Planets Game Quiz Online

This page features a Planets Game Quiz Online. It is an exercise for students studying science in 3rd, 4th, 5th, 6th to 8th grades. There are 8 planets in total and each one has a unique characteristic. This game contains 15 questions which test students's knowledge on the different planets. Also consider playing other games in the 8th grade games section which individually cover the planets. This game is suitable for classrooms, is free and available at all times. Feedback at the end of the game tells you how much you know about planets. You can keep on practicing until you get all the answers right. Hit the "start" button.

 

Planets - Smallest to Largest

How many planets are there? How many planets are smaller than Earth? Which planets are dwarfs? Do dwarf planets exist? How big is the largest planet in the solar system? These are questions we can all ask ourselves. Here's a guide to the different sizes and masses of planets. The information presented here should give you a general idea of the relative size of planets in our solar system. If you're interested in learning more about our solar system and what makes it unique, read on!

 

Biggest planet in the solar system

Jupiter, the fifth planet from the Sun, is the largest planet in our solar system. The planet is a gas giant, with a mass over 2.5 times that of all the other planets in our solar system. Yet, it is still only a tenth the mass of the Sun. So, what is Jupiter's mass? Let's find out!  Jupiter is the biggest planet in our solar system and has dozens of moons, many of which are small. Its four largest moons are Ganymede, Europa, and Io, and they each have their own magnetic fields. Although most of Jupiter's moons are small, Europa and Io are the largest and most volcanic. While these moons aren't exactly Earth-sized, they are surprisingly close to Jupiter. The size of Jupiter is incredible, with an orbit that spans over a half-billion kilometers. It is so large that over one-third of Earth-sized planets could fit inside. However, some planets are even larger, containing more than a thousand Earths. 

 

How many planets are there

We know of eight major planets in our solar system, but how many others are there? The International Astronomical Union has defined the term "planet" and the terms "dwarf planet" and has reclassified Pluto from planet to dwarf planet. While this new classification does not change the number of planets in the Solar System, it does put to question the size of our solar system. According to the Drake equation, there are nine planets. There is also one asteroid, Ceres, which is larger than Earth and would become the fifth planet. And then there is the Kuiper belt, a region of icy/rocky bodies beyond Neptune. The Kuiper belt holds Pluto and another planet called 2003 UB313, known as the tenth planet. If the asteroid was a planet, it would have to be ten times larger than Earth to make it a viable candidate for life.

 

dwarf planets

The size and mass of dwarf planets varies widely. Pluto, Eris, Haumea and Makemake all fall into the category of dwarf planets. But hundreds more may also qualify. Dwarf planets are small enough to have life, but are far smaller than Earth. Pluto, for example, is just a fifth the diameter of Earth and has a mass of less than six hundred million tons.  Pluto and Ceres were discovered before the year 2006 and were named after Polynesian deities, namely Tehua, Hula and Rapa Nui. In fact, the names of these small bodies are very appropriate since they are all in the Kuiper Belt. Some of these dwarf planets, like Hygiea, are so close to Earth that they could potentially be considered asteroid candidates.

planets by mass

When talking about the size of the solar system, planetary mass is used to describe the size of a planet-like body. This mass is usually expressed in units of solar mass (the mass of the Sun), but there are also conventions used to measure the mass of extrasolar planets. Jupiter mass is the standard for the size of large gas giant planets, while smaller rocky terrestrial planets are measured in kilograms. During the study of the planets, children can compare scale models of the planets with the sizes of fruits and other items found on Earth. After comparing the weight of these objects, children can record their estimates in journals. To help children understand that the largest objects are the heaviest, they can group them by mass. Jupiter, Saturn, and the Earth are the biggest objects. Remember, however, that size and mass are not necessarily synonymous!

planets have rings

Why do planets have rings? Planets aren't the only objects in the universe that have rings. Some non-planetary bodies also have rings, but they aren't spheres and may have an asymmetrical orbital design. For instance, the centaur Chariklo orbits the Sun beyond Saturn and inside Uranus' orbit. Scientists suspect it formed in the Kuiper Belt region and migrated into the outer reaches of Uranus' orbit. The rings around Saturn are the largest of all planetary systems. They are roughly two billion miles across and 7,000 times the diameter of the planet. The outermost ring is so thick that it could fit a billion Earths! The rings of Saturn are named alphabetically by discovery date and contain varying amounts of material. The rings of Saturn's moon Enceladus are about 200 metres thick and are maintained by geysers of water. The rings of Jupiter and Neptune are largely composed of dust particles. Their structure depends on the planet's magnetic fields. The rings of Saturn and its moon Titan are made of a dark material called ammonia ice. Saturn has a thicker atmosphere than Earth's; its rings may be completely wiped out in 100 million years. Despite its size, Saturn's rings are not as spectacular as the ones of Neptune.

 

what planets rain diamonds

Scientists have long suspected that the planets of the outer solar system might rain diamonds. In the past, this was theorized by scientists based on observations and mathematical models. However, a recent study suggests that these diamond-covered planets are not the only possible candidates for diamond rain. Scientists from the U.S. Department of Energy's SLAC National Accelerator Laboratory also proposed the possibility of diamond rain on the planets of Neptune and Uranus. The idea that planets may rain diamonds is based on the general makeup of gas giants like Uranus and Neptune. Both these planets have dense atmospheres that are filled with methane (a greenhouse gas). Diamonds are formed under high heat and pressure, and the temperature on these planets is between 3,000 and 12,000 degrees Fahrenheit. The pressure is about 200,000 to 6 million times higher than on Earth. The outer layers of a planet contain a high concentration of carbon. These atoms react with hydrogen and carbon, forming diamonds. But they can't be harvested directly from the planet's surface. They're so cold and difficult to reach that no one can get them. Despite the immense pressure and temperature, diamonds can reach a centimetre in size. Even celebrities would want to own one of these diamonds!

planets farthest from the sun

When it comes to distances from the Sun, our outer planets, Jupiter, Saturn, Uranus, and Neptune, are the closest. Their orbits are so large and elliptical that they approach the Sun at nearly 4 billion km. The closest planet to the Sun is Mercury, but Earth,  Mars, Neptune, and Pluto are a bit farther away. But they all have something in common. Mercury is the closest planet to the Sun, and it has the largest core in relation to its size. As it solidifies, Mercury's massive core shrinks, leaving scarps in its surface. Mercury also has mottled surfaces, a result of something on its surface changing from solid to gas. However, Neptune is the furthest from the Sun.  The Sun is the largest object in our solar system, accounting for 99.8% of its mass. It is 864,938 miles in diameter and is extremely hot - its core is 15 million degrees Celsius! 

planets with water

Water is present in many forms throughout the solar system. The smallest, Mercury, is the closest planet to the sun, and its poles are often untouched by the heat of the sun, which allows ice to accumulate. The MESSENGER spacecraft snapped images of the ice caps on Mercury in October. Though liquid water is highly unlikely on Mercury, tidal forces from Jupiter keep the surface water warm. Other factors may also contribute to this phenomenon, such as hydrothermal vents. Some extraterrestrial planets may not have a definite surface, and their oceans could be hundreds of miles deep. Earth's deepest ocean is less than seven miles deep. If a planet were to contain water, pressures would be more than a million times greater than Earth's, creating strange phenomena at the surface, such as rock-like phases of ice. But it is difficult to say for sure.