# How Well Do You Know Basic Facts About Our Solar System?

SCIENCE

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By: Deborah Beckwin

7 Min Quiz

# How old is our solar system?

Although it's not entirely clear how our solar system came to be, the most widely accepted theory is called core acceleration. Within a solar nebula (a rotating cloud of dust and gas), the sun was formed by gravity collapsing into the spinning nebula. Powerful solar winds pushed out the gases, leaving rockier materials closer to the sun and gases further away, giving us the planets and their compositions as we have them now.

# How far is the sun away from Earth?

From the center of the sun to the center of the earth is 93 million miles. This is also the unit of measure used to when measuring distances within the solar system.

# In astronomical units (AU), what's the distance between the sun and the edge of the solar system?

So 122 AU may sound abstract—how big is that? Even knowing that 1 AU is 93 million miles may not help, so here's the math: that distance is 9 billion miles.

# Earth is pretty far away from the sun, so approximately how long does it take for sunlight to reach us?

Even though we're 93 million miles away from the sun, light travels pretty quickly. If you want to do the math, it's 93 million miles divided by the speed of light, which is 186,282 miles per second—it's a little over 8 minutes, 30 seconds.

# The sun takes up how much of the total mass in our solar system?

The actual percentage is 99.86 percent of the known mass, which is 1.9891 × 10^30 kilograms. The bigger planets, Jupiter and Saturn, take up most of the rest of that percentage. To compare, Earth isn't a small little rock, with a mass of 5.972 × 10^24 kilograms—but it would take 1.3 million earths to fill the sun.

# Solar winds from the sun envelope the planets in a bubble of charged particles known as what?

Also known as the heliopause, the heliosphere's electrically conductive particles are in a plasma state, meaning the particles are highly responsive to electromagnetic forces. This plasmic bubble protects the planets from galactic cosmic radiation.

# When the sun has a solar flare or a coronal mass ejection, it affects Earth's magnetic field, which is known as what?

Earth's magnetosphere is essentially the planet's magnetic field, and between the four terrestrial planets, Earth's is the strongest. Created by the molten iron at Earth's core, the comet-shaped magnetosphere helps to protect us from solar winds as well as from solar and cosmic radiation.

# Within Earth's magnetic fields are two large areas of radiation. Do you know what they're called?

The charged particles in the Van Allen belts are considered to be trapped from solar winds as well as from cosmic radiation from other galaxies. There are two belts—an inner belt and an outer belt—which can change shape during solar storms. The belts have been studied by NASA for the past few years through probes, since radiation can affect astronauts, spacecraft and satellites.

# What is the name of the brightest star in our night sky?

Sirius is a binary star and is a part of the constellation Canis Major. Historically, the rising of Sirius on the eastern horizon is where we get the phrase the "dog days of summer," because it was associated several phenomena including drought, flash thunderstorms and rabid dogs.

# Officially, how many planets are in our solar system?

Until August 24, 2006, Pluto was considered to be one of the nine planets in our solar system. On that day, the International Astronomical Union (IAU) demoted Pluto from planet to dwarf planet. But it doesn't mean Pluto is no longer important, because earlier that year, NASA's New Horizons space probe project to Pluto and the Kuiper belt was launched, giving us new images and information about Pluto in 2015 and 2016.

# In our solar system, how many recognized dwarf planets do we have?

Currently, there are five recognized dwarf planets, meaning they're not a satellite or moon (orbiting a planet), but they're not a planet either (truly orbiting a sun). These are Ceres in the asteroid belt along with Pluto, Haumea, Makemake and Eris on the outer edge of the solar system. There are possibly hundreds to thousands more, but by IAU standards, these five are officially recognized as of 2008.

# What's another term for the inner planets (Mercury, Venus, Earth and Mars)?

Mercury, Venus, Earth and Mars are called terrestrial planets because of their composition. They're primarily made of rock and/or metal and have a solid surface. Other names for these four planets are telluric (Tellus is Latin for "earth") planets or rocky planets.

# What's another term for the outer planets (Jupiter, Saturn, Neptune and Uranus)?

Jovian planets relates to the Roman name for Jupiter, Jove. They're called the gas planets because they're primarily comprised of helium and hydrogen, along with other gases, and have no solid surfaces; but Uranus and Neptune are also called the ice giants because they are comprised more of heavier elements in frozen states such as sulfur, oxygen and carbon. Jupiter and Saturn are primarily comprised of helium and hydrogen and are sometimes called gas giants.

