- 4591 -
JAMES WEBB -
discoveries are surprises? - Prior to the James Webb Telescope, JWST,
our best observations plus our leading theories had combined to create a
“consensus” picture of the Universe, showing us the broad strokes of how our
cosmos grew up and gave rise to us. Since July, 2022, however, when JWST’s
science operations began, we’ve learned an incredible amount of new information
about the Universe, from star and planet formation to the earliest galaxies.
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- JAMES WEBB - discoveries are surprises?
- JWST
began its science operations in July, 2022. Back then, we had an
incredible amount of information about our Universe that we had already
uncovered, as well as a great number of cosmic puzzles we were still facing
with no obvious solution in sight.
-
- We knew that our Universe was 13.8 billion
years old, began with a hot Big Bang in the aftermath of an inflationary
period, was dominated by the mysterious dark energy and dark matter, whose
nature was unknown, with the big problem of the “Hubble tension” looming over
our measurement of the expansion rate,where supermassive black holes were
spotted to be very massive even early on,and where even the earliest galaxies
detected were massive, somewhat evolved, and bright.
-
- Our picture of the Universe included
galactic, stellar, and chemical evolution, from a pristine early state to the
late-time state that mirrors what we observe nearby. It included a history
where more than two sextillion stars, locked up in trillions upon trillions of
galaxies, were spread all throughout an observable Universe that spans 92
billion light-years in diameter.
-
- But many big questions still remained. What
are dark matter and dark energy? How fast is our Universe actually expanding?
When did the first stars and galaxies form? How did supermassive black holes
arise? And how did stars like our Sun and planets like our Earth take shape and
form?
-
- JWST has shown us the most distant galaxies
in the Universe ever discovered. If we assign 3D positions to the galaxies that
have been sufficiently observed-and-measured, we can construct a visualized
fly-through of the Universe, as the “CEERS” data from JWST enables us to do. At
greater distances, compact, star-forming galaxies are more common; at closer
distances, more diffuse, quiescent galaxies are the norm.
-
- JWST also has several important
limitations. It has a narrow
field-of-view, so it can’t observe very much of the Universe at once. It’s incredibly oversubscribed, with about
ten high-quality proposals for observing rejected for every one that’s
accepted. It takes much longer to
perform spectroscopy on an object than it does to conduct imaging, severely
limiting how many objects can be spectroscopically analyzed.
-
- And, it can’t image objects in multiple
filters simultaneously; the greater the number of sets of wavelengths you want
to perform photometric imaging at, the longer you need to observe with JWST.
-
- Even with these restrictions and
limitations, there’s a tremendous amount of novel science that JWST is uniquely
equipped to conduct. JWST was expected
to break cosmic records such as the “most distant” or “earliest” example of
certain classes of objects, as JWST was designed with those goals in mind.
However, there were a whole suite of new discoveries that were both unexpected
and suddenly possible thanks to JWST’s capabilities.
-
- JWST has these novel capabilities enabled
by new technologies, a large primary mirror in space owing to its segmented and
folding nature, extremely cold temperatures owing to a 5-layer sunshield, pristine optics and
instruments owing to advances in instrumentation and clean room technology.
-
- But the second set of reasons is profound
not just for JWST, but in so much of physics and astronomy in general. Whenever
you build an instrument, observatory, or machine that: surpasses all previous
limits of all similar endeavors, particularly over the specific range of
parameters that similar endeavors were sensitive to in the past,nand where you
then use that instrument, observatory, or machine to look in new locations or
even to look at objects or phenomena that you’ve looked at previously, those new
capabilities enable something that simply isn’t possible without them: the
possibility of discovering something new simply by looking with this new tool.
-
- With longer-wavelength and
higher-resolution capabilities than Hubble, Spitzer, SOFIA, or any of the
world-class ground-based optical and infrared observatories in our arsenal,
ultra-distant stars, quasars, and galaxies were exactly the types of objects
that JWST was designed to detect. There are many examples of cosmic distance
records that have been broken and revised since the JWST era began in 2022.
-
- JWST is a “cosmic time machine” with
ability to see back farther into our cosmic past than any other optical or
infrared observatory in history. We
can see the Big Bang’s leftover glow with microwave light, and we can
potentially see the signature of neutral hydrogen atoms even before the
formation of stars with far-infrared and radio astronomy thanks to the 21cm
spin-flip transition of hydrogen.
