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At the top of this new image, a nearby galaxy reveals its hidden youthful nature. Radiating out of a pink core, the blue spiral arms – which are lit by the fires of hot, young stars – were discovered in ultraviolet light by NASA’s Galaxy Evolution Explorer.
The galaxy NGC 4625, which lies 31 million light-years away in the constellation Canes Venatici, always seemed like just a plain old galaxy made up of 10 billion-year-old stars. The unexpected spiral arms, which extend four times further than the core, are inhabited primarily by one billion-year-old stars.
This remarkable mix of young and old may be a picture of what our Milky Way looked like in its past.
“We do not fully understand how stars were created in our galaxy,” said Barry Madore of the Carnegie Observatories, co-author of a paper in the July issue of Astrophysical Journal Letters. “This nearby galaxy represents one of our possible histories, in which stars developed first in the galaxy core and then later in the arms.”
The neighboring galaxy in this image is NGC 4618. Why this companion does not have arms is a mystery, but astronomers suspect that the arms in NGC 4625 may have been triggered by interactions with NGC 4618.
Credit: NASA/JPL-Caltech/Carnegie Observatories/DSS |
