Astronomers have created the largest 3D map yet of 1 million distant galaxies that would otherwise be obscured by the Milky Way’s dwarf galaxy neighbors, the Magellanic Clouds.
The Magellanic Clouds are irregularly shaped galaxies which are a stunning feature of the southern hemisphere sky 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 WayThe neighbors of block our view of many more distant galaxies. So when astronomers study the billions of galaxies in the universethey tend to avoid this part of heaven.
“The Magellanic Clouds are beautiful galactic companions, but unfortunately they block part of our view of more distant objects,” said Jessica Craig, an astronomer from the University of Keele and a member of the mapping team a statement (opens in new tab). “Our work is helping to overcome that and helping to fill in the gaps in our map of the universe.”
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Craig and her colleagues addressed this problem by photographing the Magellanic Clouds at high enough resolution that they could see through the gaps between the clouds Stars that make up these galaxies. To take these images, the team turned to the Visible and Infrared Survey Telescope for Astronomy (VISTA) at the Paranal Observatory in Chile.
But these increasingly distant “hidden” galaxies are particularly difficult to see because they appear fainter and redder than they are due to dust in the Magellanic Clouds. To explain this effect, the team turned to a radio telescope, the Galactic Australian Square Kilometer Array Pathfinder Survey (GASKAP), which can see through the dust between Earth and distant galaxies. The GASKAP data allowed scientists to create a detailed map of gas and dust in the Magellanic Clouds, explaining the extent of the “redness” these factors cause in the galaxies they occlude.
Because of the sheer number of light sources in the images of the Magellanic Clouds, the human eye alone cannot distinguish distant galaxies from closer objects. But stars shift position while distant galaxies remain in the same place, allowing the team to use data from stellar mapping Gaia Observatory to properly categorize each light source.
The astronomers used a second technique to confirm the distinction between distant galaxies and relatively nearby stars. As the universe expands 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 call this lengthening redshift.
The further away an object is, the faster it is moving away and the redder its light appears, so distant galaxies are redder than stars. By considering color, the team was able to further eliminate stars from their data.
Finally, the astronomers applied machine learning and artificial intelligence to order the galaxies and create a 3D map of an estimated 1 million galaxies.
craig presented the team’s results In mid-July at the National Astronomy Meeting at the University of Warwick in the UK
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