by While the James Webb Space Telescope has been getting a lot of press lately, its predecessor, the Hubble Space Telescope, continues to impress; this time from the galaxy NGC 6956, a near-perfect example of a barred galaxy located about 214 million light-years from Earth.
Barred galaxies, which take their name from the very prominent “bar” of stars that runs through the galactic core, are among the most common types of galaxies in the known universe. constituting about 70% of all galaxies (opens in a new tab). Bar structures are also much more common in galaxies with active galactic nuclei, as gas and other materials are channeled into the galactic core along these bars.
This process helps to destabilize the bar if necessary (opens in a new tab)however, the more mass is channeled to the galactic core, the more unstable the bar becomes, eventually softening the bar into the more traditional spiral formation – like the one in NGC 2985 (opens in a new tab) — which most people think of when they think of a spiral galaxy.
Related: The best Hubble Space Telescope images ever!
According to a image description by NASA (opens in a new tab), this most recent photo of NGC 6956 was aimed at observing Cepheid variable stars, which are stars whose luminosity oscillates between bright and dim at regular intervals. These periods of brightening and dimming are directly related to the actual luminosity of a star, we are able to calculate these variations in apparent luminosity compared to the actual luminosity of the stars, which allows us to determine their distance by relation to us.
It’s a crucial way for astronomers to determine the distance of extragalactic objects like NGC 6956, as there are few other ways to do so that we know of. There are other interesting features of NGC 6956, such as a visible Type Ia supernova, which is the product of a white dwarf star exploding as a result of material accretion from a companion star.
This type of supernova is another key method for determining the distance of distant galaxies, since astronomers are able to measure the rate at which a supernova darkens to help gauge its distance from Earth. And while accurately filling the galactic map is useful in itself, repeated measurements of the distance of these extragalactic objects are an important tool for understanding the current rate of expansion of the universe.
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