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Imaging Through Filters

filter set & hot spring link to Bonnie Sue's Photography Gallery link to Bonnie Sue's Photography Gallery The Hubble Heritage image of NGC 3132 was constructed from black-and-white Hubble Space Telescope data obtained from the public archive. The original observers used 5 different filters to select wavelengths of light corresponding to 5 different chemical elements which are each sensitive to different physical conditions within the nebula. Hence the 5 greyscale images displayed on the left appear somewhat different from each other. The Heritage Team assigned the primary colors of light to 3 of these images in order to construct the glowing image highlighted as our November 1998 release. In this case, color corresponds to excitation energy, which depends on the temperature of the gas and the amount of ultraviolet light from the hot star in the center.

A different combination of 3 filters was used to construct the images on the collage page, which thus appear different from our final color image. Can you tell which ones they were?

Nature displays a remarkable economy of form as displayed on the left by the striking similarity of Yellowstone's Grand Prismatic Spring to the Hubble Heritage project's new rendering of NGC 3132. Though the two physical systems are completely different, the reasons for the similarity of the images do share some common threads. In the Grand Prismatic Spring the colors are produced by different species of thermophilic bacteria that live in narrow temperature ranges as the waters of the hot spring naturally cool farther from the source of the heated water. The reddish bacteria at the outer edge survive in the coolest water with the yellowish and greenish bacteria living in progressively hotter water. The water in the central blue area of the spring is too hot to support any of the bacterial species.

The colors on the Heritage image of NGC 3132 are similarly derived with different colors tracing three different atomic species in the planetary nebula. The reddish colors show areas where singly ionized nitrogen emits, green maps out areas where the H-alpha emission from hydrogen occurs (yellow regions have both [N II] and H-alpha), and blue traces emission from doubly ionized oxygen, [O III]. The segregation of these species occurs because each atomic species requires different levels of ionizing radiation which decreases with distance from the central star.

Image of Yellowstone Grand Prismatic Spring copyright Bonnie Sue Photography.