Can You Pass This Elementary School Solar System Test?


By: Maria Trimarchi

6 Min Quiz

Image: shutterstock

About This Quiz

Maybe you were taken in from stories of a long time ago, in a galaxy far, far away ... Or maybe you desired to boldly go where no one has gone before. When you look up at the sky on a clear night, you'll see endless stars, our moon, maybe another planet shining back at you. Maybe you became interested in celestial bodies when you first found The Big Dipper, which is part of a constellation called Ursa Major. Or when you saw the three brightest stars in Orion's Belt: Rigel, Betelgeuse, and Bellatrix.

Scientists believe our solar system, which is called simply the Solar System, was formed when a giant cloud of dust and gas collapsed under the weight of its own gravity. And, when doing so, it began moving in a big circle -- creating and then spinning around a small star that would eventually become our sun. The galaxies, planets (including Earth) and other objects we see (and don't yet see) in our solar system, including dwarf (minor) planets, moons, comets and asteroids (and leftover dust and gas), were also formed in this event. And objects still unknown. For instance, did you know scientists think there could be a giant but undiscovered planet lurking around Neptune?

And there's more in our solar system than just that -- in fact, just spinning around our own planet there's an estimated 500,000 bits of orbital debris measuring between one and 10 centimeters in diameter and an additional 21,000 bits of debris larger than 10 centimeters. (If it sounds like it's getting a bit cluttered up there in space, it kind of is.)

Think you know a lot about Earth and our moon? Test your knowledge about our planet, and see how much you know about the basic elements and objects found in our galaxy and in our solar system.

How many planets are there in our solar system, that we know of?

As we know, there are eight planets in our solar system. Because some planets are visible to the naked eye, some of the other eight were known to ancient civilizations -- which means we don't exactly know which planet was the first to be discovered and by whom.


What is the third planet from the sun?

In the order of planets from the sun, with Mercury being closest and Neptune the most distant, it's Earth that's in the third position.


Is the sun a comet, a planet or a star?

The sun is a star. When a star has planets orbiting around it, we call it a "sun."


How many moons does Earth have?

Some planets in our solar system have more than one moon. Some have none. Our planet Earth has one moon, which is believed to have been created when the Earth was in a collision with a large, Mars-sized object.


What is the name of the galaxy that contains our solar system?

The Milky Way is our home galaxy, and our solar system is located in the area known as Orion's Arm. It's a spiral galaxy, which is the most common type.


All but one of the 8 planets is named for Greek and Roman gods. Which isn't?

Neptune is named after the Roman god of the sea. Venus, for the Roman goddess of beauty and love. And Mercury was named for the Roman god of travel. Earth, however, doesn't correspond to any name of an ancient god -- it's a word derived from English/German, and means "ground."


Which planet is known as the 'Red Planet'?

On Mars, the rust in the rocks of the landscape gives the planet a rusty-red appearance. You can look for it yourself -- it appears bright orange-red in our night sky. No telescope needed.


Which is the hottest of the planets?

Although it's not the closest planet to the sun, it's Venus that's has the hottest temperatures. It's because of the thick cloud cover -- the cloud cover, which is formed of carbon dioxide and other gases, prevents heat from the sun from escaping its atmosphere.


Which planet is the coldest planet in our solar system?

It's easy to assume that because Neptune is the farthest planet from the sun, it would also be the coldest planet. It does get cold there -- -360 degrees Fahenheit -- but it's actually Uranus that has the lowest recorded temperature, at -371 degrees Fahrenheit.


What force keeps the Earth and all the planets in orbit around the sun?

It wasn't until Isaac Newton published his "Theory of Universal Gravitation" in the 1680s that we began to understand the idea of gravity, and that it's a predictable force that acts on all matter across the universe. Today, still, though, it's still the least understood of the four fundamental forces of nature, which also includes strong force, weak force, and electromagnetic force -- but we do understand that it's gravity that keeps the Earth, moon, and all the planets and large objects in orbit around the sun.


In 2006, which planet was reclassified as a "dwarf planet"?

In 2006, the planet Pluto was downgraded from planet to dwarf planet, joining Ceres, Eris, Haumea and Makemake. Pluto is much smaller than the other planets, and is only about two-thirds the diameter of Earth's moon.


What is a black hole?

Black holes are what remains when giant stars explode at the end of their lives. Their gravity is so strong that nothing can escape -- and that includes light. In fact, black holes are invisible to us because they don't reflect light.


Which is the only planet that rotates on its side?

Uranus is the only planet that rotates on its side. Scientists still don't know the reason, but believe it may have been involved in a powerful collision, or collisions, in its history.


What's the difference between a terrestrial planet and a gas giant?

Terrestrial planets are mostly made out of rock and metal, whereas gas giants, as they're called, are made of hydrogen, helium and other gases. Terrestrial planets are also closer to the sun than the gas giants.


How long does it take light from our solar system's sun to reach our planet Earth?

Sunlight doesn't instantly shine on our planet when the sun comes up. It takes eight minutes for the light from the sun to reach Earth.


On which planet does the sunset appear blue?

If you were to watch a sunset on Mars, you'd notice something quite different from how it appears here on Earth. Because of the frequent dust storms on Mars, the sunset appears blue.