# Between which two planets is the asteroid belt located?

The asteroid belt, also called the main belt or the main asteroid belt, has minor planets and asteroids in between Mars and Jupiter. It forms a boundary between the inner and outer planets. The thickness of the belt is about 1 AU, but there's quite a bit of space between objects.

# From Neptune's orbit to around 20 AU beyond, there's a flat area of our solar system containing small solar system bodies (SSSBs). What is this area called?

The Kuiper belt (sometimes called the Edgeworth-Kuiper belt or the Kuiper-Edgeworth belt) contains millions of these icy SSSBs—leftovers from the creation of the solar system. They're also calls Kuiper belt objects (KBOs). Dwarf planets Pluto, Eris, Makemake and Haumea reside here.

# Theoretically, just outside of our solar system, there's a cloud of icy planetesimals, or objects made from rocks, dust and other things. What is this cloud called?

The spherical Oort cloud, also known as the Öpik–Oort cloud, is theoretically where long-period comets (such as Halley's comet) originate. The Oort cloud looks to be part of the remnants of the solar system's formation. This can be seen as our solar system's outer boundary in relation to the rest of the Milky Way and the universe.

# Which of the following planets is NOT named after a mythological god or goddess?

Earth is the only planet without a mythological name. Earth comes from the Old English word "eorthe," meaning ground or soil.

# What kind of star is the sun?

The sun is like most stars in the Milky Way and in the universe—a main sequence star. The central feature of main sequence stars is that at their cores, they convert hydrogen into helium, a nuclear fusion process which creates a massive amount of energy.

# Only one of these statements about Earth's moon is true. Do you know which one it is?

Due to the tidal forces from the Earth, the moon can actually have quakes—some shallow and some deep. Some of the quakes come from the impact of meteorites, and some quakes occur when the moon's crust is exposed to the sun again after two weeks in darkness, causing the crust to expand.

# Which is the least dense planet in our solar system?

Saturn lacks density is due to its outer layer, which is made of gas. And although the core is solid, comprised of rock, the planet's density makes it lighter than water, meaning it could float on water.

# Which planet is the hottest in our solar system?

Because Mercury has no atmosphere, it's actually the second-hottest planet in the solar system. And without an atmosphere to trap heat, the temperature fluctuations on Mercury can run about 1100 degrees Fahrenheit between day (800 degrees) and night (-280 degrees). Venus is slightly hotter due to its denser atmosphere, almost completely comprised of carbon dioxide, with temperatures reaching up over 860 degrees Fahrenheit.

# Venus' clouds are comprised mainly of sulfur dioxide and what other compound?

Venus' clouds are so thick, 60 percent of sunlight is reflected back into the universe. It was once hoped that, because Earth and Venus are similar and size, that life could be sustained on Venus, but the composition and thickness of these clouds alone would make it a harsh environment for human life—or any life.

# Which of these statements about Mars is NOT true?

Unlike Earth, Mars does not have a magnetic field because its core is solid—or, at the very least, partially solid. But it does have a magnetosphere; it's just not as substantial as Earth's is. That magnetosphere protect Mars' surface from solar winds.

# The nickname for which celestial body is "dirty snowball?"

Comets are made of some rocks along with icy material, such as frozen water, ammonia or methane. Comets seem to come from the Kuiper belt and the Oort cloud. Another nickname for the "dirty snowball" is the "cosmic snowball."

# What is the technical term for a shooting star?

Meteors typically come from asteroids, but they can come from other places, such as the moon or Mars. There are three general composition types: metallic (i.e., they contain iron), stony or a mixture of stone and iron. If it lands on the surface of a planet, it becomes a meteorite, but if it burns up in the atmosphere, then it's a meteor.

# Which one of these statements is NOT true about Jupiter?

Jupiter indeed does have rings (albeit faint ones)—in fact, all the outer planets do. Mainly comprised of dust, the rings of Jupiter were first seen via the Voyager 1 probe in 1979 and have been observed and researched since then.

# Which planet was first thought to be a comet?

Uranus was discovered by astronomer William Herschel in 1781. He then realized that the path this "comet" was taking was more circular and less elliptical than a comet's path. Uranus' rings weren't discovered until almost two centuries later, in 1977.

