Top 10 Facts About Our Solar System

The 8 Planets of The Solar System
The 8 Planets of the Solar System - Credit: Rogelio Bernal Andreo/Stocktrek Images

The “solar system” is simply the name of our own planetary system. Our solar system consists of 1 central star and the smaller objects that orbit it in space, including 8 planets, 200+ moons, 4,584 known comets, and more than 1 million asteroids. It is 4.6 billion years old, and 99.86% of the solar system’s mass is contained in our Sun, a rotating yellow dwarf star whose powerful gravity exerts an influence across 2 light-years of space.

Let us explore some more interesting facts about the solar system that are sure to amaze!

10 Amazing Solar System Facts

  1. Our solar system has eight planets
  2. Uranus is the only planet named after a Greek god
  3. Five planets are visible with the naked eye
  4. The solar system contains more than 200 moons
  5. There are 5 dwarf planets in our solar system
  6. Contains 3 regions of concentrated space junk
  7. All comets come from the outer solar system
  8. Our solar system is part of the Milky Way galaxy
  9. Sunlight takes over a year to leave our solar system
  10. Our nearest planetary system is 4.24 light-years away

1. Our solar system has eight planets

The 8 planets of our solar system are divided into the inner planets Mercury, Venus, Earth, and Mars, and the outer planets Jupiter, Saturn, Uranus, and Neptune. The inner planets, so named because they orbit closest to the Sun, are solid balls of rock and metal, while the outer planets with orbits beyond the asteroid belt are basically giant balls of gas. Despite being called gas giants, intense heat and pressure cause their gases to compress into liquid metal or rock near their centers.

Our solar system planets move around the Sun in elliptical orbits, and the closer a planet is to the Sun, the quicker its annual orbit around our star. For example, the Earth takes one year to revolve around the Sun, Mercury completes its yearly orbit in 88 days, while distant Neptune completes its annual trek in 165 years.

2. Uranus is the only planet named after a Greek god

All of the solar system planets are named after Roman Gods except Uranus, which takes its name from the Greek god of the sky Ouranos. If the planet was named after its Roman equivalent, it would have been called Caelus.

Here are some more fun facts about each solar system planet presented in order of their distance from the sun. What is a simple way to remember the solar system planets in order? My Very Easy Method: Just SUN.

  • Mercury – smallest planet (3,031.9 mi. diameter), shortest year (88 earth days)
  • Venus – hottest planet (471°C), longest day (243 earth days)
  • Earth – only planet with surface water and life
  • Mars – biggest volcano (16 mi.), most explored
  • Jupiter – biggest planet (43,440.7 mi. radius), shortest day (9 hr 55 min)
  • Saturn – least dense (687 kg/m³), most moons
  • Uranus – largest tilt (98 degrees to orbit), only planet named after a Greek god
  • Neptune – coldest planet (-214 °C), longest year (164.8 earth years)

3. Five planets are visible with the naked eye

There are 5 naked-eye planets, and these so-called “wandering stars” that move relative to the “fixed stars” have been known since antiquity. In the 1600s, the invention of the telescope then ushered in new planetary findings with first Uranus (1781) and then Neptune (1846) discovered. Pluto was also found in 1930, but in 2016 it was downgraded to dwarf planet status by the International Astronomical Union (IAU).  Over time, the Earth was also recognized as being just another planetary body circling a central star in space.

Planet Venus in the sky
Photo of Venus by Aditya Chache

Mercury is the hardest naked eye planet to see, while Venus is the night sky’s second brightest object and, therefore, the easiest to spot. Being closest to the Sun, they can both be seen around sunrise and sunset. Mars looks bright and has a notable red coloring, Jupiter is white and the sky’s third brightest object overall, while Saturn looks like a bright off-white star.

Admittedly, those with excellent eyesight may be able to see Uranus, but the planet is very faint with an apparent magnitude that ranges from just 5.7 to 6, which is why it remained unknown for so long.

4. The solar system contains more than 200 moons

Galilean Moons
Jupiter’s four Galilean Moons by NASA

There are more than 200 moons in our solar system with most of the planets, except Mercury and Venus, having their own natural satellites. Moons don’t just orbit planets, though and some dwarf planets and asteroids have their own natural satellites. The dwarf planet Pluto, for instance, has five known moons, including Charon which is around half the size of Pluto, while the asteroid 130 Elektra has three minor moons circling it.