-
- The nature of this record-breakingly
distant object could be determined because its light comes to us from when the
Universe was only 285-290 million years old: just 2.1% of its current age.
“JADES-GS-z14-1”, just below it, comes from when the Universe was ~300 million
years old. Compared to large, modern-day galaxies, all early galaxies contain a
paucity of stars and have irregular, ill-defined shapes.
-
- Prior to JWST the most distant galaxy in
the known Universe was “GN-z11”, which was observed by the Hubble Space
Telescope and which set the cosmic distance record back in 2016. When JWST
began science operations in 2022, it was still the most distant confirmed
galaxy known to humanity.
-
- As of late 2024, however, not only is
GN-z11 no longer the record-holder, but it isn’t even in the top 10. All ten of
the most distant galaxies were discovered or had key features detected by JWST
that confirmed their great distance.
-
- The JADES collaboration has spotted and
confirmed the current cosmic record-holder: JADES-GS-z14-0. This ultra-distant galaxy is truly
remarkable in a number of ways.
Its light comes to us from
just 285 million years after the Big Bang, when the Universe was 2.1% of its
current age.
-
- It overlaps with a brighter foreground
galaxy, but thanks to JWST’s incredible resolution, we can disentangle the two
galaxies, revealing the more distant background object in detail.
It has a redshift of 14.32,
meaning that the light we’re observing has been stretched by an additional
1432% of its originally emitted wavelength by the time JWST observes it.
-
- This galaxy was bright: not only brighter
than our leading theories would predict, but substantially brighter than even
previously-observed ultra-distant JWST galaxies. And, there’s extremely little
dust in this galaxy: again something that defies predictions.
-
- JWST has also broken many other cosmic
distance records. It discovered the earliest proto-cluster of galaxies ever
seen, by finding seven independent galaxies in the same narrowly-confined
region of the sky that are all at the precise same redshift: 7.88,
corresponding to an epoch just 650 million years after the Big Bang.
-
- This proto-cluster of galaxies, known as
“A2744z7p9OD”, broke the old record by an impressive 150 million years.
Moreover, instead of just appearing as single, red dots that were
indistinguishable from individual point-like sources, many of these early
galaxies appear to be extended objects, and some may even exhibit signatures of
having satellite companions.
-
- Hundreds of ultra-distant galaxy candidates
— including dozens that may yet break JWST’s newly set records — have also been
found in this early JWST data. The most distant gravitational lens ever
discovered was found with JWST by pure serendipity in a 2023 study. -
-
- Many of the most distant supermassive black
holes of all time (including the four most distant of all) have been found
thanks to JWST as well, including a remarkable one in the galaxy UHZ1: where
JWST (in infrared light) and Chandra (in X-ray light) teamed up to find a
supermassive black hole of approximately double the mass of the one at the
Milky Way’s center, but where only about ~10 million solar masses worth of
stars are found in that galaxy.
-
- Although it’s no surprise that JWST could
reveal these objects, the mass ratios between the black hole and the total
number of stars in galaxies such as this were wildly unexpected.
-
- JWST looked at the Crab Nebula, a supernova
remnant that was born with the core-collapse of a massive star nearly a
thousand years ago, back in 1054. In the 970 years since, the Crab Nebula has
expanded and grown to be some 11 light-years across, showcasing the power of a
supernova explosion even a millennium later. With its sensitivity to features
very difficult to resolve with prior observatories, it may yet resolve the mass
mystery: why the central pulsar plus the material in the supernova ejecta doesn’t
add up to the minimum mass (of 8 solar masses) thought necessary to trigger a
core-collapse supernova.
-
- It peered inside the Orion Nebula, which is
the closest large star-forming region to Earth. Inside, it sought to better
image protostars along with mapping out the neutral matter and dust inside of
it. It found something that was wholly
unexpected with its infrared-sensitive capabilities: an enormous number of
Jupiter-mass (and super-Jupiter mass) planets that were freely floating inside
these star-forming regions, planets without parent stars of any type.
-
- Not only was the discovery of these planets
a surprise, but a whopping 9% of them were found being bound together in binary
pairs, making them Jupiter-Mass Binary Objects (JuMBOs), a class of object not
even known to exist prior to JWST.
