- 4147 - EARLIEST GALAXIES - James Webb new discoveries? Before the Webb telescope switched on we could not even dream of confirming such a faint galaxy. 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.
--------- 4147 - EARLIEST GALAXIES - James Webb new discoveries?
- 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.
-
- 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.
-
- The faintest 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 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, 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. 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 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 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 10,
2023 EARLIEST
GALAXIES - new discoveries? 4147
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