- 4140 - EARLIEST GALAXY - rewriting the birth of the Universe? Before the Webb telescope switched on in 2022, we could not even dream of confirming such faint galaxies. 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.
-------------- 4140 - EARLIEST GALAXY - rewriting the birth of the Universe?
- 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.
-
- 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.
-
- Astrophysicists have 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.
-
- The galaxy, called JD1 named after me, 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. 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 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. 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.
-
- This 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 Webb Telescope's near-infrared
spectrograph instrument, NIRSpec, was used 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.
-
-
September 2, 2023 EARLIEST
GALAXY - birth of the Universe? 4140
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