Hubble Space Telescope Spots Cepheid Variables in NGC 6956

by johnsmith

Astronomers using the NASA/ESA Hubble Space Telescope have imaged the barred spiral galaxy NGC 6956, which is found in the constellation of Delphinus.

This Hubble image shows NGC 6956, a barred spiral galaxy some 215 million light-years away in the constellation of Delphinus. Image credit: NASA / ESA / D. Jones, University of California, Santa Cruz / Gladys Kober, NASA & Catholic University of America.

NGC 6956 is a barred spiral galaxy, a common type of spiral galaxy with a bar-shaped structure of stars in its center.

Otherwise known as LEDA 65269, IRAS 20415+1219 and UGC 11619, it lies approximately 215 million light-years away in the constellation of Delphinus.

The Hubble astronomers observed NGC 6956 to study its Cepheid variables, which are stars that brighten and dim at regular periods.

“Since the period of Cepheid variable stars is a function of their brightness, we can measure how bright these stars appear from Earth and compare it to their actual brightness to calculate their distance,” the astronomers explained.

“As a result, these stars are extremely useful in determining the distance of cosmic objects, which is one of the hardest pieces of information to measure for extragalactic objects.”

NGC 6956 also contains a Type Ia supernova, which is the explosion of a white dwarf star that was gradually accreting matter from a companion star.

“Like Cepheid variable stars, the brightness of these types of supernovae and how fast they dim over time enables scientists to calculate their distance,” the researchers said.

“We can use the measurements gleaned from Cepheid variable stars and Type Ia supernovae to refine our understanding of the rate of expansion of the Universe, also known as the Hubble constant.”

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