The Hubble Space Telescope captured an incredible photo of a spiral galaxy shaped like an eye using its high-resolution camera. Two Hubble instruments were used to capture the photo: the Wide Field Camera 3(WFC3), and the Advanced Camera for Surveys (3ACS).

This detail photo shows NGC 1097’s heart. It is described by NASA as a barred spiral galaxie that lies 48 million light years from Earth in the constellation Fornax. This photo shows the intricate web of stars and dust at NGC 1097’s centre. Long tendrils of dust radiating outward are what give the red hue.

Two instruments make a photo

Two Hubble instruments were used to create the photo: the Wide Field Camera 3(WFC3), and the Advanced Camera for Surveys (3ACS). NASA states that although the idea of two cameras being able to capture a single image may not be intuitive, it is essential to create photos like this.

The European Space Agency (ESA), explains that “our eyes can detect light waves between approximately 380 and 750 Nanometers using three types of receivers, each one sensitive to just a small portion of that range.”

These wavelengths are interpreted by the brain as colors. A telescope camera such as the WFC3 and ACS, on the other hand, is sensitive to a wide range of wavelengths in order to maximize light collection. Raw images taken by telescopes are always in grayscale and only show the amount of light captured across all wavelengths.

the heart of NGC 1097 as captured by Hubble

NASA explained that these color photos are made with filters. This subject is also covered in detail on the Hubble website.

The ESA continues: “By sliding an aperture over the WFC3 and ACS instruments, only light within a very narrow wavelength range can pass through.”

“This image uses a filter for green light at 555 nanometers. This produces a grayscale image that shows only the wavelength of the light. Astronomers can then add color to the image. The multicolor image of NGC1097 is made up of seven images that were processed with seven different filters.

20 years of photography

Recently, the ACS celebrated 20 years of continuous use. It has taken over 125,000 photos over that time and whose observations have led to many discoveries.