irregular galaxy
Quick Summary
Irregular galaxies are a class of galaxies that lack a distinct, symmetrical shape and a central nucleus, unlike spiral or elliptical galaxies. They often appear as chaotic, grainy assemblages of luminous areas and are typically bluer than spiral galaxies due to a higher concentration of young, hot stars.1
Historically, irregular galaxies were categorized into Irr I and Irr II types. Irr I galaxies are more common and seem to be a continuation of spiral galaxy classes, while Irr II systems are rarer, redder, and often chaotic, frequently resulting from galaxy interactions like tidal distortions or mergers. Modern classification systems, such as de Vaucouleurs', offer more detailed descriptions but are less commonly used than Hubble's basic framework.12
Evidence suggests that many galaxies, including our own Milky Way, grow through collisions and mergers with smaller galaxies. These interactions can significantly alter a galaxy's structure and appearance over time.3
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