The blue swirls of spiral galaxy NGC 6956 shine brightly against an inky black background. NGC 6956 is a barred spiral galaxy. It is a type of spiral galaxy that has a star-shaped structure in its centre. This galaxy can be found in the constellation Delphinus. Delphinus is 214 million light-years away from Earth.
Scientists imaged NGC 6956 with NASA’s Hubble Space Telescope to study its Cepheid variable stars. These stars brighten and dim at regular intervals. The period of Cepheid variable stars is a function of their brightness. Scientists can calculate their distance by measuring how bright these stars appear from Earth and comparing it to their actual brightness. So, these stars are extremely useful in determining cosmic object distance. This is one of the most difficult pieces of information to measure for extragalactic objects.
This galaxy also has a Type Ia supernova. It was caused by the explosion of a white dwarf star that was gradually accreting matter from a companion star. The brightness of these types of supernovae and how quickly they dim over time allow scientists to calculate their distance. Scientists can use data from Cepheid variable stars and Type Ia supernovae to improve their understanding of the Hubble Constant or the rate of expansion of the universe.