# Which planet is the smallest of the four outer planets?

Neptune may be the smallest planet of the outer planets, but it's the windiest of our solar system, with wind speeds of up to 1,200 mph. Neptune is also the densest of the gas planets with possibly extremely hot oceans kept in place by exceedingly high pressure.

# Which of the dwarf planets sometimes ends up being closer to the sun because of its eccentric orbit?

What caused scientist to demote the planet was its location in the Kuiper belt, surrounded by bodies called plutoids. Because of those bodies, astronomers believed that Pluto didn't fully own its transit. Months before that decision, the New Horizons space mission began, and in 2015 and 2016, we've received updated data and pictures on this now dwarf planet.

# Which planet was considered to be an asteroid until 2006?

Ceres is the largest body located in the asteroid belt and was first seen as a comet by Italian astronomer Giuseppe Piazzi. And then it was thought to be a planet but then was later classified as an asteroid in 19th century. In 2006, when Pluto was considered to be reclassified, Ceres was also considered to be reclassified—but both planets didn't meet the full criteria for a planet and received a dwarf-planet classification.

# This dwarf planet was discovered in 2005.

Named after the Rapa Nui goddess of fertility, Makemake was discovered in 2005 and classified as a dwarf planet in 2008. Not much is known about Makemake yet, but in 2016, the Hubble Space Telescope found a small moon with a radius of 50 miles, nicknamed MK2.

# Which of the dwarf planets is the first Kuiper belt object found to have rings?

Named after the Hawaiian goddess of fertility, Haumea was discovered in either 2003 or 2004—and it depends on who you ask, because two teams are claiming the discovery. Because Haumea spins so quickly, it has more of an oblong or oval shape and it has a very short day—only four hours. It was classified as a dwarf planet and officially named in 2008.

# Because this object appeared to be larger than Pluto, it set off a debate that caused the IAU to more clearly define what a planet is.

Aptly named after Eris, the Greek goddess of strife and discord, this celestial body is what sparked the fierce debate about the definition of a planet (which, by the way, the debate has not been completely resolved). Eris was discovered in 2003 by the same Palomar Observatory team that discovered Makemake in 2005. This dwarf planet and its moon Dysnomia are the furthest from the sun, as it is beyond the Kuiper belt.

# What is the name of a hypothetical planet deep in our solar system?

In 2015, researchers at Caltech announced that, based on mathematical modeling (not by observation), there is evidence of a large planet which is in a quite long orbit in our outer solar system, which would explain the orbits of five objects in the Kuiper belt. As astronomers search for this planet via powerful telescope, they've dubbed it "Planet Nine," but the typical placeholder name for a planet beyond Neptune is Planet X.

# Which galaxy is closest to the Milky Way?

Appearing in the constellation Andromeda, the Andromeda Galaxy (Messier 31 or M31) is our closest galactic neighbor, about 2.5 million light-years away from Earth. And four billion years from now, the Milky Way and the Andromeda Galaxy will combine and become the Milkomeda Galaxy. Also our largest neighbor, the Andromeda Galaxy has approximately one trillion stars with the span of 220,000 light-years.

# Explore More Quizzes

Image: Suchart Kuathan/Moment/Getty Images

The universe that we live in is a vast and ever-expanding place, expanding faster than the speed of light. And the calculations made in astronomy and cosmology are so large, it can be hard to comprehend how big the universe actually is.

Within our universe, there are at least 100 billion galaxies—and that's in the observable universe. If the universe expands faster than the speed of light, then that means there will be galaxies that we are unable to see.

And in each galaxy, there are at least 100 billion stars.

On top of that, there could be multiple universes with at least as many galaxies as we have in ours.

And in that intergalactic soup of the billions of galaxies and stars is where we live—the Milky Way, the spiral disk of stars (at least 200 billion to possibly 400 billion stars) which contains our solar system. And our solar system is not the only one. Scientists have found at least 500 solar systems within our galaxy. But just within the Milky Way alone, there could be up to 100 billion solar systems.

Even just looking at our own solar system is enough to make one's mind implode with numbers that require scientific notation because there are just so many zeroes. But that's what this quiz will attempt to do—to test your knowledge on the basics of our solar system, one of possibly billions in a galaxy with billions of stars, in a universe with billions of galaxies.

If you're ready to take this fantastic voyage through the place we call home, then let's liftoff! Have fun and good luck!