The James Webb Space Telescope (JWST) is the most complex and powerful space observatory ever deployed. What it has discovered since it commenced operations has been nothing short of groundbreaking!
Host | Matthew S Williams
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Episode Notes
The James Webb Space Telescope (JWST) is the most complex and powerful space observatory ever deployed. What it has discovered since it commenced operations has been nothing short of groundbreaking! However, many of these discoveries were unexpected and confounded astronomers. But this is the purpose of Webb, which is designed to investigate the biggest questions we have about the nature of the Universe.
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What Discoveries has the James Webb Space Telescope Made So Far? | Stories From Space Podcast With Matthew S Williams
Episode 96 - the JWST
[00:00:00] The authors acknowledge that this podcast was recorded on the
traditional unceded lands of the Lekwungen peoples. Hello, and welcome back
to another episode of Stories from Space. I'm your host, Matt Williams. And
today, after much waiting, we're going to be looking at the breakthroughs,
discoveries, and unexpected finds brought to us courtesy of the James Webb
Space Telescope, the next generation observatory created by NASA, the
European Space Agency, and the Canadian Space Agency.
The mission launched on December 25th, 2021, on Christmas Day, no less.
Quite the present. And this represented the culmination of decades of planning
and preparation, which began in 1996. At the time, the telescope was
codenamed the Next Generation Space Telescope. And after multiple delays
and cost overruns due to the sheer complexity of the design, it [00:01:00] finally
made it to space and began capturing the clearest and most detailed images of
the universe ever seen.
The mission has been identified as a successor to the Hubble Space Telescope.
given that it was designed to view objects that were either too old, too distant,
or too faint for the venerable Hubble. In addition, Webb is the designated
successor to the Spitzer Space Telescope, an infrared telescope that spent years
observing the unseen universe, which is to say the parts of the universe that
cannot be viewed in visible light because they're obscured by dust, gas, or
brighter objects, or simply too faint.
And with its sophisticated mirror and an advanced suite of instruments,
astronomers expected that it would be able to make many investigations across
multiple fields of astronomy and cosmology, which would include the first
galaxies in the universe, forming less than 1 billion years before the Big Bang.
Studies of [00:02:00] red dwarf suns and brown dwarfs, as well as planet
forming debris disks, much like Spitzer. And also, the detailed characterization
of exoplanets. Specifically, characterization of their atmospheres to determine if
they could in fact be habitable. All of this was made possible by a complex,
gold coated beryllium primary mirror, made up of 18 separate hexagonal
mirrors.
Add to that a sunshield that prevents the Webb telescope from being overheated
by any external heat sources, which would throw off its infrared sensors, and its
origami like design, which allows it to fold up so it's small enough to fit into thepayload fairing of a rocket, and then deploy in space, and you've got the most
powerful, sensitive, and complex observatory ever deployed.
So, what has Webb accomplished since it was deployed roughly three and a half
years ago? The list is long, but a few things stand [00:03:00] out above the rest.
For instance, the discoveries made by Webb have led astronomers and
cosmologists to rethink a lot of their previously held notions. This is precisely
what Webb was intended to do.
By viewing the earliest galaxies in the universe, astronomers hope to get a better
idea of everything that occurred during the early universe that led to the
universe evolving into what we see today. In addition, Webb was intended to
make accurate distance measurements of the most distant observable objects in
our universe in the hopes of resolving a major issue.
It has plagued astronomers since the 1990s, which was originally discovered by
the Hubble Telescope. And this is known as the Hubble Tension. To break that
down, first we need to talk about how astronomers measure cosmic distances,
which requires several different methods, collectively known as the
Cosmological Distance Ladder.
The purpose of these distance [00:04:00] measurements is to determine the rate
at which the cosmos is expanding. As noted in previous episodes, this is known
as the Hubble Lemaître constant, named after Edwin Hubble and Georges
Lemaître, the two astrophysicists who first noted that the universe was in a state
of expansion back in the 1920s and 30s.
Prior to the 1990s, astronomers were able to get a clear view and distance
measurements for objects up to 4 billion light years away. But with the
deployment of Hubble, that all changed. Initially, Hubble was able to study
objects up to 10 billion light years away. But as time went on, and with the
Hubble Deep Fields Astronomers realized that the rate of cosmic expansion was
getting faster over time.
