Against an inky black background, the blue swirls of spiral galaxy NGC 6956 stand out radiantly. NGC 6956 is a barred spiral galaxy, a common type of spiral galaxy with a bar-shaped star structure at its center. This galaxy exists 214 million light-years away in the constellation Delphinus.

Scientists used NASA’s Hubble Space Telescope to image NGC 6956 to study its Cepheid variable stars, which are stars that brighten and dim at regular periods.

Since the period of Cepheid variable stars is a function of their brightness, scientists can measure how bright these stars appear from Earth and compare that to their actual brightness to calculate their distance. As a result, these stars are extremely useful in determining the distance of cosmic objects, which is one of the most difficult pieces of information for extragalactic objects to measure.

This galaxy also contains a Type Ia supernova, which is the explosion of a white dwarf star that gradually added matter from a companion star.

Like Cepheid variable stars, the brightness of these types of supernovae and how quickly they dim over time allow scientists to calculate their distance. Scientists can use measurements obtained from Cepheid variable stars and Type 1a supernovae to refine our understanding of the expansion rate of the universe, also known as the Hubble Constant.

The Galaxy NGC 6956 lies far away in the constellation Delphinus at a distance of approximately 214 million light-years. It is a barred spiral galaxy. A barred spiral galaxy is a type of spiral galaxy that has a bar-shaped structure of stars in its center. It is a common type of spiral galaxy.

NASA’s Hubble Space Telescope imaged this galaxy. How amazing it is to think that the light (photons) from NGC 6956 that reached Hubble’s lens had been traveling through the vast depths of outer space for 214 million years!

Image Credit: NASA, ESA, and D. Jones (University of California – Santa Cruz); Processing: Gladys Kober (NASA/Catholic University of America)