- 4365 - OLDEST GALAXY - is too massive to exist? - Astronomers believe the first galaxies formed around giant halos of dark matter. But a newly discovered galaxy dating to roughly 13 billion years ago mysteriously appeared long before that process should have occurred.
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4365 - OLDEST
GALAXY - is too massive to exist?
-
- The James Webb
Space Telescope (JWST) has found a galaxy in the early universe that's so
massive, it shouldn't exist, posing a "significant challenge" to the
standard model of cosmology.
-
- The galaxy, “ZF-UDS-7329”, contains more stars than the
Milky Way, despite having formed only 800 million years into the universe's
13.8 billion-year life span. This means they were somehow born without dark
matter seeding their formation, contrary to what the standard model of galaxy
formation suggests.
-
- How this could
have happened is unclear, but much like previous JWST discoveries of other
inexplicably massive galaxies in the early universe, it threatens to upend our
understanding of how the first matter in the universe formed, or possibly even
the standard model of cosmology itself.
-
- Massive dark
matter structures, which are thought to be necessary components for holding
early galaxies together, did not yet have time to form this early in the
universe.
-
- Light travels at a
fixed speed through the vacuum of space, so the deeper we look into the
universe, the more remote light we intercept and the further back in time we
see. JWST was used to spot ZF-UDS-7329
roughly 11.5 billion years in the past.
-
- By studying the
spectra of light coming from the stars of this extremely distant galaxy, the
researchers found that the stars were born 1.5 billion years prior to that
observation, or roughly 13 billion years ago.
-
- Astronomers aren't
certain when the very first globules of stars began to clump into the galaxies
we see today, but cosmologists previously estimated that the process began
slowly within the first few hundred million years after the Big Bang.
-
- Current theories
suggest that halos of dark matter (a mysterious and invisible substance
believed to make up 25% of the present universe) combined with gas to form the
first seedlings of galaxies. After 1 billion to 2 billion years of the universe's
life, the early protogalaxies then reached adolescence, forming into dwarf
galaxies that began devouring one another to grow into ones like our own.
-
- But this new
discovery has confounded this view: Not only did the galaxy crystallize without
enough built up dark matter to seed it, but not long after a sudden burst of
star formation, the galaxy abruptly became quiescent, meaning its star
formation ceased.
-
- This pushes the
boundaries of our current understanding of how galaxies form and evolve. How did they form so fast very early in the
universe, and what mysterious mechanisms lead to stopping them forming stars
abruptly when the rest of the universe is doing so.
-
- When the universe
was just two billion years old, the newfound spiral galaxy,
“ceers-2112”, appears to have featured a bar of stars and gas
cutting across its heart. The Milky
Way, also a spiral galaxy, sports a similar bar. Scientists suspect the Milky
Way's bar rotates cylindrically, like a toilet roll holder does as you unravel
toilet paper, funneling gas into the galaxy's center and sparking bursts of
star formation.
-
- Astronomers
previously thought this galactic structure marks the end of a galaxy's
formative years, so it was expected to be seen only in old galaxies that may
have reached full maturity, those that existed halfway through the evolution of
the universe.
-
- However, the new
findings conclude it may not be necessarily true that barred spirals must've
roamed the universe for so long. The discovery of spiral galaxy ceers-2112
reveals galaxies that resemble our own already existed 11.7 billion years ago,
when the universe had just 15 percent of its life.
-
- The JWST can
collect six times more light than Hubble, allowing for more detailed features
of faraway galaxies to come into view. Ceers-2112 is observed at a redshift of
3, when the universe was 2,100 million years old.
-
- This means the
light from the galaxy took 11.7 billion years to reach the JWST. As the galactic bars are seen in roughly
two-thirds of all spiral galaxies, but bars are thought to have manifested
about 4 billion years into the birth of the universe.
-
- Studying faraway
galaxies are essential to understand their history, opening the door to new
scenarios about galaxy formation and evolution. Theoretical predictions from cosmological
simulations really struggle to reproduce such systems at those epochs. We now
need to understand which key physical ingredient is missing in our models, if
something is missing.
-
- Astronomers think
85 percent of all matter in the universe is “dark matter”, a mysterious
substance elusive to telescopic observations because it doesn't interact with
light at all. Dark matter is thought to have radically influenced galaxy
evolution and star formation from as early as 380,000 years after the Big Bang.
-
- Findings from the
new study show galaxy evolution, at least in the case of ceers-2112, was
dominated by ordinary matter and not dark matter when the universe was about
two billion years old. The galaxy's morphology shows that the contribution of
dark matter in the galactic bar of ceers-2112 is very low and is instead
dominated by normal matter.
-
- This discovery
confirms that the evolution of this galaxy was dominated by baryons, the
ordinary matter we are made of, and not by dark matter, despite its
over-abundance, when the universe had only 15% of its actual age.
-
- JWST, in just one
year of observations, is revolutionizing our understanding of the early
universe.
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-
February 24, 2024
OLDEST GALAXY
- is too massive to exist? 4365
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