As a result of this, obtaining accurate measurements of distant objects became
absolutely crucial. And for this, astronomers rely on the cosmological distance
ladder. As indicated [00:05:00] in our episode about the Hubble Tension, this
ladder consists of several rungs, each of which involves a different method and
a different standard candle, or bright object, to gauge the distance of objects that
are farther and farther away from the solar system.For local distances, astronomers use parallax measurements, a technique that
has been used since classical antiquity to determine the distance of planets. But
in modern astronomy, This technique consists of observing stars that vary in
brightness, otherwise known as variable stars. And when viewing Cepheid
variables from different points in Earth's orbit, astronomers are able to
determine the distance to objects that are between 000 light years away.
The next rung of the ladder consists of parallax measurements for Cepheid
variables and RR Lyrae variables, an even brighter class of star. These two
techniques combined allow astronomers to gauge the distances [00:06:00] of
local objects within our galaxy, as well as local galaxies, the closest neighbors
of the Milky Way.
But for the next rung of the ladder, measuring distances up to 1 billion light
years away, astronomers require a much brighter standard candle, to which they
turn to Type Ia supernovas. A Type Ia is a type of supernova that occurs in
binary systems, where one star is a white dwarf, and the other can be anything
from a massive star to a smaller white dwarf.
The powerful gravity of the white dwarf star will gradually siphon material
from the other star, eventually reaching a critical mass, at which point it will
ignite and trigger a supernova explosion. Beyond distances of 1 billion light
years, astronomers must rely on redshift measurements. Essentially, redshift
describes how, due to the expansion of the universe, light coming from distant
sources is shifted [00:07:00] towards the red end of the spectrum.
To put it another way, The wavelength of a light is elongated by the expansion
of spacetime itself. And since longer wavelengths correspond to light that is
closer to the red end of the spectrum, you get redshift. Therefore, the farther the
object is away from Earth, the longer the elongation. And as noted, before the
1990s, observations and redshift measurements were restricted to objects within
4 billion light years.
Hubble managed to change all that by measuring redshift as some of the most
distant observable objects, objects that were up to 13 billion light years away.
And given that astronomers, when looking through distant space, are also
looking back in time, this meant that these were the first galaxies in the universe
that had emerged from the so called Dark Ages about 13 billion years ago.
And this was accompanied by measurements of the cosmic microwave
[00:08:00] background, by NASA's cosmic Background Explorer, or COBE,
and the European Space Agency's Planck mission. As noted before, the CMBrefers to the relic radiation emitted shortly after the Big Bang, when neutral
hydrogen atoms finished forming, allowing for the free propagation of photons.
Given the immense distance that this light has crossed in order to reach us
today, it has been redshifted to the point that it is no longer in the visible
spectrum and can be seen only in the microwave wavelength. By measuring the
redshift of the CMB, astronomers were finally able to constrain the age of the
universe at roughly 13.
8 billion years. However, when comparing distance measurements on different
rungs of the ladder, they noticed a discrepancy. Essentially, the CMB
measurements indicated that the Hubble constant was about [00:09:00] 68
kilometers per second per megaparsec. In other words, for every million
parsecs, the universe is expanding at a rate of 68 kilometers every second.
However, measurements of the local universe and local galaxies produced a
value of 74 kilometers per second per megaparsec. This came to be known as
the Hubble tension. For decades, astronomers looked forward to the day when
the next generation space telescope that would become Webb would be
deployed to space, would make its own measurements of the distant galaxies in
the universe, and hopefully resolve this tension by bringing all the values into
harmony.
However, Webb's observations confirmed Hubble's original observations,
producing the same measurements that were in tension. In an attempt to explain
this, astronomers and astrophysicists have been working on various theories.
Currently, a leading contender is the idea of early dark energy, which would,
according to theory, produce [00:10:00] a burst of extra, unexpected expansion
in the young universe.
This energy, they theorize, would then decay faster than other radiation.
Leaving the late evolution of the universe unchanged. These observations have
also led to a controversial theory that the universe may in fact be older than the
standard model of cosmology predicts. This theory, argued by Rajendra Gupta
in a recent paper, proposes that the universe may be 27 billion years old rather
than 13.
8. This theory is based, in part, upon the concept of tired light, a theory first
proposed in 1929 by Fritz Zwicky, who suggested that if photons lost energy
over time through normal matter collisions as they travel through the universe,
that this would cause light from distant objects to appear much redder.However, this theory presents many theoretical problems of its own, and for the
time being, the standard model of cosmology remains in [00:11:00] place.
Another primary objective of the James Webb mission was to witness the
formation of the early stars and galaxies, the purpose of which was to fill gaps
in our scientific knowledge.
Astronomers have a very good idea of what galaxies look like today, based on
centuries of observation, and, thanks to the Hubble Space Telescope and its
successors, they have a good idea of what galaxies looked like roughly 13
billion years ago when they emerged from the so called cosmic dark ages. This
has allowed astronomers to chart the evolution of galaxies over time, but only to
a point.
