Big Bang theory: Astronomers discover oldest galaxy in universe’s ‘Dark Age’

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The dawn of existence and time itself has long fascinated philosophers and scientists. But it is only since the advent of modern technology in recent decades that the world’s greatest minds have even begun to properly comprehend the concept of the Big Bang.

Current cosmological models commonly accept the cosmos kicked-off with the Big Bang approximately 13.8 billion years ago.

From previous studies, the galaxy GN-z11 seems to be the farthest detectable galaxy from us, at 13.4 billion light years, or 134 nonillion km

Professor Nobunari Kashikawa

However, astronomers are still uncertain about what the nascent Universe looked like during this early period dubbed the cosmic ‘Dark Age’.

But after pushing cutting-edge instruments to their very limits, astronomers have now been rewarded with the discovery of the oldest and most distant galaxy ever observed.

The cosmic Dark Ages are recognised as starting 370 thousand years after the Big Bang and lasted for another one billion years.

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The only light sources during this period were either the photons, still detectable today as the cosmic microwave background, and emissions made by neutral hydrogen atoms.

The Universe’s expansion means these photons’ light is so shifted they are largely invisible to astronomers.

This effect is known as “redshift,” is a phenomenon not dissimilar to the Doppler effect, where the wavelength of light is elongated – or ‘shifted’ – towards the red end of the spectrum as it passes through the acceleratingly-expanding cosmos on route to Earth-bound observers.

Objects moving closer to our galaxy engineer a reverse effect.

This sees the wavelength shortening, shifting towards the blue end of the spectrum, in a phenomenon known as ‘blueshift’.

Astronomers have long used these effects to accurately calculate galaxies’ distance and the rate of the Universe’s expansion.

The new results obtained with the help of Hawaii’s Keck I telescope confirms GN-z11 is the farthest – and therefore oldest – galaxy ever observed.

Professor Nobunari Kashikawa of the University of Tokyo, one of the study’s lead authors, said in a statement: “From previous studies, the galaxy GN-z11 seems to be the farthest detectable galaxy from us, at 13.4 billion light-years, or 134 nonillion km.

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“But measuring and verifying such a distance is not an easy task.”

A ‘nonillion’ is a such an excessively-large number it involves 30 zeros.

The researchers examined the carbon emissions lines emanating from GN-z11, lying in the ultraviolet range when they departed the galaxy, before significantly shift the infrared end of the scale by the time they arrive at Earth.

Such significant redshift indicates this galaxy existed approximately 13.4 billion years ago – a mere 400 million years following the Big Bang.

GN-z11 is consequently so distant it actually defines the very boundary of the observable Universe.

Although this galaxy had been already been observed by NASA’s Hubble Space Telescope, the Keck Observatory has only now been able to make accurate measurements.

Specifically, it was the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) survey that allowed the researchers to produce distance estimates improved by a factor of 100 over previous measurements.

Professor Kashikawa added: ”The Hubble Space Telescope detected the signature multiple times in the spectrum of GN-z11. However, even the Hubble cannot resolve ultraviolet emission lines to the degree we needed.

“So we turned to a more up-to-date ground-based spectrograph, an instrument to measure emission lines, called MOSFIRE, which is mounted to the Keck I telescope in Hawaii.”

However, astronomers will have to wait a while longer before more observations can confirm with certainty GN-z11 really is the most distant galaxy ever observed.

The mysterious ‘Dark Age’ occurred when the first stars and galaxies formed and illuminate the early Universe.

Studies such as this should shed light of their own about how the large-scale structures of the Universe evolved.

Astronomers expect such research will rapidly-accelerate when next-gen telescopes like James Webb begin operating.

These instruments will eventually allow astronomers to study the poorly-understood ‘Dark Age’ period with unparalleled precision.

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