TWIN GALAXIES? How ‘dust maps’ are helping astronomers calibrate a multitude of measurements… | Weather Blog

The twin galaxies NGC 4496A and NGC 4496B dominate the frame of this NASA/ESA Hubble Space Telescope image. Both galaxies are in the constellation Virgo, but although they appear side by side in this image, they are at very different distances from Earth and from each other. NGC 4496A is 47 million light years from Earth while NGC 4496B is 212 million light years away. The huge distances between the two galaxies mean that the two do not interact and only appear to overlap due to a fortuitous alignment.

Image credit: ESA/Hubble & NASA, T. Boeker, B. Holwerda, Dark Energy Survey, Department of Energy, Fermilab/Dark Energy Camera (DECam), Cerro Tololo Inter-American Observatory/NOIRLab/National Science Foundation/Association of Universities for astronomy research, Sloan Digital Sky Survey; Acknowledgments: R. Colombari

Random galactic alignments like this offer astronomers the opportunity to delve into the distribution of dust in these galaxies. Galactic dust – the dark tendrils traversing both NGC 4496A and NGC 4496B – adds to the beauty of astronomical images, but also complicates observations for astronomers. Dust in the universe tends to scatter and absorb blue light, making stars darker and redder in a process called “blushing.” Redshift due to dust is different from redshift, which is due to the expansion of space itself. By carefully measuring how the dust in the foreground galaxy affects the starlight of the background galaxy, astronomers can map the dust in the spiral arms of the foreground galaxy. The resulting “dust maps” help astronomers calibrate measurements of everything from cosmological distances to the types of stars populating these galaxies.

Text credit: European Space Agency (ESA)

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