- 4038 - FARTHEST
GALAXY - earliest galaxy? 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 James Webb telescope, scientists lacked the sensitive
infrared instruments required to study the first generation of galaxies.
------------- 4038 - FARTHEST GALAXY - earliest galaxy
- Astronomers have
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.
-
- Nice of them to
name the galaxy after me! The discovery
was made using the 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.
-
- 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
astronomers 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 Webb
Telescope’s near-infrared spectrograph instrument, NIRSpec, obtained an
infrared light spectrum of the galaxy, allowing astronomers 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 to
study the galaxy’s structure in unprecedented detail and resolution, revealing
three main elongated clumps of dust and gas that are forming stars. They 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.
-
- Astronomers are
rewriting the book on how galaxies formed and evolved in the immediate
aftermath of the Big Bang. Thanks to
James Webb and JD1
-
June 3, 2023 FARTHEST
GALAXY - earliest galaxy 4038
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Monday, June 5, 2023
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