(ORDO NEWS) — Since time immemorial, philosophers and scientists have speculated about the beginning of time and even tried to determine when it all began. Only in the era of modern astronomy have we approached the answer to this question with a sufficient degree of certainty.
According to the most widespread cosmological models, the universe began with the Big Bang about 13.8 billion years ago.
Despite this, astronomers are still not sure what the early universe looked like, as this period coincided with the cosmic “Dark Ages.” Therefore, they continue to expand the capabilities of their instruments to see when the earliest galaxies formed.
Thanks to a new study by an international team of astronomers, the oldest and most distant galaxy observed in our universe to date (GN-z11) has been identified.
The group, whose research was recently published in the journal Nature Astronomy, was led by Linghua Jiang of the Kavli Institute of Astronomy and Astrophysics and Professor Nobunari Kashikawa of the University of Tokyo.
They were joined by researchers from the observatories of the Carnegie Institute of 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 either photons released earlier – which can still be detected today as the cosmic microwave background (CMB) – or those released by neutral hydrogen atoms. The light of these photons is so displaced by the expansion of the universe that they are invisible to us today.
This effect is known as “redshift”, when the wavelength of light lengthens (or “shifts” towards the red end of the spectrum) as it travels through the ever-expanding space on its way to us.
For objects approaching our galaxy, the effect is reversed: the wavelength shrinks and shifts towards the blue end of the spectrum (also known as “blue shift”).
For nearly a century, astronomers have used these effects to determine the distance to galaxies and the rate at which the universe is expanding. In this case, the research team used the Keck I telescope in Maunakey, Hawaii to measure the redshift of GN-z11 and determine the distance to it.
Their results showed that it is the farthest (and oldest) galaxy ever observed. As Kasikawa explained in a press release from the University of Tokyo:
“According to previous research, the galaxy GN-z11 appears to be the farthest detectable galaxy from us, at 13.4 billion light years, or 134 nonillion kilometers (that’s 134 followed by 30 zeros). But measuring and checking such a distance is not easy. ”
Specifically, the team examined the carbon emission lines emanating from GN-z11, which were in the ultraviolet range when they left the galaxy and were shifted 10 times – in the infrared range (0.2 micrometers) – by the time they reached Earth.
This redshift level indicates that this galaxy existed about 13.4 billion years ago, that is, just 400 million years after the Big Bang.
GN-z11 is so far away that it defines the very border of the observable universe! Although this galaxy was observed in the past (by Hubble), accurate measurements required the resolution and spectroscopic capabilities of the Keck Observatory.
This was done as part of the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) survey, during which GN-z11 emission lines were captured in detail.
This allowed the team to produce distance estimates for this galaxy that were 100 times better than any previous measurements.
“The Hubble Space Telescope has detected a signature in the GN-z11 spectrum several times. However, even Hubble cannot resolve ultraviolet radiation lines to the extent that we needed. Therefore, we turned to a more modern ground-based spectrograph, an instrument for measuring emission lines, called MOSFIRE, which is installed on the Keck I telescope in Hawaii. ”
If subsequent observations can confirm the results of this study, then astronomers can confidently say that GN-z11 is the farthest galaxy ever observed. By studying such objects, astronomers hope to shed light on a period of cosmic history when the universe was only a few hundred million years old.
This period coincides with the time when the Universe began to emerge from the “Dark Ages”, the first stars and galaxies formed and filled the early Universe with visible light.
By studying them, astronomers hope to learn more about how the large-scale structures of the universe subsequently evolved. Next-generation telescopes such as the James Webb Space Telescope (JWST), which is scheduled to launch on October 31, 2021, will help.
The observations that made the study possible were made as part of a time exchange program between the Keck Observatory and the Subaru Telescope in Maunakey, Hawaii.
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