Jul 19. () –
The space telescope NASA/ESA Hubble has captured an image that shows the irregular dwarf galaxy NGC 5238, located 14.5 million light years from Earth in the constellation Canes Venatici.
NASA has noted that its blob-like appearance looks more like a large star cluster than a classic image of a galaxy, and that its lackluster appearance belies its complicated structure, which is the subject of a great deal of research.
As the image reveals, Hubble can make out the galaxy’s countless stars, as well as their associated globular clusters: bright points both within and around the galaxy, surrounded by even more stars.
Astronomers theorize that NGC 5238 may have had a close encounter with another galaxy as recently as 1 billion years ago. NGC 5238’s distorted shape provides evidence of this interaction.
As the two galaxies interacted, their gravity caused distortions in the distribution of stars in each galaxy. There is no nearby galaxy that could have caused this disturbance, so astronomers believe that NGC 5238 swallowed a smaller satellite galaxy.
Astronomers are searching for traces of the consumed galaxy by closely examining the star population in NGC 5238, thanks to Hubble’s excellent resolution.
A telltale sign of the smaller galaxy would be star clusters with different properties than most of the other stars in NGC 5238, indicating that they originally formed in a separate galaxy. Another sign would be a burst of star formation that occurred abruptly around the same time the two galaxies merged.
The Hubble data used to create this image will help astronomers determine the history of NGC 5238.
Despite their small size and unremarkable appearance, it is not unusual for dwarf galaxies like NGC 5238 to advance our understanding of galaxy formation and evolution.
One of the main theories of galaxy evolution is that galaxies formed “bottom up” in a hierarchical manner: Star clusters and small galaxies were the first to form from gas and dark matter..
Over time, gravity gradually assembled these smaller objects into galaxy clusters and superclusters, explaining the shape of the larger structures we see in the universe today.
An irregular dwarf galaxy like NGC 5238 merging with a smaller companion is just the kind of event that could have initiated the process of galaxy assembly in the early universe. Hubble observations of the tiny NGC 5238 may help test some of the most fundamental ideas about how the universe evolves.
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