Which is both the biggest and the heaviest planet in our solar system?

It's Jupiter that's is the biggest and heaviest planet in our solar system. Its mass is more than 300 times the Earth, and in diameter, it's about 11 times our planet's size -- and you could fit more than 1,000 Earths inside it.


Which is the smallest and lightest planet in our solar system?

Mercury is a rocky, crater-covered planet with a thin atmosphere. It's the smallest known planet in our solar system, and only about as big as Earth's moon.


What shape is planet Earth?

Astronauts may have nicknamed it the Blue Marble, but the Earth actually isn't a sphere -- at least, it's not a perfect sphere. It's a slight ellipse, called an oblate spheroid, which means it bulges a bit at the equator and is flattened a bit at the north and south poles.


Which planets aren't visible from Earth without a telescope?

Mercury, Venus, Mars, Jupiter and Saturn are the brightest planets, and you can see these without binoculars or a telescope. Neptune, though, which is 2.7 billion miles away from Earth, and Uranus, which is 1.7 billion miles from Earth, can only be seen with a telescope.


Which planet is called Earth's "sister planet"?

Because Earth and Venus are similar in size, mass, composition (what they're made out of), and gravity -- and they're neighbors -- they've been nicknamed "sister planets." But the similarities end there. A single day on Venus is the equivalent of about 117 days on Earth. And the climate? The average temperature on the surface of Venus hovers around 864 degrees Fahrenheit.


Which two planets in our solar system don't have a moon?

Earth has one. Mars has two. And all the other planets in our solar system have at least one moon except for Mercury and Venus -- neither have even one moon, as far as scientists know.


What is a constellation?

Constellations are groups of stars that form patterns that we see in our night sky. There are 88 official constellations, including Cassiopeia, Orion and Ursa Major.


It's impossible to walk on the surface of which planet?

Four planets in our solar system -- Jupiter, Saturn, Uranus and Neptune -- don't have a solid surface. Because you can't walk on gases like hydrogen and helium, you can't walk on the surface of these planets.


Which of the four planets known as the "gas giants" has rings?

Saturn's long been known for its bright and colorful rings. But it's not the only one of the giant gaseous planets to have them. Jupiter, for instance, has a thin, dark ring. Neptune's rings are dark, as are the nine rings around Uranus.


What is the most abundant element in our universe?

Hydrogen is the most common and abundant element in our universe, followed by helium. In fact, together, hydrogen and helium make up 99 percent of the universe.


Saturn has 53 confirmed moons. What is the name of its largest moon?

Saturn's largest moon, Titan, was discovered in March 1655. It's the second-largest moon in our solar system -- and even has its own atmosphere (you expect that from a planet, but it's pretty unusual for a moon).


What are shooting stars, really?

Meteoroids are small pieces of rock or bits of dust that burn up when they enter the Earth's atmosphere -- which happens at speeds faster than 45,000 mph. During a night of stargazing, you can expect to see a shooting star about every 10 to 15 minutes.


What is the layer of gases that surround a planet called?

The layer of gases surrounding a planet is called the planet's atmosphere. Each planet has a different atmosphere. For instance, nitrogen and oxygen make up most of Earth's atmosphere, whereas Mars' atmosphere is mainly carbon dioxide. Mercury is the only planet that doesn't have a detectable atmosphere.


Where in our solar system do temperatures reach 10,000 degrees Fahrenheit?

The outermost layer of the sun, called the corona, experiences temperatures of about 900,000 degrees Fahrenheit. But at its core, which is where nuclear reactions happen to convert hydrogen to helium -- and that's what ultimately creates visible light on the surface -- temperatures are as high as 27 million degrees Fahrenheit.


What is the real name of the star we called "the North Star"?

Polaris, which is the brightest star in the Ursa Minor constellation, is known as the North Star. It sits very close to the north celestial pole -- and because it is nearly in a direct line with the axis of the Earth's rotation above this pole, it appears to stand motionless while the other stars in the northern sky rotate around it (it doesn't, but it looks that way!).


Stars shine a steady light. So, then why do they appear to twinkle in our night sky?

Stars twinkle in our night sky because the light they shine gets a little bent by the movement of air in the Earth's atmosphere. And that, to our eyes, looks like a twinkle -- which is called stellar scintillation.


The main asteroid belt contains the four biggest asteroids: Ceres, Vesta, Pallas and Hygiea. Where is it?

Long ago, in 1596, German mathematician and astronomer Johannes Kepler discovered what he considered to be a gap that was too large between the orbits of Mars and Jupiter. He was on to something; this is the asteroid belt, where Ceres, Vesta, Pallas Hygiea and many other asteroids orbit the sun.


What is the band of icy space debris on the edge of our solar system known as?

The Oort Cloud is on the very edge of our solar system, and too far away to see even through our most powerful telescopes. It's believed to be a thick shell, or bubble, of icy space debris that functions as the boundary of the sun's gravitational pull -- it's where objects that orbit the sun turn around and return on their trip back toward the sun.


Scientists estimate our universe is how old?

In 2013, NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and The European Space Agency's Planck spacecraft measured the age of the universe to be 13.8 billion years. Earth and all the planets in our solar system are estimated to be 4.6 billion years old.


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