Handbook of Nature-Study · Lesson CCXXIX · Topic 37: The stars
229. The two Dog Stars
Goal: Your child can find Sirius from Orion's belt, find Procyon, and knows Sirius is the brightest star in the night sky.
You'll need
- A clear winter evening
- A red-covered flashlight
- A nature notebook and a pencil (colored pencils if you have them)
What's in the book
The lesson has a leading thought, a method showing how to find Sirius along Orion's belt and Procyon to make a kite shape, and six observations about the two Dog Stars.
The lesson, step by step
When and where
Clear evenings from January to March, after Orion is well up, about 8 or 9 p.m. Face south and southeast. Stargaze with an adult, in a dark spot away from roads, such as a back yard or a field you have permission to use. Dress warmly, bring a blanket, and cover a flashlight with red cellophane or a red balloon so your eyes stay used to the dark.
The leading thought
The Great Dog Star, Sirius, is the most famous of all stars in the literature of the ages. The Two Dog Stars were supposed by the ancients to be following the great hunter, Orion.
Find Sirius
a straight line drawn through Orion's belt and dropping down toward the eastern horizon ends in a beautiful white star, which is Sirius.
How do you find Sirius? Which rises first, Orion or Sirius?
Find Procyon
Follow the book: draw a line from Betelgeuse to Rigel, from Rigel to Sirius, and then complete a kite shape. The fourth corner is Procyon, the Little Dog Star.
Which is the brighter, the Great Dog Star or the Little Dog Star? Can you see any fainter star near Procyon?
Twinkle
Watch Sirius low in the sky. It often flashes many colors. Ask: Is the star changing, or is something between us and the star? (The air, which bends its light this way and that.)
What we know now
The book asks what Sirius's color tells about its stage of life. Today we know its white color means it is hotter than our Sun. Sirius is about twice as heavy as the Sun, gives about 25 times as much light, and is one of our nearest neighbors, about 8.6 light-years away. That nearness is why it is the brightest star in our night sky.
Nature notebook
Make a chart showing Orion and the two Dog Stars.
Answers to the book's problems
Orion rises first; Sirius follows, like a dog after the hunter. Sirius is brighter than Procyon. Procyon is nearer to the North Star than Sirius. Procyon has a fainter star near it (the book calls it a twin).
Worked out for this site from the scan. If a number in your copy differs, trust the book.