-
- When JWST peered inside the well-studied El
Gordo galaxy cluster, it found some spectacularly-shaped gravitational lenses,
which is precisely what you’d expect to find in a large, massive, but distant
galaxy cluster whose gravity can curve and distort the spacetime it occupies.
-
- As a result, background objects are lensed:
distorted, stretched, and magnified, often appearing as multiple images at
once. Also found in that field, however, was something never seen before: a
single red supergiant star located at cosmological distances, only visible to
JWST because of the combination of its capabilities along with the lensing
properties of the El Gordo galaxy cluster. Known as “Quyllur” it’s located more
than 10 billion light-years away.
-
- JWST also observed a large number of
relatively nearby galaxies that had three important properties: they were rich in Cepheid variable stars,
which is a special type of star that varies in brightness over time with a
well-known relationship, they were found
in galaxies that also housed, at one point, at least one type Ia supernova,
making them important “connecting rungs” in the cosmic distance ladder method
of measuring the expansion rate of the Universe.
-
- Perhaps the single most surprising JWST
discovery came from looking at the bright, nearby star Fomalhaut: one of the
top 20 brightest stars in the night sky, and one that’s located only ~25
light-years away. It’s also a very young stellar system: so young that it still
has a dust-rich debris disk surrounding it: something that hasn’t been true of
our own Solar System in nearly four billion years.
-
- There were hints that there might be an
exoplanet in this system, and JWST time was allocated to a team that wanted to
search for it. With its high resolution capabilities and sensitivity to
long-wavelength infrared light, there was a chance that JWST could have
directly imaged such a world.
-
- The story that the observations wound up
telling was a completely unexpected one. Seeking a potential planet, JWST
instead found:an inner disk, corresponding to the inner planets and an
asteroid-like belt, an outer ring,
previously seen by Hubble and ALMA, corresponding to a Kuiper-like belt, an inner gap and an outer gap in these
features, corresponding to the location of likely (although invisible to JWST’s
eyes) exoplanets, and: an intermediate
belt, something with no analogue in our own Solar System.
-
- A wide variety of telescopes have looked
at the Fomalhaut system in a variety of wavelengths from both the ground and in
space. Only JWST, so far, has been able to resolve the inner regions of the
dusty debris present in the Fomalhaut system. Whereas Herschel, Hubble, and
ALMA data all point to a picture with an inner disk and an outer belt, JWST’s
capabilities reveal an “intermediate” belt in between the two. Unlike our Solar
System, which has only the asteroid and Kuiper belts, this find was a total
surprise.
-
- JWST has broken the cosmic distance records
in many regards: for most distant galaxy, most distant galaxy cluster, most
distant red supergiant, most distant gravitational lens, and most distant
supermassive black hole, among several others. But what it’s taught us about
the Universe have included surprises that no one could have anticipated prior
to JWST unleashing the power of its discovery potential onto humanity.
-
- Do stellar systems, like our own Solar
System, have two belts, three belts, or some other number of belts in general,
and which configuration is most common? (We didn’t know to ask this question
before JWST.)
-
- What types of non-stellar systems are
birthed when stars form, and are super-Jupiter planets and systems with
Jupiter-mass binary objects in them just the tip of the iceberg? (We didn’t
know that JuMBOs existed prior to JWST.)
-
- How do supermassive black holes truly form
in the Universe, and do these JWST findings rule out the possibility that they
arose from the first generations of stars?
The answer seems to be “yes,” incredibly!
-
- Now that field-crowding of Cepheids has been
ruled out as the cause of the Hubble tension, what is its ultimate
resolution? Still an open question, but
one potential contaminant has been eliminated.
-
- And, despite their initially surprising
abundances and brightnesses, are the earliest galaxies seen by JWST truly
consistent with our consensus picture of the Universe? The answer again appears to be “yes,” as
those properties of galaxies are mostly attributable to bursty star formation
and the enhancement of light from supermassive black hole activity.
-
- JWST has taught us an incredible amount of
information about the Universe already, including what it’s like, how it grew
up, and how it created stellar and planetary systems both different to as well
as similar to our own.
-
- With another 20 years of science operations
to look forward to, the only thing we can be certain of is that the records
JWST has set, as well as the science questions it’s raised and begun to answer,
are a harbinger of a great many discoveries still to come.
-
October 31, 2024 JAMES WEBB
- discoveries are surprises? 4583
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------ “Jim Detrick” -----------
--------------------- --- Thursday, October 31,
2024
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