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What Determines a Star's Color?

Using Slooh’s Online Telescope and integrated NGSS aligned Quest learning activities, you can capture your own images of stars and learn about the relationships between each star's characteristics. Star Light, Star Bright is one of 60+ curriculum-aligned STEM Quest learning activities on Slooh for students 4th grade to college.

Slooh’s Online Telescope:

If you are an educator looking for fun, interactive ways to teach NGSS: 5-ESS1-1, as well as other standard curriculum codes related to astronomy, keep reading to the end for more information on the Stars Light, Star Bright Quest and ways to easily integrate Slooh into your classroom.


What Determines a Star's Color?

Have you ever noticed how metal glows when it heats up? That glowing is the thermal energy of the metal being converted into electromagnetic energy, also known as light! Every object with a temperature, including us, gives off a spread of electromagnetic energy, which human eyes then translate into color. This phenomenon is called blackbody radiation, and it is the reason stars appear the colors they do.

Although stars emit light at a large variety of frequencies, they emit more of a certain frequency depending on their temperature. Hot stars give off mainly blue light, while cooler stars appear red. When stars emit an equal amount of red and blue light, they appear white! To the naked eye, most stars may seem to be white, but we can see their true colors through telescopes. Astronomers differentiate between stellar colors and temperatures by classifying each star based on its spectral type. Check out the diagram below to see how a star’s color correlates with its temperature and spectral type.

Within the spectral types, the subtypes allow you to narrow down a star's temperature. In each type, 0 stars are the hottest of that class, and 9 stars are the coolest. The Sun’s temperature is around 5,800 Kelvin, making it a G2 (yellow) star. Stars go through a life cycle during which their sizes, temperatures, and colors can change. For example, the Sun will eventually expand and become a red giant star!

Where To Put a Star's Thermometer

Now that you know that a star’s color is based on its temperature, how is that temperature determined? Check out the diagram below to see the layers of the Sun. Each layer is at a different temperature, with it being hottest at the core and cooling as you move towards the outer layers. The temperature reported for a star is the temperature of the stellar photosphere, the star’s surface. The starlight we see from the Sun and other stars is emitted from the photosphere, which is why we use its temperature to determine the color of a star.


More About Slooh's Star Light, Star Bright Quest

In this quest, you will use Slooh’s telescopes to capture images of one particular type of celestial object: Stars! You will analyze your captured images to determine why some stars appear brighter than others. Once you've gathered your data, you will learn more about the main stellar properties.

Related Slooh Quests

  1. Light: The Language of Astronomy

  2. Our Radiant Star

  3. There Goes the Sun

More About Slooh’s Astronomy NGSS Aligned Learning Activities

Slooh’s Online Telescope is a learning platform designed to support any educator in teaching astronomy to meet NGSS requirements by collecting and analyzing real-world phenomena. No previous experience with telescopes is necessary to quickly learn how to use Slooh to explore space with your students.

You can join today to access Slooh's Online Telescope and all 60+ Quest learning activities if you are able to make astronomy a core subject of study for the semester or year. If you only have a few weeks to study astronomy, we also have a curriculum designed to fit your busy academic schedule and budgetary limitations. To learn more about our offers, click here.

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