Post #419

These twin galaxies, NGC 4496A & B are in the center of the frame of this image from NASA Hubble. Even though these galaxies look like they are close together, they are at vastly different distances from both Earth and one another. NGC 4496A is 47 million light-years from Earth while NGC 4496B is 212 million light-years away. These galaxies aren’t interacting due to the distance between them, but appear to overlap in this image due to a chance alignment. This gives astronomers an opportunity to observe the distribution of dust in these galaxies. Dust absorbs starlight, making stars seem dimmer and shifting their light towards longer wavelengths. By measuring how starlight from background galaxies is affected by dust in intervening galaxies, astronomers can map out where the dust is in the foreground galaxy’s spiral arms. The resulting “dust maps” help astronomers calibrate measurements of everything from cosmological distances to the types of stars populating galaxies.