- 4372 - WEBB FINDS - earliest galaxies. - 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.
------------------- 4372 - WEBB FINDS - earliest galaxies
- 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. The Universe began just 13.8 billion years
ago.
-
- The new 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.
-
- Having these
extremely massive galaxies so early in the universe is posing significant
challenges to our standard model of cosmology because 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. This is what enabled the researchers to use JWST to spot
“ZF-UDS-7329” 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 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, which is 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 proto-galaxies then reached adolescence, forming
into dwarf galaxies that began devouring one another to grow into ones like our
own.
-
- But the 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. The key question now is how 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.
-
- Astronomers also
have discovered the most distant example of a galaxy in the universe that looks
like our home galaxy, the Milky Way.
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, like a slash across a no-smoking sign.
-
- 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, perhaps those that existed halfway through the
evolution of the universe. The Hubble
Space Telescope's past observations have shown the early universe hosted very
few barred galaxies.
-
- 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 us.
-
- This is a
surprising find, 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.
-
- 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.
-
- Studies like these
are also shaping our understanding of the role dark matter played in the early
universe. 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.
-
- 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.
-
- These are the
first spectroscopic observations of the faintest galaxies during the first
billion years of the universe. What
sources caused the reionization of the universe? These new results have
effectively demonstrated that small dwarf galaxies are the likely producers of
prodigious amounts of this energetic radiation.
-
- Reionization era was
a period of darkness without any stars or galaxies, filled with a dense fog of hydrogen
gas until the first stars ionized the gas around them, and light began to
travel through. Astronomers have spent decades trying to identify the sources
that emitted radiation powerful enough to gradually clear away this hydrogen
fog that blanketed the early universe.
-
- Gravitational
lensing magnifies and distorts the appearance of distant galaxies, so they look
very different from those in the foreground. The galaxy cluster 'lens' is so
massive that it warps the fabric of space itself, so much so that light from
distant galaxies that passes through the warped space also takes on a warped
appearance.
-
- This magnification
effect allowed the team to study very distant sources of light beyond “Abell
2744”, revealing eight extremely faint galaxies that would otherwise be
undetectable, even to Webb.
-
- These faint
galaxies are immense producers of ionizing radiation, at levels that are four
times larger than what was previously assumed. This means that most of the
photons that reionized the universe likely came from these dwarf galaxies.
-
- This discovery
unveils the crucial role played by ultra-faint galaxies in the early universe's
evolution. They produce ionizing photons
that transform neutral hydrogen into ionized plasma during cosmic reionization.
-
- Despite their tiny
size, these low-mass galaxies are prolific producers of energetic radiation,
and their abundance during this period is so substantial that their collective
influence can transform the entire state of the universe.
-
- To arrive at this
conclusion, the team first combined ultra-deep Webb imaging data with ancillary
imaging of Abell 2744 from the Hubble Space Telescope in order to select
extremely faint galaxy candidates in the epoch of reionization. This was
followed by spectroscopy with Webb's Near-InfraRed Spectrograph (NIRSpec). The
instrument's Multi-Shutter Assembly was used to obtain multi-object
spectroscopy of these faint galaxies.
-
- This is the first
time scientists have robustly measured the number density of these faint
galaxies, and they have successfully confirmed that they are the most abundant
population during the epoch of reionization. This also marks the first time
that the ionizing power of these galaxies has been measured, enabling
astronomers to determine that they are producing sufficient energetic radiation
to ionize the early universe.
-
- The incredible
sensitivity of NIRSpec combined with the gravitational amplification provided
by Abell 2744 enabled them to identify and study these galaxies from the first
billion years of the universe in detail, despite their being over 100 times
fainter than our own Milky Way.
-
- In an upcoming
Webb observing program, termed “GLIMPSE”, scientists will obtain the deepest
observations ever on the sky. By targeting another galaxy cluster, “Abell
S1063”, even fainter galaxies during the epoch of reionization will be
identified in order to verify whether this population is representative of the
large-scale distribution of galaxies.
-
- The GLIMPSE
observations will also help astronomers probe the period known as “Cosmic
Dawn”, when the universe was only a few million years old, to develop our
understanding of the emergence of the first galaxies.
-
- Now, let's look at
the closest galaxy with mid-infrared observations of nearby supernova “SN
1987A”. Supernovae are powerful and
luminous stellar explosions that could help us better understand the evolution
of stars and galaxies. Astronomers divide supernovae into two groups based on
their atomic spectra: Type I and Type II. Type I Supernovae lack hydrogen in
their spectra, while those of Type II
showcase spectral lines of hydrogen.
-
- “SN 1987A”, which
occurred about 168,000 light years away in the Large Magellanic Cloud (LMC),
was first spotted in late February 1987. It was the closest visible supernova
in almost 400 years, since Kepler's Supernova, observed in 1604.
-
- Previous studies
have found that SN 1987A was a Type II Supernovae that brightened rapidly and
reached an apparent magnitude of about 3.0. Due to its proximity, the supernova
has been a subject of many observations following its evolution, imaging its
process of transformation into a supernova remnant.
-
-
February 28, 2024
WEBB FINDS -
earliest galaxies 4372
------------------------------------------------------------------------------------------
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Thursday, February 29, 2024 ---------------------------------
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