Pin Me

A Guide to the Solar System

written by: Arlene McKanic•edited by: Paul Arnold•updated: 9/12/2011

Planets and planetoids, asteroids called Trojans and Centaurs, dwarf planets and plutoids, meteors, comets, extra terrestrial volcanoes and volcanoes made of ice! Moonscapes beautifully pockmarked with craters and valleys, and course, our endlessly interesting Sun! Let's explore the solar system!

  • slide 1 of 2

    The Solar System

    The Solar System formed about four and a half billion years ago out of a collapsing cloud of gas that might have been the result of another star going nova. The Sun, though its an average dwarf star, makes up 99 percent of all the matter in the solar system. The temperature at its core is about 27 million degrees F, and its surface temperature averages about 11,000 degrees F. Since it’s a ball of gas, different parts of the Sun have different rotational speeds, and its equator spins faster than its poles.

    There are officially eight planets, after Pluto was demoted to a dwarf planet in 2006. All of them have natural satellites except for Venus. Some of these moons, like the volcanic Io, are fascinating in and of themselves.

    The asteroid belt lies between Mars and Jupiter, and is made of tens of thousands of tiny planetoids. Most are bits of debris no bigger than grains of sand, though Ceres is 485 miles in diameter. Ceres, named after a Greek goddess, was discovered on January 1,1801 by Giuseppe Piazzi, the director at the observatory in Palermo in Sicily. Since then, more and more asteroids have been discovered and given names like Eunomia, Interamnia, Euphrosyne and Bamberga.

    The Kuiper belt is another band of objects and is found beyond Neptune; astronomers now classify the former planet Pluto as one of these objects. Beyond the Kuiper belt is the Oort cloud, which is said to be where comets originate from.

  • slide 2 of 2

    The Only Solar System Table of Contents You'll Ever Need!

    Comparing the Sun and the Earth

    Of course the Sun is a star and the Earth is a planet. What are the differences and similarities between them? Some are obvious, but some are not!

    Interesting Facts About the Sun

    Scientist like to brag that the Sun is an average dwarf star. But, as with all those brightly glowing gaseous bodies, there’s a bit of weirdness going on with it as well. Sunspots and faculae: compare and contrast.

    Our Solar System: Planets, Moons, Asteroids, Comets

    Though the distances may be vast from our tiny human perspective, our solar system is just chock full of stuff. There are comets the size of Manhattan, and moons that might have oceans of water beneath their icy crusts. Even the Earth still has her secrets.

    Some Very Unusual Solar System Facts

    Space can be surpassingly, wonderfully odd, and our solar system, docile though it seems, is no exception. Some of the facts are just a bit deliciously hair-raising! What for example, is an ice volcano?

    19 Fun Things to Know About the Solar System

    Nineteen fun things that’ll make you want to hijack the nearest starship and go exploring. Discover which planet has the longest day and which has the shortest. And besides Pluto, what is a plutoid?

    Terrestrial Planets, Jovian Planets

    The first bunch are like Earth, which means they’re small and rocky. The second are like Jupiter, which means they’re big and gaseous. And guess which planet could float in a bath tub if there was a bathtub big enough for it?

    A Journey to the Inner and Outer Planets of Our Solar System

    There's more, much more to the planets that well ever see through a telescope, and we are learning new things every day. Which planets, for example, have Earth-sized icy cores? Does Pluto really not have what it takes to be a planet?

    Planets in Physical Science

    The science of the planets isn’t that complicated. It’s all Newtonian. But then, Newton did invent calculus, didn’t he?

    Facts About the Inner Planets of the Solar System

    Here’s one: they're small and made out of rocks. But of course, that’s not all. At least one of them has life. As for the others, time will tell.

    The Geology of Other Planets in Our Solar System

    The tallest mountain in the solar system isn’t on Earth. One planet changes its topography all the time just because of the heat and pressure of its atmosphere. And do check out the craters and valleys and mares and planitias that abound.

    What is a Planet?

    A good question, especially since the IAU demoted Pluto. Some folks are still in mourning. But are there any new would-be planets out there?

    Facts About Pluto, the Dwarf Planet Discovered by Clyde Tombaugh

    We know surprisingly little about Pluto, named after the god of the netherworld. Except, of course, that it’s little.

    The Ninth Planet: Where is Pluto, When and Why Was It Demoted?

    Get all the facts on why Pluto was demoted and is a planet no more.

    Is Pluto a Planet or a Dwarf Planet or is it a Plutoid?

    Could it possibly be all of the above? Ah, if only Pluto could talk. Or better yet, write its own book.

    Eris the Dwarf Planet: Facts and Information

    This dwarf planet was named after the goddess of discord. She even has a moon, Dysnomia, named after the goddess of lawlessness. Eris used to be called Xena, after the warrior princess. What was wrong with that name?

    The Description and Nature of Kuiper Belt Objects

    Who was Kuiper, and why did he have a belt named after him? Where is the Kuiper belt? And just what sort of things can be found there?

    The Myth About the 10th Planet in the Solar System

    Is this the planet that comes around the solar system once in a millennium to cause havoc? Or is it another one? Read and find out.

    Asteroid Belt Facts

    Why the asteroid belt is different from the Kuiper belt, and why neither of them are the Oort Cloud. One of the asteroids is named for a cat named for Mr. Spock. Fascinating.

    Jupiter's Asteroidal Escorts -- The Trojan Asteroids

    You’ve got to find out why these asteroids are called Trojans. Why don't they smash into Jupiter more often than they do? And just where are they escorting Jupiter, anyway?

    Minor Planets or Asteroids - Their History and Classification

    From Ceres to Makemake and beyond, you’ll find out what these objects are made of, where they’re going and where they’ve been. Most have their own moons. A surprising number were named after fertility deities, though it's mighty cold and sterile out where they are!

    What Are Planetoids? Asteroids, Centaurs, Trans-Neptunian Objects

    Though sometimes Neptune is even farther away from the Sun than Pluto, the planet is by no means lonely. Centaurs are little planetoids with wobbly orbits between Neptune and Jupiter. And Pluto gets yet another title: Trans-Neptunian object!

    When Was the Asteroid Belt First Discovered?

    Like a lot of scientific discoveries, the asteroid belt was theorized before it was actually discovered. The Titius-Bode law said there had to be something between Mars and Jupiter. They were right!

    Beyond the Asteroids -- Kuiper Belt Objects

    Some think they’re what’s leftover from the formation of the solar system, and they can tell us much about our place in the cosmos. It's so cold out there that even ammonia and methane are frozen. This alone makes the Kuiper belt a very interesting place indeed.


    This planet takes 11,000 years to go around the Sun. And it’s still part of the solar system. Planet X, or no?

    The Oort Cloud

    The Oort cloud is named after the Dutch astronomer Jan Oort. Some believe the Oort Cloud is where comets originate before they begin their journey around the Sun. Find out more about this mysterious halo around our solar system.