- 4577 - OLDEST GALAXIES - too old to make sense? - The James Webb Space Telescope found "tiny red dots" in the early universe representing overgrown supermassive black holes and stars that are impossibly old for the infant universe.
---------------------------- 4577
- OLDEST GALAXIES
- too old to make sense?
-
- These “odd red bodies” hide stars that
models suggest are "too old" to have lived during early cosmic times
and black holes that measure up to thousands of times larger than the
supermassive black hole at the heart of the Milky Way. Scientists believe these
objects must have been born in a way unique to the early universe by a method
that seems to have ceased after around 1 billion years of its existence.
-
- The three little red dots are seen as they
were when the universe was between 600 million and 800 million years old.
Though that may seem like a tremendously long time after the Big Bang, the fact
that the universe is 13.8 billion years old means it was no more than 5% of its
current age when these objects existed.
-
- This is very confusing. You can make this uncomfortably fit in our
current model of the universe, but only if we evoke some exotic, insanely rapid
formation at the beginning of time.
The researchers studied the
intensity of different wavelengths of light coming from the little red dots.
This revealed signs that the stars are hundreds of millions of years old. This is far older than is expected for stars
at this early stage of the universe.
-
- The researchers also saw traces of
supermassive black holes within the little red dots' regions with masses
equivalent to millions, sometimes even billions, of suns. These black holes are
between 100 and 1,000 times as massive as Sagittarius A* (Sgr A*), the
supermassive black hole at the heart of the Milky Way that sits just 26,000
light-years from Earth.
-
- Both of these discoveries are not expected
under current models of cosmic evolution, galaxy growth, or supermassive black
hole formation. All of these theories suggest galaxies and supermassive black
holes grow in lockstep, but this growth takes billions of years.
-
- They have also confirmed that these
galaxies appear to be packed with ancient stars, hundreds of millions of years
old, in a universe that is only 600 million to 800 million years old. These objects hold the record for the
earliest signatures of old starlight.
It was totally unexpected to find old stars in a very young universe.
These luminous objects do not quite fit comfortably into commology theories.
-
- They first spotted the little red dots while
using the JWST back in July, 2024. At the time, the researchers immediately
suspected the objects were actually galaxies that existed roughly 13.5 billion years ago. Deeper investigation of these objects' light
spectra confirmed these as galaxies that lived during the very dawn of time and
also revealed that "overgrown" supermassive black holes and
impossibly "old" stars were powering the red dots' impressive light
output.
-
- They are not certain how much of the light
from the little red dots comes from each of these sources. That means these
galaxies are either unexpectedly old and more massive than the Milky Way,
having formed far earlier than models predict, or have normal amounts of mass
yet overly massive black holes somehow.
These are voids that are vastly more massive than a similar galaxy would
have during the current epoch of the universe.
-
- Distinguishing between light from material
falling into a black hole and light emitted from stars in these tiny, distant
objects is challenging. That inability
to tell the difference in the current dataset leaves ample room for
interpretation of these intriguing object.
-
- All black holes have light-trapping
boundaries called "event horizons,", however much light they
contribute to the little red dots, must
come from the material that surrounds them rather than from within.
-
- The tremendous gravitational influence of
the black holes generates turbulent conditions in this material, which also
feeds the black hole over time, heating it and causing it to glow brightly.
Regions powered by supermassive black holes in this way are called
"quasars," and the regions of their galaxies they sit in are known as
"active galactic nuclei (AGNs).
-
- These newly found, "red dot" black
hole regions could be different from other quasars, even those the JWST has
already seen in the early universe. The
red dot black holes seem to produce far more ultraviolet light than expected.
Still, the most shocking thing about these supermassive black holes remains
just how massive they seem.
-
- Normally, supermassive black holes are
paired with galaxies. They grow up
together and go through all their major life experiences together. But here, we
have a fully formed adult black hole living inside of what should be a baby
galaxy.
-
- That doesn't really make sense because
these things should grow together, or at least that’s what we thought. The red dot galaxies themselves are also
surprising. They seem to be much smaller than other galaxies despite having
almost as many stars. That means the red dot galaxies seem to consist of
between 10 billion and 1 trillion stars crammed into a galaxy a few hundred
light-years across with a volume 1,000 times smaller than the Milky Way.
-
- If the Milky Way were reduced to the size of
one of these red dot galaxies, then the closest star to the sun (Proxima
Centauri, which is 4.2 light-years away) would be within the solar system.
Additionally, the distance between the Earth and the Milky Way's supermassive
black hole, Sgr A*, would be reduced from 26,000 light-years to just 26
light-years. That would see it and its surroundings appearing in the night sky
over Earth.
-
- These early galaxies would be so dense with
stars. These stars that must have formed
in a way we've never seen, under conditions we would never expect during a
period in which we’d never expect to see them. The universe stopped making objects like
these after just a couple of billion years. They are unique to the early
universe.
-
- Astronomers will be obtaining deeper spectra
by pointing the JWST at the red objects for prolonged periods of time to obtain
emission spectra of light associated with various elements. This could help
unravel the contributions of ancient stars and supermassive black holes in the
galaxies.
-
-
October 15, 2024 OLDEST
GALAXIES - too old to make sense? 4577
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--------------------- --- Tuesday, October 15,
2024
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