Astrophysicists confirm the faintest galaxy ever seen in the early
universe
The small, distant galaxy JD1 is typical of the kind that burned through hydrogen left over from the Big Bang

Date:
June 1, 2023
Source:
University of California - Los Angeles
Summary:
After the Big Bang, the universe expanded and cooled sufficiently
for hydrogen atoms to form. In the absence of light from the first
stars and galaxies, the universe entered a period known as the
cosmic dark ages.

The first stars and galaxies appeared several hundred million
years later and began burning away the hydrogen fog left over
from the Big Bang, rendering the universe transparent, like it is
today. Researchers have now confirmed the existence of a distant,
faint galaxy typical of those whose light burned through the
hydrogen atoms; the finding should help them understand how the
cosmic dark ages ended.


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==========================================================================
FULL STORY ========================================================================== After the Big Bang, the universe expanded and cooled sufficiently for
hydrogen atoms to form. In the absence of light from the first stars
and galaxies, the universe entered a period known as the cosmic dark ages.

The first stars and galaxies appeared several hundred million years later
and began burning away the hydrogen fog left over from the Big Bang,
rendering the universe transparent, like it is today.

Researchers led by astrophysicists from UCLA confirmed the existence of
a distant, faint galaxy typical of those whose light burned through the hydrogen atoms; the finding should help them understand how the cosmic
dark ages ended.

An international research team led by UCLA astrophysicists has confirmed
the existence of the faintest galaxy ever seen in the early universe. The galaxy, called JD1, is one of the most distant identified to date, and
it is typical of the kinds of galaxies that burned through the fog of
hydrogen atoms left over from the Big Bang, letting light shine through
the universe and shaping it into what exists today.

The discovery was made using NASA's James Webb Space Telescope, and the findings are published in the journal Nature.

The first billion years of the universe's life were a crucial period
in its evolution. After the Big Bang, approximately 13.8 billion years
ago, the universe expanded and cooled sufficiently for hydrogen atoms
to form. Hydrogen atoms absorb ultraviolet photons from young stars;
however, until the birth of the first stars and galaxies, the universe
became dark and entered a period known as the cosmic dark ages. The
appearance of the first stars and galaxies a few hundred million years
later bathed the universe in energetic ultraviolet light which began
burning, or ionizing, the hydrogen fog. That, in turn, enabled photons
to travel through space, rendering the universe transparent.

Determining the types of galaxies that dominated that era -- dubbed the
Epoch of Reionization -- is a major goal in astronomy today, but until
the development of the Webb telescope, scientists lacked the sensitive
infrared instruments required to study the first generation of galaxies.

"Most of the galaxies found with JWST so far are bright galaxies that
are rare and not thought to be particularly representative of the young galaxies that populated the early universe," said Guido Roberts-Borsani,
a UCLA postdoctoral researcher and the study's first author. "As such,
while important, they are not thought to be the main agents that burned
through all of that hydrogen fog.

"Ultra-faint galaxies such as JD1, on the other hand, are far more
numerous, which is why we believe they are more representative of the
galaxies that conducted the reionization process, allowing ultraviolet
light to travel unimpeded through space and time." JD1 is so dim and so
far away that it is challenging to study without a powerful telescope --
and a helping hand from nature. JD1 is located behind a large cluster
of nearby galaxies, called Abell 2744, whose combined gravitational
strength bends and amplifies the light from JD1, making it appear larger
and 13 times brighter than it otherwise would. The effect, known as gravitational lensing, is similar to how a magnifying glass distorts and amplifies light within its field of view; without gravitational lensing,
JD1 would likely have been missed.

The researchers used the Webb Telescope's near-infrared spectrograph instrument, NIRSpec, to obtain an infrared light spectrum of the galaxy, allowing them to determine its precise age and its distance from Earth,
as well as the number of stars and amount of dust and heavy elements
that it formed in its relatively short lifetime.

The combination of the galaxy's gravitational magnification and new images
from another one of the Webb Telescope's near-infrared instruments,
NIRCam, also made it possible for the team to study the galaxy's
structure in unprecedented detail and resolution, revealing three main elongated clumps of dust and gas that are forming stars. The team used
the new data to trace JD1's light back to its original source and shape, revealing a compact galaxy just a fraction of the size of older galaxies
like the Milky Way, which is 13.6 billion years old.

Because light takes time to travel to Earth, JD1 is seen as it was approximately 13.3 billion years ago, when the universe was only about 4%
of its present age.

"Before the Webb telescope switched on, just a year ago, we could not
even dream of confirming such a faint galaxy," said Tommaso Treu, a UCLA physics and astronomy professor, and the study's second author. "The combination of JWST and the magnifying power of gravitational lensing
is a revolution. We are rewriting the book on how galaxies formed and
evolved in the immediate aftermath of the Big Bang."
* RELATED_TOPICS
o Space_&_Time
# Astrophysics # Galaxies # Big_Bang # Cosmology #
Astronomy # NASA # Space_Telescopes # Stars
* RELATED_TERMS
o Galaxy_formation_and_evolution o Big_Bang_nucleosynthesis o
Big_Bang o Cosmic_microwave_background_radiation o Dark_matter
o Atom o Galaxy o Large-scale_structure_of_the_cosmos

========================================================================== Story Source: Materials provided by
University_of_California_-_Los_Angeles. Original written by Holly
Ober. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Guido Roberts-Borsani, Tommaso Treu, Wenlei Chen, Takahiro
Morishita,
Eros Vanzella, Adi Zitrin, Pietro Bergamini, Marco Castellano,
Adriano Fontana, Karl Glazebrook, Claudio Grillo, Patrick L. Kelly,
Emiliano Merlin, Themiya Nanayakkara, Diego Paris, Piero Rosati,
Lilan Yang, Ana Acebron, Andrea Bonchi, Kit Boyett, Marusa
Bradač, Gabriel Brammer, Tom Broadhurst, Antonello Calabro',
Jose M. Diego, Alan Dressler, Lukas J. Furtak, Alexei V. Filippenko,
Alaina Henry, Anton M. Koekemoer, Nicha Leethochawalit, Matthew
A. Malkan, Charlotte Mason, Amata Mercurio, Benjamin Metha,
Laura Pentericci, Justin Pierel, Steven Rieck, Namrata Roy, Paola
Santini, Victoria Strait, Robert Strausbaugh, Michele Trenti,
Benedetta Vulcani, Lifan Wang, Xin Wang, Rogier A. Windhorst. The
nature of an ultra-faint galaxy in the cosmic dark ages seen with
JWST. Nature, 2023; DOI: 10.1038/s41586-023-05994-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230601155742.htm

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