While the James Webb Space Telescope has been receiving a lot of press lately, its predecessor, the Hubble Space Telescope, has continued to impress; This timeline of the galaxy NGC 6956, a near-perfect example of a barred galaxy located approximately 214 million light-years from Earth.
Barred galaxies, which get their name from the very prominent “bar” of stars that intersects the galaxy’s nucleus, are the most common type of galaxy in the known universe. make up an estimated 70% of all galaxies (opens in new tab), Bar structures are far more common in galaxies with active galactic nuclei, because along these bars gas and other material is fed towards the galactic core.
this process eventually helps destabilize the bar (opens in new tab)However, the more mass funneled to the galactic core, the more unstable the bar becomes, eventually softening the bar into a more traditional spiral formation – Like NGC 2985 (opens in new tab) – This is what most people think of when they think of a spiral galaxy.
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according to a Image description by NASA (opens in new tab)This most recent photo of NGC 6956 was for viewing Cepheid variable stars, which are stars whose brightness oscillates between bright and dim at regular intervals. This period of brightening and dimming is directly related to a star’s true brightness, we are able to calculate these variations in apparent brightness for the stars’ true brightness, which allows us to determine their distance from us.
It is an important way for astronomers to determine the distance to extragalactic objects like NGC 6956, as there are few other ways to do so that we currently know of. NGC 6956 has other interesting features, such as a visible Type Ia supernova, which is the product of the explosion of a white dwarf star as a result of accretion of material from a companion star.
This type of supernova is another important way to determine the distance to distant galaxies, as astronomers are able to measure how quickly a supernova dims to help measure its distance from Earth. And while accurately filling out the galactic map is useful in its own right, repeated measurements of the distances to these extragalactic objects are an important tool for understanding the current rate of expansion in the universe.
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