Galaxy’s Stunning Transformation by Hubble Filters

The barred spiral galaxy NGC 1385 appears in two strikingly different Hubble Telescope images, attributed to the use of different specialized filters.

This luminous tangle of stars and dust is the barred spiral galaxy NGC 1385, located about 30 million light-years from Earth. The same galaxy was the subject of another Hubble image of the week (see image below), but the two images are noticeably different. This more recent image has many more pinkish red and umber tones, while the previous image was dominated by cool blues. This chromatic variation is not only a creative choice, but also a technical one, made to reflect the different number and type of filters used to collect the data used to create the respective images.

Hubble Space Telescope image of spiral galaxy NGC 1385, located 68 million light-years from Earth, in the constellation Fornax. Credit: ESA/Hubble & NASA, J. Lee and the PHANGS-HST team

Understanding telescope imaging techniques

It’s understandable to be somewhat confused as to how the same galaxy, imaged twice through the same telescope, can appear so differently in two different images.

The reason is that Hubble – like all powerful telescopes used by professional astronomers for scientific research – is equipped with a series of filters. These highly specialized components bear little resemblance to filters used on social media: These software-driven filters are added after the image is created and cause information to be lost from the image as certain colors are exaggerated or reduced for aesthetic effect.

Telescope filters, on the other hand, are pieces of physical hardware that allow only very specific wavelengths of light to enter the telescope while the data is being collected. This does cause light to be lost, but it does mean that astronomers can investigate extremely specific parts of the electromagnetic spectrum. This is very useful for a number of reasons; For example, physical processes within certain elements emit light at very specific wavelengths, and filters can be optimized for these wavelengths.

Compare images of NGC 1385

Check out this week’s image and the previous image of NGC 1385. What are the differences? Do you see the extra details (resulting from using additional filters) in this week’s image?