Components of our solar system, with sizes to scale, but distances not.
© 2006 The International Astronomical Union/Martin Kornmesser
This team is studying the way planets form, and then evolve.
Here are the main working folders for material on this topic:
Insofar as the leading planetary model under consideration has planets as burned-out stars, planetary science is an appendage to stellar theory.
||pen ball point
||½ pin head
||US nickel (5¢)
||US penny (1¢)
In astronomy, it's easy to forget the significance of the vast distances separating objects in space. If the Sun was the size of a soccer ball, and if it was placed on the goal line, the Earth would be the size of a pin head, and it would be a quarter of the way down the field. Mars would be half that size, and near the 36 yard line, making it somewhat difficult to find in the grass. Jupiter would not even be on that field, but a quarter of the way down the second field (assuming that the fields were end-to-end), and it would be the size of a nickel — easier to find, but that's a long walk for a nickel. Saturn would be a penny, and 226 yards away. (Why bother?) Uranus would be just a little smaller than a chick pea, and halfway down the fifth field. And Neptune would be a green pea on the eighth field down. (From that distance, you wouldn't even hear the cheering on the first field.)
So there are four rocky planets (Mercury, Venus, Earth, & Mars), that are all on the same field as the soccer ball, and which are the size of a pin head or less. Then there are four gas giants (Jupiter, Saturn, Uranus, & Neptune), which are the size of a small coin or less, and which are several or many soccer fields away.
All in all, space is a pretty cold, dark, and empty expanse. Why anybody would want to go there is beyond us.