Jupiter has 79 known moons, including Io, Europa, Callisto, and our solar system’s biggest moon Ganymede, which is even bigger than the planet Mercury. Saturn also has a similarly high number of moons, with the solar system’s second largest moon Titan roughly half the size of Earth’s Moon.

The Red Planet, Mars, has two moons called Phobos and Deimos, the latter of which is the smallest found to date, although new moons and record candidates are being found all the time.

5. There are 5 dwarf planets in our solar system

There a currently just five officially classified dwarf planets in our solar system recognized by the International Astronomical Union. These are Ceres, Pluto, Haumea, Makemake, and Eris, although many more potential candidates also exist. Of these, Ceres is the only one located inside the asteroid belt, while the other dwarf planets are found near the Kuiper belt.

Unlike the planets which have cleared their orbits of smaller objects, dwarf planets do not have enough gravity to clear their neighboring region of planetesimals through collision, capture, or gravitational disturbance.

6. Contains 3 regions of concentrated space junk

The prevailing origin story of the solar system is that the Sun and planets formed from a cloud of gas and dust called a solar nebula. There are three main structures in our solar system that are composed of remnants from the solar system’s early formation, namely the Asteroid Belt, Kuiper Belt, and Oort Cloud.

Between Mars and Jupiter lies the Asteroid Belt, a doughnut-shaped region that consists of rock, stone, and metal in lesser amounts. 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.

Beyond Neptune is found the Kuiper Belt, a disk-shaped region similarly containing objects that might have formed a planet had Neptune’s gravity not prevented the small, icy objects there from coalescing into a large planet. Finally, the Oort Cloud lies beyond Pluto and is thought to surround the entire solar system as a sphere of icy objects.

7. The comets we see all originate from the outer solar system

There are currently around 4,500 known comets in our solar system, although that number is likely to be significantly higher. The comets we see in the night sky are either short-period (less than 200 years to orbit the sun), in which case they originate in the Kuiper belt, or are long-period comets (more than 200 years to orbit the sun), in which case they originate in the Oort cloud.

Halley’s Comet is the most famous comet from the Kuiper Belt, and probably the most famous comet of all. It has an orbit of around 76 years and is next expected to be visible from Earth in 2061. Comet Hale-Bopp is a famous long-period comet from the Oort Cloud with a huge orbital period of 2,533 years. It was last seen in 1997.

Halley's Comet
Image Credit: Halley’s Comet by NASA

Comets are made of ice and dust, and as they approach the Sun their surfaces warm 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.

8. Our Solar System is part of the Milky Way Galaxy

Milky Way's 100 billion solar systems

The solar system is part of the Milky Way galaxy. While there may be more than 250 billion stars in the Milky Way, until recently, astronomers knew of only one planetary system, our own. That changed in 1992 when radio astronomers detected two rocky planets orbiting a pulsar in the constellation of Virgo.

Since then, over 700 other planetary systems have been discovered, and in 2022 the James Webb Space Telescope was also able to capture the first direct image of a planet outside of our own solar system. Scientists now estimate that there may be as many as 100 billion solar systems in our own Milky Way alone.

9. Sunlight takes over a year to leave our solar system

The Sun lies at the center of our solar system and is a huge glowing ball of plasma, or highly ionized gas located 93 million miles (150 million km) away from our own planet. The Sun’s immense gravity means a photon of light can take 100,000 years to travel from its core to its surface, after which, traveling at the speed of light (186,282 miles per second), sunlight is able to cross the vacuum of space and reach us in just 8 minutes and 20 seconds. That time increases to 13 minutes for the planet Mars, 4.5 hours for the outermost planet Neptune, and more than a year to reach the Oort Cloud’s outer edge and beyond our solar system.

10. Our nearest planetary system is 4.24 light-years away

The closest solar system to our own is Proxima Centauri, which is part of a triple-star system called Alpha Centauri. Proxima Centauri is a red dwarf star that hosts three confirmed planets, one of which orbits within the star’s “habitable zone.”

Image Credit: NASA/Penn State University

It is also found 4.24 light-years away or 25 trillion miles from Earth. To put that vast distance into perspective, the Voyager 1 spacecraft currently traveling at 35,000 miles per hour would take around 70,000 years to reach our nearest stellar neighbor. It, of course, would have entered Proxima Centauri’s planetary system a long time before then, though.

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