Space Place Activity: Light and Color
Topic/Concept: Boys and Girls Club: Light, Color, and the
Temperature of Astronomical Objects
Type of Activity: 20 min. activity for small group (3-4 kids),
teacher interaction required
Prerequisite knowledge required: none
Resources required: color images of astronomical objects,
rheostat, diffraction gratings
Learning Objectives: (1) understand the range of temperatures of
objects in space, why some objects (stars) are hot while others (planets,
comets) are cold, and what determines the relative temperature of
astronomical objects. (2) realize that the temperature of a star changes
the type of light it gives off, and that hotter stars are bluer; colder
stars are redder. (3) talk about other types of light that different
objects can give off (like infrared).
Common misconceptions: Many kids associate “red” with “hot” and “blue”
with “cold,” and this can be hard to reverse.
Detailed description of activity: (1) We had the group sort
through the images and arrange them in piles of things they thought were
“hot” and things they thought were “cold.” The images were: a blue star,
a red star, a yellow star, an AGN with a bright accretion disk (artist
rendition), the moon, mars, venus, and an asteroid. Typically the
students put stars in the hot pile, planets in cold pile, although
sometimes they recognized venus and said it was hot, and the galaxy
usually brought up questions about what it was, and why a black hole could
make something very hot. Key discussion points were that stars make their
own energy/heat, and in general a planet further from the sun is colder.
(2) We then asked them which star they thought was hottest—the red one,
the yellow one, or the blue one. We used the rheostat and the diffraction
gratings to show that at low voltage/temp, the rheostat gave off
red/orange light, and when we made it hotter it gave off more yellow, than
more blue light. We discussed what this meant for which star was hottest.
(3) We organized the pictures in order from hottest to coldest, and told
them the actual temperature of the objects (in degrees F, since this is
the scale most relevant to them). (4) If there is time and students are
grasping the concepts so far, you can talk about what kind of light a
colder or hotter object might give off, and what kind of light a human
emits.
Assessment: judging understanding through discussion and teacher
questions to students.
Comments: this activity was conducted with 3 groups of 2-4
students, with varying results. Older (10+ yrs) seemed the most
successful at grasping the concepts. Adaptations may be needed for
younger kids.