Astronomical Imaging: Do You See What I See? Using Filters to View Astronomical Pictures

Why use filters?

Materials A set of colored pencils, crayons or markers 3 pieces of cellophane: red, blue, yellow A color printout of the Crab Nebula image Worksheet Viewing the Crab Nebula with Filters The gas is several different colors because it is at different temperatures. The hottest part is blue in color, the coldest is red. We are going to look at the Crab Nebula through our filters (pieces of colored cellophane).

Filtering Activity Procedure 1.Within your team assign one filter/color of cellophane to each team member. Someone will be blue, someone will be red and the other person will be yellow. 2.Hold your filter/piece of cellophane over the image of the Crab Nebula. Quickly sketch what you see. Do not remove the filter while you are sketching. Try to make your sketch as accurate as you can in color, size and detail. Your partners should do the same thing with their assigned cellophane color. 3.Once everyone on your team has finished making a sketch of the Crab Nebula compare your sketches with one another. Are they all the same? Are they different? If they are different, discuss the ways in which they differ.

Follow up Discussion to Filtering Activity We could have placed our cellophane filters into a holder and made a color filter wheel like this so that only one filter (color) was visible at a time.

Why do Scientists Use Filters?

Looking at the Sun through filters

Viewing astronomical objects in different wavelengths Now we are going to view some astronomical objects in not just different visible wavelengths of light but different wavelengths of the EM spectrum, such as infrared and x-ray. Just as viewing through different colored filters allowed us to focus on different aspects of a photograph, using different wavelengths of the EM spectrum gives us more detailed information than we would get from just one part of the spectrum. Radio images highlight the presence of cooler gas clouds (especially hydrogen) and solar flares and sunspots Infrared (IR) images show areas of low-energy heat and can see through clouds of gas and dust. IR is used to observe areas of star formation and nebulae. Visible light images depict primarily gases and dust X-ray images reveal high-energy heat emissions from supernovae and black holes

TD: Astronomical Images in Different Wavelengths Let’s start our exploration by viewing the Crab Nebula in more wavelengths than just visible light:

Adaptive Optics Adaptive optics fixes the blurring of deep-space images by correcting for the turbulence in Earth’s atmosphere. Light is bounced off a deformable mirror that smooths out the image. This process repeats every millisecond. With this new technology, ground-based telescopes can take pictures with the clarity of the Hubble Telescope. TD: DETWINKLING THE STARS Scientists are extending adaptive optics to biology and microscopic views inside of cells