File Photo: Xinhua

An international team from the Institute of Astronomy and Astrophysics at Peking University confirmed the existence of a galaxy 13.4 billion lightyears away, which is the most distant astronomical object ever discovered.
 
The astronomers deduce that the galaxy, GN-z11, was formed about 400 million years after the Big Bang, and its light traveled 13.4 billion years to reach earth’s telescopes.

The team, led by Jiang Linhua, published two papers on the findings in the journal Nature Astronomy on Monday. The discovery is of great significance in understanding the formation of galaxies and stars in the early universe and opens a window for studying the very early celestial bodies in the universe.

By measuring the redshift of light, usually denoted as Z, scientists can determine the age of a galaxy. The larger the redshift number is, the older and more distant the galaxy is. The galaxy found by Jiang’s team is called GN-z11 because 400 million years after the Big Bang corresponds to a redshift of about 11 years.

In April 2017, Jiang's team made a deep spectral observation of GN-z11 using one of the world's most advanced ground-based infrared telescopes, the Keck Observatory telescopes on Maunakea in Hawaii. Based on the spectral analysis, the accurate redshift of the galaxy was 10.957, confirming it to be a galaxy 13.4 billion light years away.

The work suggests that existing large astronomical instruments are capable of detecting some of the spectra of early galaxies like GN-z11.

Not only did the team read the exact redshift number in the spectrum, it also found that the galaxy is  rich in non-hydrogen and non-helium elements. The message is GN-z11 was not the first galaxy in the universe.

In addition, the team detected a burst from the direction of the galaxy, which appears in a bright near infrared spectrum. In less than three minutes, the galaxy appears to have increased its brightness hundreds of times. Theoretical calculations suggest that the spectrum may have come from a gamma-ray burst from GN-z11 (a very short, high-energy wave of light). 

The earliest known gamma-ray burst occurred about 500 million years after the Big Bang. If the "surprise" of the GN-z11 spectrum can be confirmed, Jiang and his team will have also discovered the oldest and most distant gamma-ray burst.

Global Times