New 3D space map reveals 1 million previously hidden galaxies

Astronomers have created the largest ever 3D map of 1 million distant galaxies that would otherwise be obscured by the Milky Way’s neighboring dwarf galaxies, the Magellanic Clouds.

Magellanic Clouds are irregularly shaped galaxies that are a stunning feature of the sky in the Southern Hemisphere and are visible to the naked eye. But the brightness of these dwarf galaxies, coupled with the fact that they occupy a large area of ​​the night sky, means that the Milky Way’s neighbors block our view of many much more distant galaxies. Therefore, when astronomers observe the billions of galaxies in the universe, they try to avoid this part of the sky.

“Magellan clouds are great galactic companions, but they unfortunately partially block our view of objects farther away,” said Keele University astronomer and member of the mapping team Jessica Craig. (will open in a new tab). “Our work helps overcome this and in the process helps fill in the gaps in our map of the universe.”

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Craig and her colleagues solved this problem by photographing the Magellanic Clouds at such high resolution that they could see the gaps between the stars that make up these galaxies. To take these images, the team turned to the Visible and Infrared Telescope for Astronomy (VISTA), based at the Paranal Observatory in Chile.

But these increasingly distant “hidden” galaxies are particularly difficult to see because they appear dimmer and redder than the dust in the Magellanic Clouds. To explain this effect, the team turned to a radio telescope, the Australian Galactic Survey Square Kilometer Array (GASKAP), which can look through the dust between Earth and distant galaxies. The GASKAP data allowed scientists to create a detailed map of the gas and dust in the Magellanic Clouds and thus take into account the amount of “reddening” of these factors in the galaxies they obscure.

The Small Magellanic Cloud hides galaxies in the Southern Hemisphere. (Image credit: ESA/Hubble and Digitized Sky Survey 2)

Due to the sheer number of light sources in Magellanic Cloud images, the human eye alone cannot distinguish distant galaxies from closer objects. But stars change their positions while distant galaxies stay in one place, so the team was able to use data from the Gaia observatory to compile star maps to correctly classify each light source.

Astronomers used the second method to confirm the difference between distant galaxies and relatively nearby stars. Because the universe is expanding as distant galaxies move away from Earth, the wavelength of light from these galaxies is stretched. Longer wavelengths of visible light are red, which is why astronomers refer to this as a lengthening redshift.

The further away an object is, the faster it moves away, and the redder its light appears, which is why distant galaxies are redder than stars. By taking color into account, the team could further exclude stars from their data.

Finally, the astronomers used machine learning and artificial intelligence to organize the galaxies and create a three-dimensional map of approximately 1 million galaxies.

Craig presented the group’s findings in mid-July at the National Astronomical Meeting held at the University of Warwick in the UK.

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