This week’s image from the Hubble Space Telescope is striking: The beautiful galaxy NCG 1097, as captured using two of Hubble’s instruments working in tandem. This barred spiral galaxy is located 48 million light-years away, in the constellation of Fornax, and has a twisted shape caused by gravitational interactions with a nearby companion galaxy called NCG 1097A.
This particular galaxy is known for being the site of no less than three supernovas over the past two decades, with stars exploding in epic events when they reached the ends of their lives. The supernovas were called SN 1992bd, SN 1999eu, and SN 2003B, named for the years of their observations.
This image of NGC 1097 was taken using two of Hubble’s instruments, the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS). To create this one image, both instruments were used to observe the same target, then data from both were combined to create the image.
“The idea that two different cameras can take a single image is not very intuitive,” Hubble scientists explain. “However, it makes far more sense after delving into how beautiful astronomical images like this are composed. Our eyes can detect light waves at optical wavelengths between roughly 380 and 750 nanometers, using three types of receptors, each of which is sensitive to just a slice of that range. Our brain interprets these specific wavelengths as colors. By contrast, a telescope camera like the WFC3 or ACS is sensitive to a single, broad range of wavelengths to maximize the amount of light collected. Raw images from telescopes are always in grayscale, only showing the amount of the light captured across all those wavelengths.”
Both the WFC3 and ACS were used to image in the galaxy in particular wavelengths, as controlled using filters. Each filter is used to look at a specific wavelength corresponding to a certain color and produces a greyscale image. Then a total of seven of these filtered images were combined to produce the image as seen above.
