- 4350 - EARLIEST GALAXY AND QUASAR - Using the Hubble Space Telescope astronomers thought that disk galaxies were almost non-existent until the universe was about 6 billion years old, these new JWST results push the time these Milky Way–like galaxies form to almost the beginning of the universe.
----------------- 4350 - EARLIEST GALAXY AND QUASAR
- Astronomers are finding an abundance of
Milky Way–like galaxies in early universe, rewriting cosmic evolution theories.
-
- Galaxies from the early universe are more
like our own Milky Way than previously thought, flipping the entire narrative
of how scientists think about structure formation in the universe.
-
- Using the James Webb Space Telescope
(JWST), researchers discovered that
galaxies like our own Milky Way dominate throughout the universe and are
surprisingly common. These galaxies go
far back in the universe's history with many of these galaxies forming 10
billion years ago or longer.
-
- The Milky Way is a typical disk galaxy,
which has a shape similar to a pancake or compact disk, rotating about its
center and often containing spiral arms. These galaxies are thought to be the
most common in the nearby universe and might be the types of galaxies where
life can develop given the nature of their formation history.
-
- Astronomers previously considered that these
types of galaxies were too fragile to exist in the early universe when galaxy
mergers were more common, destroying what we thought was their delicate shapes. These disk galaxies are 10 times more common
than what astronomers believed based on previous observations with the Hubble
Space Telescope.
-
- For over 30 years it was thought that these
disk galaxies were rare in the early universe due to the common violent
encounters that galaxies undergo. This
"structure" in the universe forms much quicker than anyone had
anticipated.
-
- These JWST results show that disk galaxies
like our own Milky Way, are the most common type of galaxy in the universe.
This implies that most stars exist and form within these galaxies which is
changing our complete understanding of how galaxy formation occurs. These
results also suggest important questions about dark matter in the early
universe which we know very little about.
-
- The finding moves the astronomers one step
closer to finding out when galaxies first appeared in the universe, about
200-400 million years after the Big Bang.
-
- “Redshifts” in astronomy allows
astronomers to measure how far away distant objects are in the universe by
looking at how the colors change in the waves of light that they emit.
-
- If a light-emitting source is moving toward
us, the light is being 'squeezed,' and that shorter wavelength is represented
by blue light, or blueshift. But if that
source of light is moving away from us, the light it produces is being
'stretched,' and changes to a longer wavelength that is represented by red
light, or redshift.
-
- Edwin Hubble's discovery in the late 1920s
that our universe is ever-expanding is key to understanding how that galaxies
external to our Milky Way galaxy are moving away from us, and the more distant
they are, the faster they are moving away.
This relates to redshifts through the notion of distances. The higher the redshift an object is at,
such as a galaxy, the further away it is from us.
-
- The speed of light is finite, so it takes
time for light to travel over a distance to reach us. When we look at the sun, we aren't looking at
it what it looks like in the present, but rather what it looked like some eight
minutes ago. That's because that's how long it takes for the sun's radiation to
reach us. So, when we are looking at galaxies which are very far away, we are
looking at their images from a long time ago.
-
- The higher the redshift a galaxy is at, the
longer it takes for the light to reach us, so a higher redshift corresponds to
an earlier view of the universe. By
looking at galaxies at higher redshifts, we are getting earlier snapshots of
what the universe looked like a long time ago.
-
- The JWST was critical to this discovery
because objects in space like galaxies that are located at high redshifts, 11
and above, can only be detected by infrared light. This is beyond what NASA's Hubble Space
Telescope can detect because the Hubble telescope only sees from ultraviolet to
“near-infrared” light.
-
- JWST, the most powerful infrared telescope,
has the sensitivity and resolution for the job. Up until these first JWST data sets were
released in mid-July 2022, most
astronomers believed that the universe should have very few galaxies beyond
redshift 11.
-
- James Webb sees dozens of young Quasars in
the first billion years of the Universe.
Within almost every galaxy is a supermassive black hole. Millions,
sometimes billions of solar masses locked within an event horizon of space and
time. They can power luminous quasars, drive star formation, and change the
evolution of a galaxy. Because of their size and abundance, supermassive black
holes must have formed early in cosmic history.
-
- Since the luminosity of a black hole depends
in part on the size of the black hole, it can be used as a way to gauge the
mass of early supermassive black holes. Quasars are fairly common in the early
Universe.
-
- From these surveys, astronomers identified
350 compact galaxies with a redshift greater than z = 6. The light from these
galaxies began their journey to Earth when the Universe was less than a billion
years old, making them among the earliest galaxies.
-
- Of these, 64 of them appeared to have
quasars, indicating the presence of an active supermassive black hole.
Astronomers compared the luminosity and redshift to determine the age and mass
of the black holes.
-
- They found that statistically, these early
supermassive black holes were large compared to their galaxies, having a mass
of up to ten million solar masses, compared to a galactic mass of a few billion
Suns.
-
- This ratio is higher than that of the local
Universe, which suggests that the black holes form early when their galaxy is
small, rather than later when the galaxy is larger and more evolved. This
supports the direct collapse model of supermassive black holes rather than the
idea that they grow in mass through the merger of smaller black holes.
-
- More deep sky surveys are in the pipeline,
and with more data we will have more early black holes to study. Right now we
know of dozens of early supermassive black holes. As that grows to hundreds we
should be able to understand the various origins of galactic black holes.
-
-
February 10, 2023 EARLIEST GALAXY AND QUASAR 4350
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------ “Jim Detrick” -----------
--------------------- --- Monday, February 12,
2024
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