Overview: Students combine work they've done on Orion to showcase what they know about how color is used in astronomy, as well as interpreting flux and luminosity.
Electronic Resources: Sunflower filtered images (Flower1.fits (FITS), Flower2.fits (FITS), Flower3.fits (FITS), Orion Chandra image (X-ray): (OBSID 3744, available through the ds9 Virtual Observatory, Process: How to open a certain OBSID), Orion filtered images from Hubble Space Telescope (visible light) (m42r.fits (FITS), m42g.fits (FITS), m42b.fits (FITS)) Orion "unfiltered" black and white image (visible light): (m42_combined_wcs.fits) (FITS) Note: this image was created by combining the three filtered images above, and scaling to a range of pixel values 0-255. It is technically not "unfiltered" but does represent the overall 'unfiltered' intensity.
Instructor assigns the following tasks:
- Students create three pairs of images:
- A true color and false color image of the sunflower in visible light
- A true color and false color image of the Orion nebula in visible light, matched by WCS coordinates
- A true-color and false color image of the Orion nebula in X-ray light, matched by WCS coordinates
- For each image, write a paragraph describing how it was created (method), what color represents (i.e. flux or energy) and simple observations about flux, angular size, positions, shapes and textures.
- Students choose 2 objects in the X-ray image of the Orion nebula (or the same object to compare between the visible and X-ray image), and observe the color and flux received from each object.
- Focus question: Why might these objects appear different? Develop a model (explanation) for why.
- Students publicly record their questions about the Orion nebula as seeds for possible research projects related to young, active stars.
- Students should use the work they have done previously on the Orion nebula, so this task should focus more on developing good written descriptions of the method, and answering the focus question.
- Example of WCS coordinate-matched true color images: Visible light from Hubble on left, X-ray light from Chandra on right.
- Focus question notes:
- Possible models for differences in stars are they are different distances and/or luminosity, and possibly different temperatures, although students should wonder more about what color indicates—getting them primed for the next investigation.
- If students have trouble with the question, ask "From which star do we receive higher flux? Which star has a higher luminosity?" This can lead to a discussion of distance effects on flux.
- Possible extensions / alternatives: Students develop a model for why the visible light image looks different from the X-ray light image, instead of focusing on why 2 X-ray objects look different. (This would focus them more on the presence of dust/gas, and the model may be that X-rays "punch through the gas, and/or the gas does not emit much X-ray light.)
- Examples of student comparisons and written descriptions: David's Project (PDF)
- Examples of student models for a more general question "Develop a model and diagram for why the Orion nebula looks this way in these images? What objects give off what kinds of light?"