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Video: Zoom into the Dumbbell Nebula



Credit
: NASA and L. Barranger (STScI/AVL)

Imaging the Dumbbell Nebula:
Different results from different techniques
By Zolt Levay (Hubble Heritage/STScI)

KPNO EktachromeVLTWIYN InfraredWIYN WIYNHST

These images look surprisingly different. At first, they look different mostly in the their color. Looking a bit more closely, you might see differences in the structure of the nebula and in the level of detail. The images are different because they were made using various telescopes, cameras, filters and imaging technology. One of them was made using color photographic film (Kodak Ektachrome), the others were produced from digital images recorded using electronic detectors (CCDs). The digital color images were reconstructed from separate black and white images made through different color filters (more details about this). The images shown here are all at the same scale and orientation. Some of them do not show as much of the nebula as others because the telescope and cameras see different amounts of the sky.

Even images made using the same telescope can be wildly different. Most of the differences come about because different filters were used to produce each image, selecting different colors in the light from the nebula. Some filters isolate light in a very small range of colors (narrow wavelength band) from specific chemical elements (hydrogen or sulfur, for example). Other filters sample a broader range of colors (broad wavelength band). In reconstructing a color image, the exposures from each filter were assigned color in various ways. In some cases, the images show light that we cannot see with our eyes. Infrared light is redder than the reddest light we can see, but instruments can record this light.

This table shows more details for each image:

Image Telescope Filters, Colors
KPNO 4m Kodak Ektachrome color film
VLT 8.2m
Ha 656nm 
Red
[O III] 501nm 
Green
B 429nm 
Blue
WIYN 3.5m
1.02mm (IR) 
Red
[S III] 953nm 
Green
Ha 656nm 
Blue
WIYN 3.5m
Ha 656nm 
Red
[O III] 501nm 
Green
[O II] 373nm 
Blue
WIYN 3.5m
Ha 656nm 
Red
[O III] 501nm 
Green
O I 630nm 
Blue

HST WFPC2
[S II] 673nm 
[N II] 658nm 
Red
Ha 656nm 
Green
[O III] 501nm 
Blue