Sun, Moon, and Stars: Astronomy for Beginners · Part II, Ch. II · Part 2: Part II: A closer look at the Solar System
14. More about the Sun: sunspots and eclipses
Goal: Your child can describe the parts of a sunspot and the eleven-year sunspot cycle, and can explain total, partial and annular eclipses of the Sun with a ball and a lamp.
You'll need
- The book, open to Part II, Chapter II
- A lamp with the shade off, and a small ball
- A coin
- For safe Sun-viewing: a kitchen colander or a pinhole card, and a sheet of white paper
- A compass (the kind with a needle)
What's in the book
This chapter looks closer at sunspots (umbra, penumbra and nucleus), their changes, the eleven-year sunspot cycle and its link with compass needles, and the 'willow-leaf' mottling on the Sun. Then it explains eclipses of the Sun, with a candle and a ball, and quotes an eyewitness of the total eclipse of 1860 in Spain.
The lesson, step by step
Safety first
Safety first: never look at the Sun, not even for a moment, and not through sunglasses, smoked or darkened glass, film, binoculars or a telescope. It can hurt your eyes for good, and it does not hurt while it happens.
SayEven during an eclipse, when part of the Sun is covered, the uncovered part can still hurt your eyes. We will watch eclipses only by projection.
Read together
Read the chapter aloud. Stop after the sunspot cycle and ask: Why do you think people laughed at the man who compared the sunspots and the compass needles? Were they right to laugh?
The eleven-year beat
SaySunspots come and go in a rhythm, many for a few years, then few, then many again, about every eleven years. And when there are most spots, compass needles on Earth shake most.
Look at your compass needle. It points north, steady, because the Earth is a giant magnet.
Small covers big, and making an eclipse
Hold a coin at arm's length and close one eye. Cover a whole house, tree or car far away with it.
Any small object very near will easily hide from your sight a large object at a considerable distance.
In a darkened room, stand facing the lamp, a few feet away. Move the ball slowly across, between your eye and the bulb. When it covers the bulb exactly, that is a total eclipse. A little high or low, a partial one. Move the ball farther from your eye so it looks smaller than the bulb: a ring of light shows all round. That is an annular eclipse.
Never do this with the real Sun.
What we know now
Sunspots are not cyclones or holes. They are patches where the Sun's magnetism is very strong. They look dark only because they are a few thousand degrees cooler than the glowing surface around them.
The bright outburst the two astronomers saw (in 1859) was a solar flare. Flares and eruptions can fling particles toward Earth that shake compass needles, make bright auroras (northern lights), and even upset satellites and power lines.
The 'willow leaves' are called granules: the tops of bubbling columns of hot gas, each several hundred miles across, rising and sinking in minutes.
Tell it back
Ask your child to retell the 1860 eclipse from the book: the colors of the sky, the people, the birds and the flowers.
Check questions
Why can an eclipse of the Sun happen only at new moon?
What is an annular eclipse?
How long is the sunspot cycle?
Notice it this week
On a sunny day, hold a colander over white paper with your back to the Sun. Each hole makes a little round picture of the Sun. During a partial eclipse they all turn into little crescents. Look up the date of the next solar eclipse visible where you live.
Afterwards
Each sunny day this week, check a NASA solar-observatory image of the Sun online with an adult and count the spots. Does the count change?
Tip
If an eclipse comes your way, the colander or a pinhole card, or the dappled light under a leafy tree, is the safest way for children to enjoy it.
Answers to the book's problems
Because only at new moon is the Moon between the Earth and the Sun. An annular eclipse is when the Moon is a little farther away, looks slightly smaller than the Sun, and leaves a bright ring showing round it. About eleven years.
Worked out for this site from the scan. If a number in your copy differs, trust the book.