Beyond the Clouds: Discovering the Galaxy Behind the Galaxy

There are hundreds of billions of galaxies in the universe, each containing billions of stars, and they are found in every part of the sky. But in some directions, nearby galaxies block the view of the more distant cosmos.

Now a team from Keele University has created the largest map of a previously hidden galaxy. Jessica Craig presented their work this week at the National Astronomy Meeting at the University of Warwick.

Astronomers saw the Magellanic Clouds, a pair of galaxies visible from the southern hemisphere that are so close to us that they can be seen with the naked eye. The two galaxies occupy large areas of the sky, blocking the view of more distant galaxies. Because of this, astronomers looking for distant galaxies usually avoid this part of the sky.

Using the VISTA Survey Telescope in Chile, the team photographed two nearby galaxies in high enough definition to be able to see through the gaps between the stars in each. That way they can see galaxies that are farther away, which appear dimmer and redder than they really are because of the dust that is still in front of them.

The solution is to use radio telescopes, and in this case the Galactic Australian Square Kilometer Array Pathfinder Survey (GASKAP) provides a detailed map of the gas in the Magellanic Cloud, allowing dust levels to be measured, and therefore how much the star is blushing.

A further concern is to distinguish stars from galaxies, and there are so many that this is impossible to do by hand. So Keele’s team used data from the Gaia observatory to measure small shifts in the positions of stars over time, while galaxies that were much more distant remained in the same place.

Galaxies are also redder than brighter stars, so color helps remove more stars from the data set. Color also shows how far away the galaxy is (via the redshift that results from the expansion of the Universe).

Machine learning, where software uses artificial intelligence tools, does the last kind of data residue. All this work led to the largest ever 3D galaxy map previously hidden behind the Magellanic Cloud, which includes about 1 million galaxies.

Jessica Craig commented: “The Magellanic clouds are wonderful companions of the galaxy, but unfortunately they block some of our view of objects farther away. Our work is helping to address them, and in the process helping to fill gaps in our universe map.”

related links

Royal Astronomical Society

Chemistry of the Stars, the Universe and Everything In It

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NASA releases first full set of images from the $10 billion James Webb Space Telescope

Washington DC (UPI) July 12, 2021

NASA on Tuesday unveiled the first full collection of images taken by the James Webb Space Telescope – featuring the kind of photos engineers had in mind when they first assembled the telescope in the 1990s. The space agency unveiled a collection of five images from the $10 billion telescope during a Tuesday night event at the Goddard Space Flight Center in Greenbelt, Md. The images were released simultaneously on social media and NASA’s website. “This first image of … read more

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