Welcome to http://www.handsonuniverse.org/activities/Explorations/StarColor/
Goal: Figure out the colors and temperatures of stars!
Procedure: Measure and compare star brightness counts in images taken with red green and blue filters.
- HOU image processing software.
- HOU teachers and museum or community center partners may download the images for the mystery star and for M42 in .fts format.
Images Taken with Filters
The HOU images used for these activities were taken in sets of three. For each set, images were taken with a red, green and then a blue filter on the telescope.
Why Use Filters?
The purpose of using filters is to be able to compare the amount of starlight which passes through each filter. By comparing the amount of starlight getting through each color filter, astronomers analyze the color of the light coming from the stars.
Star Color and Temperature
All stars are very hot! However, some stars are cooler or hotter than other stars. Cooler stars shine with more light in the yellow-orange-red areas of the spectrum. Hotter stars shine in the bluish areas of the spectrum.
Activity A: Color of Mystery Star. You will compare three images of a mystery star. Each image was taken with a different color filter. You will compare the brightness of the mystery star in each of the three images. The star will look brightest in the image which was taken with a filter that is most like the color of the light coming from that star. Does the mystery star shine with more red light or more blue light? Is this mystery star a cooler star or a hotter star?
Activity B: Color of Stars of M42. You will compare three images of the stars of the Orion Nebula, M42. Each image was taken with a different color filter. You will compare the brightness of a star in each of the three images. The star will look brightest in the image which was taken with a filter that is most like the color of the light coming from that star. Are the stars of the M42 more reddish or more bluish? Are these cooler stars or hotter stars?
Activity A: Color of Mystery Star
Mystery Star.... Does This Star Shine with More Red or More Blue Light?
Open the image, mysred.fts [mystery star image taken with a (red) filter]. You will repeat this process for mysgreen.fts (green filter) and mysblue.fts (blue filter).
Color the image. Even though a color filter was used on the telescope, the image still appears in shades of grey. You can use the color palette to help you remember which filter was used when the image was taken at the telescope.
Measure the brightness counts of the mystery star.
Image and Filter
red filter: mysred.fts
green filter: mysgreen.fts
blue filter: mysblue.fts
Compare the brightness counts in the three filters.
Activity B: Color of Stars of M42
Bright Stars in the Orion Nebula.... Are They More Red Or More Blue?
In the constellation, Orion, there is a region called the Orion Nebula. A nebula is a fuzzy patch of sky as seen with your eyes or a telescope. The Orion Nebula is a very huge dust and gas cloud in space with lots of stars inside. In fact, in nebulas like Orion, the dust and gas collapses to make new stars. The Orion Nebula has a lot of new, young stars.
When astronomers look at the Orion Nebula (Messier object number 42 or M42) with telescopes, four bright stars appear in the center of the nebula. These stars are called the Trapezium because there are four.
Open the image, M42red.fts [M42 image taken with a (red) filter]. You will repeat this process for M42green.fts (green filter) and M42blue.fts (blue filter).
Log scale the color palette in order to see the dimmer parts of the image.
Match the image orientation to the photo.
Color the image because even though a color filter was used on the telescope, the image still appears in shades of grey. You can use the color palette to help you remember which filter was used when the image was taken at the telescope.
Measure the brightness counts of the brightest star in the Trapezium.
Image and Filter
Brightest Star of the Trapezium
For the brightest star of the Trapezium, compare the brightness counts in the three filters.
The color of stars reveal their temperature. Cooler stars shine with more red light. Hotter stars shine with more blue light.
Download the .fts images of the mystery star and M42.
* HOU Explorations *