BellaOnline Forums Education Astronomy Planets of the Solar System - Quiz *new article*

How well do you know the planets of the Solar System? Here's a beginner's quiz for you to test your knowledge. It's complete with answers and some more facts about the planets.

Planets of the Solar System - Quiz

The mass of Jupiter is over twice that of the other planets combined. In fact, if you included the moons and asteroids with the planets, that would still be true. In terms of volume (size), Jupiter is also bigger than all of the other planets put together. In this diagram you can see how big Jupiter is compared to the other planets.

Can you identify the planets that aren't labeled?

This diagram is scaled to show the relative distances of planets from the Sun. You can see that the inner planets are comparatively close together. By definition, Earth is 1 AU from the Sun (150 million km/93 million miles) and Mercury and Venus are closer than that.

Some of the labels may be confusing. Two of them show the distance in kilometers using scientific notation. Mars is 1.5 AU from the Sun. Jupiter (no label) is about 5 AU.

The Sun and planets aren't on the same scale as the distances. There is such an enormous difference between the two scales, you couldn't get them in the same diagram. However the Sun and planets are shown at their approximate sizes relative to each other. (The whole Sun still doesn't fit on the diagram!)

In my article How to Tell a Planet from a UFO, I give an example of confusion caused by Venus.

There are five planets easily seen from Earth with the unaided eye. And of course we can also see the Sun and the Moon - these were counted as planets at one time. People have been able to see all of these things ever since they starting looking at the sky, i.e., back into prehistory.

But in 1781 William Herschel, German-born British astronomer, found a new planet. It's the one we call Uranus, named for the father of the god Saturn. The discovery doubled the diameter of the known Solar System.

I imagine that everyone realized that Saturn is the planet with the brightest rings. After all, Saturn is famous for its rings. But you may have been surprised by brightest, since that implies that other planets have rings too. But we have four planets with rings, they're quite common.

1. Jupiter's rings were discovered by NASA's Voyager 1 spacecraft in 1979. They're dark and dusty and hadn't been seen by earthly telescopes.

2. Uranus has 13 rings and they're thinner and darker than Saturn's. We learned more about them from the Voyager 2 spacecraft, but astronomers learned of their existence in 1977 while observing Uranus occulting (passing in front of) a star.

3. Neptune's rings were discovered in 1984 by astronomers using the La Silla observatory in Chile and photographed five years later by Voyager 2. There are five narrow rings made mostly of dark dust.

As with the planet Herschel discovered, originally Neptune was called by various names. But finally it was agreed to stay with the classical theme.

And although Galle and LeVerrier (rightly) get the credit for the discovery of Neptune, there is evidence that a number of people had already seen it. However they all assumed it was a dim star and didn't pay it any attention. "Who Discovered Neptune" tells the story.

This graphic of the Solar System by Marcus Chown shows that moons are common. Mercury and Venus, all on their own, seem quite bereft. It may be that as the planets nearest the Sun, the Sun's gravity disrupted any formation of a moon. If so, Earth was quite lucky.

The pictures are, of course, pretty much the same size and not to scale.

Last month the US Post Office issued a pane of forever stamps showing images of the planets from half a century of space exploration. Superb.

Image credit: USPS/Antonio Alcalá © 2016 USPS

Mona, the stamps are stunning. I always purchase commemorative stamps and I snatched these up the moment I saw them.