Scientists have discovered the most faraway galaxy to date, all thanks to another galaxy so huge it acts as a magnifying glass.

Astronomers using NASA's Hubble Space Telescope were examining the star formation patterns in two distant galaxy clusters, including one called IRC 0218, when they chanced upon a galaxy so large that it distorts the light coming from other objects situated behind it. The magnifying galaxy, which is found 9.6 billion light years away, has paved the way for the discovery of another, more distant galaxy 10.7 billion light years from Earth.

Compared to newer galaxies, the magnifying galaxy is not as massive as it sounds, weighing only 180 billion times more than our sun. It is, however, one of the largest discovered galaxies that formed more than 9 billion years ago. The research team believes that the galaxy has continued to grow by accumulating stars and dark matter from nearby galaxies over the past 9 billion years. Over time, this galaxy will become more massive than Milky Way and will have more dark matter too.

Although cosmic magnifiers are not rare, lead researcher Kim-Vy Tran of Texas A&M University says the chances of finding one that was neatly aligned with another galaxy in the background is a special treat. Tran uses the analogy of an actual magnifying lens to explain.

"Imagine holding a magnifying glass close to you and then moving it much farther away," Tran says. "When you look through a magnifying glass held at arm's length, the chances that you will see an enlarged object are high. But if you move the magnifying glass across the room, your chances of seeing the magnifying glass nearly perfectly aligned with another object beyond it diminishes."

Tran was analyzing spectrographic data about the IRC 0218 galaxy cluster in Hawaii's W.M. Keck Observatory when she detected hot hydrogen gas, a telltale sign of star formation, coming up from the giant galaxy. At first, the scientist thought she had made a mistake because previous observations show the galaxy has long stopped forming stars.

However, after analyzing images taken by Hubble's Advanced Camera for Surveys, Tran discovered that the spot of hot hydrogen came from another, more distant galaxy, which appeared as a small, bluish smear that indicated the formation of new stars. Analyzing the faraway galaxy's distribution of light, which revealed a bright compact nucleus, Tran and her team inferred that the newly discovered galaxy takes the shape of a spiral.

The team's findings were published in the July 10 issue of The Astrophysical Journal Letters. 

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