James Webb discovers two distant galaxies and pushes the boundaries of the universe

The Magnificent Discoveries of James Webb! Since the beginning of its observations, NASA’s space telescope has never ceased to amaze us. He just dazzled us once again with images from two galaxies, one of which is the most distant ever observed. This discovery published in The Astrophysical Journal Letters speeding up the onset of the “cosmic dawn” by several hundred million years.

James Webb discovers the most distant starlight known to date

The James Webb Space Telescope discovered these galaxies, named GLASS-z12 and GLASS-z10, in the Pandora cluster. It is a supercluster of more or less 500 galaxies. It is about 4 billion light years from Earth.

Of these two galaxies, GLASS-z12 is now the most distant galaxy we know of. It’s on the edge of the universe! It would have formed just under 350 million years (redshift of 12.5) after the big bang, which occurred 13.8 billion years ago. This galaxy beats the “previous record” held by the galaxy GN-z11b, which existed 400 million years after the birth of the universe. The Hubble Space Telescope and the Keck Observatory discovered it in 2016. This observatory culminates at 4100 meters above sea level on the island of Hawaii. GLASS-z10, the second galaxy discovered by James Webb, would have formed 450 million years after the big bang at a redshift of 10.5. Future spectroscopic measurements still need to confirm the distances between these early sources that emit extreme luminosity.

Also called redshift, the redshift of a galaxy is an increase in the wavelength of light emitted by the galaxy. This increase in wavelength is due to the distance of the galaxy from the observer due to the expansion of the universe. Galaxies with a high redshift are further away than those with a lower redshift.

Also read: A galaxy cluster that deflects light helps solve some of the mysteries of the universe

This distant galaxy challenges our knowledge of the universe

The galaxies in the Pandora cluster represent only 5% of its mass!
Credits: NASA, ESA, J. Merten (Institute for Theoretical Astrophysics, Heidelberg/Bologna Astronomical Observatory) and D. Coe (STScI)

Until today, astronomers estimated that the first stars in the universe appeared between 250 and 350 million years after the beginning of the universe. The first primitive galaxies would have formed more or less 550 million years after the big bang.

The Dark Age of the Universe is the period immediately after the Big Bang, which occurred nearly 14 billion years ago. At that time, the universe consisted only of a vast dark “gaseous nebula”. It consisted of a mixture of neutral hydrogen atoms in which stars and galaxies do not yet exist. In the dark period of the universe, no electromagnetic radiation occurs.

The end of this dark age in the universe is called the Cosmic Dawn. This period is characterized by the formation of the first stars in the universe and because astronomers call the reionization of the universe. During this period, radiation from population III stars ionizes the atoms of the universe. These stars are the very first to illuminate the universe.

The discovery of these two galaxies GLASS-z12 and GLASS-z10 by James Webb challenges our knowledge of the universe. In fact, they were formed much earlier. It seems that the end of the dark ages of the universe also marks the beginning of the cosmic dawn. This is accompanied by the formation of galaxies. This period finally passed faster than expected after the big bang.

Also read: James Webb discovers a knot of galaxies forming around a quasar!

very bright galaxies

Thanks to the James Webb Space Telescope, astronomers have seen that the galaxies GLASS-z12 and GLASS-z10 are very bright. They are very different from the galaxies closer to us.

The researchers explain this strong brightness with two hypotheses. In the first, they emphasize that these are extremely massive galaxies that contain many low-mass stars, as is rather the case in recent galaxies.

In the second hypothesis, astronomers believe that these galaxies would be composed of stars from populations III. These primitive stars are currently only hypothetical. They would be very massive stars of 100 to 300 solar masses and extraordinarily brilliant. Their lifespans were short on an astronomical scale, as they would have consumed their thermonuclear fuel within an estimated time span of less than a million years.

These stars would be the first to form at the beginning of the universe, during the Dark Ages. They would contain only hydrogen and helium and would be partially responsible for the genionization of the universe. These population III stars have long since ceased to exist in the universe. Some astronomers also believe that they are the source of very distant gamma-ray bursts.

Read also: The James Webb space telescope captures an impressive image of the Pillars of Creation

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