Sun, Moon, and Stars: Astronomy for Beginners · Part III, Ch. IV · Part 3: Part III: The stars
28. Groups and clusters of suns, and the nebulae
Goal: Your child can tell the difference between a star cluster and a nebula, and knows that some 'nebulae' turned out to be whole galaxies.
You'll need
- The book, open to Part III, Chapter IV
- Binoculars (optional)
- Black paper and a white crayon or chalk
What's in the book
The chapter introduces the Milky Way, then star clusters (often round, with thousands of suns), and nebulae, from the Latin for 'cloud': some turn out to be distant star clusters, others glowing gas. It describes the great nebula in Orion, the nebula in Andromeda, and the Magellanic Clouds, and leaves open whether some of them are other 'universes' far beyond our own.
The lesson, step by step
Read together
Read the chapter aloud.
The word "nebula" comes from the Latin word for "cloud," and the nebulae are so named from their hazy and cloud-like appearance.
A world with no night
Read the book's picture of a planet inside a star cluster, where there would be no night. Ask: Would you like to live there? What would you miss?
The open question, answered
The book says it is an open question whether some clusters and nebulae are separate 'universes' far outside our own. Say: About thirty years after this book, astronomers answered it.
What we know now
In the 1920s, Edwin Hubble showed that the Andromeda 'nebula' is a whole separate galaxy, about 2.5 million light-years away, with hundreds of billions of stars. There are billions of galaxies beyond our own.
The round globular clusters belong to our own Milky Way. The Magellanic Clouds are two small neighbor galaxies.
The Orion Nebula is a vast cloud of gas and dust where new stars are being born, about 1,300 light-years away. The 'one other gas, the nature of which we do not know' turned out to be oxygen, glowing in an unusual way.
Draw a cluster and a nebula
On black paper, draw a globular cluster: many dots crowded at the center, thinning at the edges, as the book describes. Beside it draw a soft, smudgy nebula with a few stars inside, like Orion's.
Tell it back
Ask your child to explain what a nebula is, and what we now know about the Andromeda nebula.
Check questions
What is the most common shape of a star cluster?
Where in Orion is the great nebula?
About how big does the book say the Great Magellanic Cloud looks, compared with the full moon?
Notice it this week
In winter, look at the middle 'star' of Orion's sword (below the belt). The book says it looks slightly misty. With binoculars the mist is easy to see. In autumn, from a dark place, the Andromeda Galaxy is a faint smudge you can see with your bare eyes or binoculars: light that left it about two and a half million years ago.
Answers to the book's problems
Round (globular). The middle star of Orion's sword-handle. About two hundred times the size of the full moon.
Worked out for this site from the scan. If a number in your copy differs, trust the book.