Sun, Moon, and Stars: Astronomy for Beginners · Part III, Ch. I · Part 3: Part III: The stars
25. Many suns
Goal: Your child can explain why stars look like points of light even in a telescope, and that stars differ in size, color and brightness.
You'll need
- The book, open to Part III, Chapter I
- A flashlight
- A long hallway, yard or street (with an adult) at dusk
What's in the book
Part III leaves the Solar System for the stars. The first chapter reminds us that the Sun is just one star and every star a sun, explains why no telescope shows a star as a disc, and says that stars are not all alike: the book sorts them into white suns, golden suns like ours, variable stars and small red suns. It ends by saying that every star is moving.
The lesson, step by step
Read together
Read the chapter aloud.
For the sun is a star — only a star.
Bright because near, or near because bright?
At dusk, have one person stand close with a flashlight and another far away with the same kind of flashlight. Which looks brighter? Then switch one flashlight for a dimmer one (or cover it with a tissue) and put it close. Can you still tell which is nearer just by brightness?
SayThat is the book's puzzle. A star may look bright because it is near, or because it is big, or because it is very brilliant. We can't tell from brightness alone.
Stars have colors
Read the four kinds of suns. On a clear night, compare a few bright stars: some look white or bluish, some yellow, some orange or reddish. In winter, Betelgeuse (orange-red) and Rigel (blue-white) in Orion are a good pair.
What we know now
Star colors tell their temperature: blue-white stars are the hottest, yellow ones like our Sun are in the middle, and red ones are the coolest.
The book is right that small red suns are hard to see. In fact, small dim red stars are the most common kind of all.
Telescopes can now measure the size of some nearby giant stars directly. Betelgeuse is so big that, put in place of our Sun, it would swallow the orbits of Mercury, Venus, Earth and Mars.
Our Sun is an ordinary, middle-sized star, as the book suggests.
Tell it back
Ask your child to explain why stars all look like tiny points, while planets show a small round disc in a telescope.
Check questions
How long does light take to reach us from the nearest known star, according to the book?
Into what four classes does the book sort the stars?
Does the brightest star always have to be the nearest?
Notice it this week
Find three stars of different colors and write their colors in your star notebook. A free sky app can tell you their names.
Answers to the book's problems
Four years and one-third (or four years and four months). White suns, golden suns, variable stars, and small red suns. No: a star may look bright because it is very large or very brilliant, even if it is farther away.
Worked out for this site from the scan. If a number in your copy differs, trust the book.