Heavenly Bodies
Childhood is the perfect time to start learning about the different planets and their properties. Explain that not all planets are solid and that Earth is not the largest one. You should show your child the different pictures of the planets and their names. You can also identify some of the moons associated with each planet. Finish by educating her on the placement of the planets in reference to the sun. Allow her to experience the planets firsthand by letting her peer through a telescope.
Constellations
The different constellations have interesting stories that can fascinate a child. Share the truth about the constellations -- that they are just groups of stars and don't always look like the designated image -- and then inform him of the different stories of each constellation. This teaches the child a little something about the beliefs and myths of ancient cultures as well as some of the well-recognized star systems. Explain how over time, stars die, which may one day, in the far-distant future, completely erase the recognized constellations from the sky.
A Star's Lifeline
Although a small child may not be able to comprehend millions of years, it is still a good time to teach her about the life cycle of stars. Explain that every star has only a prescribed amount of time to live before it burns out like a candle. Don't make a point of telling her that the sun is a star just like any other, though -- this may cause her undue stress about events millions of years in the future, which will distract her from the rest of the lesson.
Types of Galaxies
There are three main types of galaxies for your child to learn about. Your home galaxy, the Milky Way Galaxy, is a spiral galaxy like many others. There are also the common elliptical galaxies, which come in either a circular or a cigar shape. Finally, there are the irregular galaxies, which, as their name suggests, don't have a defined shape. Explain the three different types of galaxies to your child and draw some illustrated demonstrations of each type so your child knows their basic shapes.