Growth by Interaction
This ultraviolet/visible-light composite image shows one-way galaxies may grow from interaction. The composite was created with ultraviolet imagery taken by NASA's Galaxy Evolution Explorer (GALEX), and visible-light pictures from the Digital Sky Survey (DSS).
The galaxy covered by a red haze is NGC 1512. The red coloration depicts the visible-light appearance of this galaxy - this glow comes from the galaxy's older, more evolved stars. Meanwhile, the bluish-white ring shows what NGC 1512 looks like in ultraviolet light, a wavelength regime principally tracing young massive stars. This inner ring connects to tightly wound spiral arm segments. The dark blue arms coming off of the inner ring are formed due to the strong gravitational perturbation associated with galactic companion NGC 1510 - which is shown as the glowing yellow spot located southeast (down and right) of NGC1512. The two galaxies are separated by a mere 49,300 light-years, leading astronomers to suspect that a close encounter is currently in progress.
The wisps of blue extending far beyond the main disks of these galaxies (especially NGC1512) are groupings of young stars that probably formed within the last few hundred million years. Astronomers suspect that these stellar births were most likely triggered by the gravitational interaction between NGC 1512 and NGC 1510. The lack of red haze overlapping the outer wisps of blue means that this extended star formation is seen preferentially in the ultraviolet. Astronomers refer to this as an "extended ultraviolet disk." Astronomers suspect the extended disk is an indication that the galaxy is growing. They think this unexpected star formation will augment NGC 1512's evolved disk to a varied degree depending on how long interaction-induced stellar births continue to consume the outer disk gas.
This image is a false color composite where, near-ultraviolet light is green, far-ultraviolet light is blue, and visible-light is red.
April 11, 2007
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