From time immemorial, philosophers and scholars have contemplated the beginning of time and have even tried to determine when all things began. Only in the age of modern astronomy have we come close to answering this question with a certain degree of certainty.
According to the most accepted cosmological models, the Universe began with the Bang Bang about 13.8 billion years ago.
However, astronomers are still unsure of what the primitive universe was like, as this period coincided with the cosmic “dark ages.” Therefore, astronomers continue to push the boundaries of their instruments to see when the first galaxies formed.
Thanks to new research by an international team of astronomers, the oldest and most distant galaxy ever observed in our universe has been identified (GN-z11).
The team, whose research has recently been published in the journal Nature Astronomy, was directed by Linhua Jiang of the Kavli Institute of Astronomy and Astrophysics and Professor Nobunari Kashikawa of the University of Tokyo.
They were accompanied by researchers from the observatories of the Carnegie Institution for Science, the Steward Observatory, the Geneva Observatory, Peking University and the University of Tokyo.
Simply put, the Cosmic Dark Ages began about 370,000 years after the Big Bang and continued for another 1 billion years.
At that time, the only light sources were photons released earlier, which can still be detected today as cosmic microwave backgrounds (CMBs), and those released by neutral hydrogen atoms. The light from these photons is so displaced due to the expansion of the Universe that they are invisible to us today.
This effect is known as “redshift,” where the wavelength of light lengthens (or “shifts” toward the red end of the spectrum) as it passes through the expanding cosmos. on the way to reach us.
For objects approaching our galaxy, the effect is reversed, with the wavelength shortened and shifted to the blue end of the spectrum (also known as “blueshift”). .
For nearly a century, astronomers have used these effects to determine the distance of galaxies and the speed at which the universe is expanding. In this case, the research team used the Keck I telescope in Maunakea, Hawaii, to measure the redshift of GN-z11 to determine its distance.
The results they obtained indicated that it is the most distant (and oldest) galaxy ever observed. As Kashikawa explained in a press release from the University of Tokyo:
“According to previous studies, the GN-z11 galaxy appears to be the farthest detectable galaxy from us, 13.4 billion light-years, or 134 million kilometers (that is, 134 followed by 30 zeros). But measure and verify this distance is not an easy task “.
Specifically, the team examined the carbon emission lines from GN-z11, which were in the ultraviolet range when they left the galaxy and moved by a factor of 10, to the infrared (0 , 2 micrometers), on reaching Earth.
This level of redshift indicates that this galaxy existed as observed approximately 13.4 billion years ago, that is, only 400 million years after the Big Bang.
At this distance, GN-z11 is so far away that it defines the very limit of the observable Universe itself. Although this galaxy had been observed in the past (by Hubble), it needed the resolution power and spectroscopic capabilities of the Keck Observatory to make accurate measurements.
This was done as part of the survey of the multi-object spectrograph for infrared scanning (MOSFIRE), which captured in detail the emission lines of GN-z11.
This allowed the team to produce distance estimates for this galaxy that were improved by a factor of 100 over the measurements that had been made previously. Kashikawa said:
“The Hubble Space Telescope detected the signature several times in the GN-z11 spectrum. However, even Hubble can’t solve the ultraviolet emission lines to the degree we needed. So we turned to a terrestrial spectrograph. more up-to-date, an instrument for measuring emission lines, called MOSFIRE, which is mounted on the Keck I telescope in Hawaii. “
If later observations can confirm the results of this latest study, astronomers can say with certainty that GN-z11 is the most distant galaxy ever observed. By studying objects like this, astronomers hope to be able to illuminate a period in cosmic history when the Universe was only a few hundred million years old.
This period coincides with the fact that the Universe began to emerge from the “Dark Age”, when the first stars and galaxies formed and filled the primitive universe with visible light.
By studying them, astronomers hope to learn more about how the large-scale structures of the Universe later evolved. This will have the help of next-generation telescopes, such as the James Webb Space Telescope (JWST), launched on October 31, 2021.
These instruments will even allow astronomers to study the same “dark ages”, a time when the only light that is not CMB was the line of rotation of neutral hydrogen, at the wavelength of the microwave (21 cm).
To be able to explore the beginnings of the Universe itself and see how the first stars and galaxies form. What an exciting time it will be!
The observations that made this research possible were conducted as part of the time-exchange program between the Keck Observatory and the Subaru Telescope in Maunakea, Hawaii.
This article was originally published by Universe Today. Read the original article.