On July 6th, 2012, the Public Observatory was packed with visitors observing Venus and the Sun. Throughout the day, astronomy educators captured three different views of the Sun. This collection shows one picture in white light, one in violet, and one in red. Each of these colors allows you to see a different layer on our closest star.
Dramatic sunspots on the Sun’s surface are clearly seen in the white-light image, taken at 3:25 pm. Bright streaks near the edge of the Sun are faculae, or hot clouds close to the Sun’s surface. Sunlight contains all the colors of the rainbow, but the combination of those colors is warm, yellowish white, the natural color of sunlight. A gray (neutral density) filter was used to reduce the sunlight to safe levels.
The violet image was taken with a Calcium-K filter at 11:46 am. Only the wavelength of light that corresponds to the Calcium II K transition is collected by this telescope. All of the other colors (red, green, etc.) were filtered out. Scientists use this wavelength to get a good indicator of the amount of magnetic activity on our Sun as well as other stars. Regions of high magnetic activity like sunspots appear dark. Scientists measure the brightness of stars in Calcium K and use this information to gauge the relative ages of stars.
The red image was taken at 1:53 pm with a Hydrogen-alpha filter. Again, this refers to a specific wavelength of light. In this image, the green, blue, and violet light are filtered out, while only the red light corresponding to Hydrogen-alpha is allowed through the filter. Sunspots are dark, while the hot clouds that surround them (called plages) are brighter yellow.
Compare the features on these images to see how different filters affect your view of the Sun! Sunspot 1515, to lower right, was especially active on June 6. The sunspot region unleashed an X-class solar flare (the strongest category of flare) just a few hours after these photographs were taken. Close-ups of this region are shown in small panels to the right.
Camera: Lumenera SKYnyx2-2M
Tele Vue-85 with AstroSolar ND5 film solar filter
Lunt 60mm Calcium-K telescope
Lunt 100mm Hydrogen-alpha
Image Number: WEB12518-2012
Credit: Photo by Geneviève de Messières and Emily Berkson, Smithsonian Public Observatory Project
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