A New 3D Cosmic Map Has Revealed 1 Million Previously Unknown Galaxies.

A view of the Small Magellanic Cloud from the VISTA telescope, with distant galaxies circled in green. (Image courtesy of the ESO/VISTA Magellanic Clouds Survey.)

Astronomers have constructed the greatest 3D depiction of 1 million distant galaxies ever created, which were previously veiled by the Milky Way's dwarf galaxy neighbors, the Magellanic Clouds.

The Magellanic Clouds are a magnificent element of the Southern Hemisphere sky that may be seen with the naked eye. However, the brightness of these dwarf galaxies, combined with their dominance over the night sky, means that the Milky Way's neighbors obscure our view of plenty of more distant galaxies. So, when astronomers see the universe's billions of galaxies, they usually avoid this area of the sky.

"The Magellanic Clouds are magnificent galactic companions, but they frustratingly obstruct some of our view of objects further out," Jessica Craig, a member of the map-building team from the University of Keele, said in a statement (opens in new tab). "Our work is assisting in overcoming this, as well as filling in the gaps in our map of the cosmos."

Craig and her colleagues addressed this issue by shooting the Magellanic Clouds in such high resolution that they can see through the gaps in between stars that comprise these galaxies. The scientists used the Visible and Infrared Survey Telescope for Astronomy (VISTA) at Chile's Paranal Observatory to create these photos.

However, because of dust in the Magellanic Clouds, these progressively faraway "hidden" galaxies are very difficult to spot. To account for this effect, the researchers used the Galactic Australian Square Kilometer Array Pathfinder Survey (GASKAP), a radio telescope capable of peering through the dust between Earth and other galaxies. The GASKAP data enabled the researchers to generate a precise picture of gas and dust in the Magellanic Clouds, accounting for the degree of reddening these factors cause to the galaxies they conceal.

The Small Magellanic Cloud conceals Southern Hemisphere galaxies. (Photos courtesy of ESA/Hubble and Digitized Sky Survey 2)

The human eye cannot distinguish distant galaxies from closer objects due to the large number of light sources in the pictures of the Magellanic Clouds. However, because stars move and distant galaxies stay still, the team was able to properly characterize each light source using data from the star-mapping Gaia telescope.

A second technique was utilized by the researchers to verify the differentiation between distant galaxies and relatively close stars. The wavelength of light from distant galaxies is stretched as the cosmos expands as it moves away from Earth. Longer visible light wavelengths are red, thus astronomers call this lengthening redshift.

The more distant an object, the faster it recedes, and thus the redder its light looks; thus, distant galaxies appear redder than stars. The team might further exclude stars from their data by taking color into account.

Finally, the researchers used machine learning and  AI to organize the galaxies and generate a 3D map of roughly 1 million galaxies.

Craig presented the team's research at the National Astronomy Meeting in mid-July at the University of Warwick in the United Kingdom.