In this dramatic picture, spiral galaxy NGC 5091 appears in the foreground. Tilted nearly edge-on , the dust lanes between its spiral arms are clearly visible. The large elliptical galaxy NGC 5090 lies just beyond it - both are about 100 million light years distant in the southern constellation Centaurus . The detailed answer to this question has important implications for determining the nature of dark matter and the measurement of star formation rates. Comparing the overlapping and non-overlapping parts of this and other pairs of galaxies offers a neat way to find the answer.
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