One of the most beautiful sights in the night sky are the innumerable twinkling stars. They make-up the constellations, create the “milk” in the Milky Way, and for centuries were used as navigation tools for Earth’s explorers. Stars spark the imaginations of artists and scientists alike. In this Lesson Plan, you will have the opportunity to learn the basic science behind these wondrous objects!
Lesson 1: Common questions about Stars
Where do these points of light come from? Great question! Stars are born in dense regions of hot gas throughout the galaxy. These “stellar nurseries” are where the materials that form stars congregate.
How do they form? Stars form when gases gather under the force of gravity. Accumulated and dense gases begin their lives as protostars – baby-stars born in stellar nurseries. See this NASA image for an example of a young “protostar.”
How do they shine and why do they twinkle? Aren't stars amazing to look at? Stars shine for the same reason our Sun does. Stars “burn” hydrogen and helium in their deep interiors, converting mass into energy based on Einstein’s famous equation E = mc2. However, most stars don’t actually twinkle. The twinkling effect comes from dust in the atmosphere or other particles in the interstellar medium. They just appears to twinkle to the human eye.
Why do scientists study stars? Stars contain valuable information about the physics of the Universe. For example, they teach us about the processes behind nuclear reactions. They record history and through them, scientists can peer into the deep past of the Universe. Stars also harbor potential planetary systems. Some of those planets may be rocky and Earth-like, and potentially contain life!
Why are stars important? Stars are the crucibles of heavy metals. Massive stars are where elements important to living organisms are forged. See this NASA image for a beautiful quote by the astronomer Carl Sagan on this subject.
If starts are born do they also die? Yes, stars don’t live forever. As they age, they become hotter and hotter. Eventually, they implode as spectacular planetary nebulas, supernovas, and supernova remnants. See the NASA image for a beautiful display of a supernova remnant.
Are stars all the same or are there different types of stars? Stars are not all the same. The nearest star to us, the Sun, is but one type of the many types of stars in the universe. The stars we see in the night sky range from smaller dwarf stars (like our Sun) to red giant stars that are 30-100 times the size of the Sun. See this UniverseToday image for a summary of different star types, and their size comparisons. Our sun is quite small compared to many other stars we can see in the night sky! The evolution (change with time) of stars are stories of life, death, and rebirth. See this NASA image for a beautiful pictorial summary.
Activity 1: Stargazing
Everyone should do a little star gazing once in a while! It is a beautiful thing to do. Take some time to look up at the night sky and try to answer the following questions:
Can you name the objects you can see?
What do they look like?
And what are they doing?
Are the objects interacting with one another? If so, how?
After observing and reflecting, document what you discover in words and sketches. This is an important first step in the scientific method. As you document and sketch, think about the following questions:
Does the pattern of stars you see CHANGE over time?
Do you have some ideas or explanations for these changes? In other words, why do the stars seem to move as time passes?
To the best of your ability, illustrate how the objects you’re observing move across your night sky.
For an introduction to observing the night sky, see this online Crash Course; useful for both students and instructors, and see this link for a more detailed discussion of this exercise and its relation to the broader scientific method.
Identifying Star Types: You can attempt to identify different types of stars with the naked eye (or with the help of a telescope if you have access to one) Scientists use the Hertzsprung-Russell Diagram to identity stars. Using this diagram can guess at the star type just by it's brightness and color?
The night sky look different depending on where you are standing on Earth. For example, the Northern Hemisphere contains different starts and constellations than the Southern Hemisphere.
This link is an excellent resource to see how the night sky changes based on your location and time you are looking. Pick a constellation and record how it changes when you vary location and time.
If you’d like to go beyond observing skies with your eyes, you can follow the guide to astrophotography to take some pictures of the night sky. Here is a more professional version. If you get some good photos, tweet your results to the Sky Day Project. Have fun!
This educational guide was written by Howard Chen. Howard is currently a graduate student in the Earth and Planetary sciences Department at Northwestern University.