13.1 billion light years: Galaxy is most distant object in universe
The collection of stars, known as UDFy-38135539, is 13.1 billion light years away – meaning its light has taken almost the whole of the life of the universe to reach the Earth.
When the light photons (units of light) detected by astronomers began their journey, the universe was only 4% of its present age.
The Big Bang which created space, time and the universe occurred only 600 million years earlier.
European scientists reported the discovery in the journal Nature.
They measured the distance to the galaxy by analysing its faint glow of light using the European Southern Observatory (ESO) Very Large Telescope (VLT) in Chile.
Splitting infrared light from the object into its component parts, the astronomers searched for the tell-tale sign of emission from hydrogen gas.
This allowed the team to measure the galaxy’s “redshift” – the amount its light waves shift to the red end of the spectrum. Redshift is similar to the Doppler effect which causes the sound of a police siren to rise and drop in pitch.
As the police car approaches, the sound waves are compressed and shortened relative to a listening observer, causing a higher note to be heard. A lowering of pitch happens when the car recedes and the sound waves are stretched and lengthened.
The same phenomenon occurs on a cosmological scale due to the expansion of the universe. As the distance between an observer on Earth and a far away object lengthens, light from the object is stretched and becomes redder.
In the case of UDFy-38135539, scientists detected a record-breaking redshift of 8.55.
The galaxy is important to astronomers because it dates back to the “epoch of reionisation” – a time in the early universe when radiation from primeval galaxies changed the physical state of surrounding hydrogen gas. Scientists hope galaxies such as UDFy-38135539 will help them better understand the universe’s evolution.
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