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Around the Schools: Faculty of Arts and Sciences

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As the old saying goes, records are meant to be broken. In April, the record for farthest-known object in the universe fell — busted by a gigantic explosion brighter than an entire galaxy of stars.

Astronomers at the Harvard-Smithsonian Center for Astrophysics, along with colleagues elsewhere in the United States and the United Kingdom, discovered the record breaker — a spectacular stellar blast known as a gamma-ray burst. The star that exploded so dramatically was located about 13 billion light-years from Earth, making it the most distant known object. (One light-year is 6 trillion miles, the distance a photon of light travels in a year’s time.)

The entire visible universe extends 13.7 billion light-years from Earth.

Therefore, the burst, known as GRB 090423 for the date it was detected, is located almost as far from Earth as we could possibly see.

Since it takes light time to cover any distance, a telescope has been compared to a time machine. When we study a galaxy a million light-years away, we see it as it was a million years ago (because that’s how long it took for the galaxy’s light to reach Earth). As a result, you also could say that GRB 090423 was the youngest object ever seen. The burst exploded onto the scene when the universe was a mere 630 million years old (only one-twentieth its current age).