known to astronomers as an astronomical units or AU. Traveling at the speed of light (186,282 miles per second), sunlight is able to cross this vast distance in around 8 minutes 20 seconds.

3: Solar System 2 Light-years Across

The size of a solar system is determined by how far its sun’s gravity overpowers other objects in the region, which in the case of the Sun extends to the Oort Cloud, a reservoir of cometary material located between 5,000 and 50,000 AU away. That boundary would give the solar system a diameter of around 2 light-years across.

4: Planets Are Made of Rock or Gas

The 8 planets in our solar system are divided into the inner planets of Mercury, Venus, Earth and Mars, which are basically made of rock and metal; and the outer planets of Jupiter, Saturn, Uranus and Neptune, which are made of hydrogen, helium and other gases. Despite being referred to as gas giants, intense heat and pressure towards their centres cause their gases to compress into liquid metal or rock.

5: Most Asteroids Found Between Mars and Jupiter

Asteroids are usually rocky or metallic in nature and in our solar system most can be found orbiting the Sun between Mars and Jupiter in an area known as the asteroid belt(2.7 AU). It is believed that in the early evolution of the solar system, this region once contained enough material to form a planet but Jupiter’s intense gravity stopped the materials from successfully coalescing into a planet.

6: The Closer To The Sun, The Hotter The Planet

In general the closer the planet is to the Sun the hotter is its average temperature. The average temperature of Mercury is a blistering +427 Celsius, but the planet Neptune’s average temperature is a chilly -200 Celsius. However, Venus (460c) is actually hotter than Mercurythanks to its thick carbon dioxide atmosphere which creates a greenhouse effect, whilst Mercury has a very thin atmosphere and so cannot trap the Sun’s heat very easily.

7: One Year Different On Each Planet

The closer the planet is to the Sun, the quicker is its annual orbit around our star. Whereas the Earth takes one year to revolve around the Sun, for instance, Mercury would complete its orbit in 88 days, while distant Neptune would complete its annual trek in 165 years.

8: Comets We See Originate From Within Our Solar System

The comets we see in the night sky come from our solar system and are either short-period, in which case they originate in the Kuiper belt (30 To 50 AU), or longer-period comets, in which case they originate in the Oort cloud. Comets are made of ice and dust and as they approach the Sun their surfaces warms up causing their materials to vaporize, thus producing a comet’s characteristic tail. In the process, numerous meteoroids are shed and spread out along the orbit of the comet such that whenever the Earth’s atmosphere passes this dust trail a meteor shower occurs, such as the Geminids and Leonids.

9: Nearest Star To Earth is Proxima Centauri

Outside of our own solar system, the nearest star to Earth is a red dwarf star called Proxima Centauri (4.24 light-years), followed by Barnard’s Star in the constellation of Ophiuchus (6 light-years). The brightest star in the night sky, Sirius (-1.46 magnitude) in the constellation of Canis Major, is the 5th closest star to Earth at a distance of 8.6 light years.

10: There Are 100 Billion Solar Systems In Milky Way Galaxy

In ancient times, the solar system was considered to represent the entire universe and the planets were believed to be ‘wandering stars‘ orbiting the Earth along with the Sun and stars. With the advent of the scientific revolution beginning in 1543, the Earth was later included in the list of planets but until recently astronomers still knew of only one solar system in the universe. Within the last 10 years or so, however, over 550 planets orbiting distant stars have been found and scientists now estimate that there may be as many as 100 billion solar systems in our own Milky Way galaxy, alone.