By seeing them in their very early stages, astronomers and astrophysicists and
cosmologists hoped to test theories about galaxy formation and the role played
by supermassive black holes. To break it down, the first galaxies are theorized
to have begun formation roughly 380, 000 years after [00:12:00] the Big Bang.
This coincides with the Cosmic Dark Ages, which lasted until about 1 billion
years after the Big Bang, and which astronomers can see in visible wavelengths.
The Dark Ages, however, are so called because the universe was permeated by
neutral hydrogen. Only two sources of light, a. k. a. photons, were visible
during this cosmological period that would be accessible to astronomers today.
This includes the relic radiation of the cosmic microwave background, and
those photons that are occasionally released by neutral hydrogen atoms as they
were undergoing reionization. This reionization coincided with the formation of
the first stars in the universe, known as Population III stars. To differentiate
them from the two subsequent generations of stars, population 2 and 1, unlike
most population 2 and 1 stars, population 3 stars are theorized to have been very
massive, very [00:13:00] hot, and short lived, with main sequences that lasted
just a few tens of millions of years.
They also emitted intense amounts of ultraviolet radiation. This led to the
theoretical era of re ionization in which the clouds of neutral hydrogen were re
ionized and slowly dissipated. By one billion years after the Big Bang, the
universe became transparent, quote unquote, to modern instruments, which is to
say, observable and visible light.
Due to the tremendous cosmic distances involved, all the light that existed
before the universe became transparent is redshifted to a point that it is only
visible in parts of the infrared spectrum, which are very difficult to observe.Enter the James Webb Space Telescope, which relies on advanced optics and
infrared instruments, as well as an advanced heat shield that prevents thermal
interference.
Thanks to this combination, the earliest galaxies that [00:14:00] existed during
this period, also referred to as Cosmic Dawn, are now accessible. When
astronomers got their first look at these galaxies, they were rather surprised. For
one thing, there were far more galaxies in the early universe than the standard
model of cosmology predicted.
What's more, the galaxies themselves appeared much larger and brighter than
expected. In accordance with the Standard Model, there simply wasn't enough
time for this many galaxies to have formed or for them to accumulate as much
bright stars as they did. This too has led to some new and interesting theories
which attempt to explain this and bring Webb's observations and the Standard
Model of cosmology into agreement.
This includes a recent study by the International Cosmic Evolution Early
Release Science Survey, known by the abbreviation C E E R S. According to
the theory they advanced, the brightness that has been observed by astronomers
may be an optical illusion. In [00:15:00] theory, they argue, Supermassive black
holes at the center of early galaxies would have rapidly consumed gas, causing
friction that caused the gas to produce light and heat.
This is similar to what astronomers observe today with quasars, aka quasi stellar
objects, which refers to active galactic nuclei. Where the central region of
massive galaxies that have powerful supermassive black holes emit tremendous
amounts of radiation, causing them to temporarily outshine all the stars in their
galactic disks combined.
If this theory is correct, the light emitted by all this superheated gas would make
these galaxies appear much brighter than their population of stars would
suggest. Thus creating the illusion that these galaxies had larger stellar
populations than models predict. A similar theory has been suggested by the
JWST Advanced Deep Extragalactic Survey, or JADES.[00:16:00]
Their research suggests the universe was much denser during this early period,
which prevented early stars from pushing away clouds of gas during their
formation. This could, in theory, have led population three stars to form more
rapidly than their contemporaries, thus allowing galaxies that are larger and
more populated to have existed earlier than expected.Which brings us to another major objective of the JWST, which was to observe
the seeds of supermassive black holes during the early universe. For decades,
astronomers have known that most massive galaxies have a supermassive black
hole at their center, and this includes the Milky Way. At the Milky Way's core,
there is Sagittarius A.
This black hole has a bright accretion disk consisting of gas and dust that has
been accelerated to near the speed of light, causing the release of tremendous
amounts of energy, and has several stars in its orbit. Some of which [00:17:00]
will eventually be consumed. But, as astronomers used Webb to observe early
galaxies, they found that the seeds of supermassive black holes were also larger
than standard models predicted.
This included EGSY 8P7. A galaxy that existed just 570 million years after the
Big Bang. At the center of this young galaxy, astronomers were surprised to see
a black hole that is roughly 9 million times the mass of the sun. Even greater
than that was a supermassive black hole at the center of UHZ1, which was
observed in 2023 by Webb and the Chandra X ray Observatory.
This galaxy existed when the universe was just 470 million years old. And at its
core, a black hole of 40 million solar masses, 10 times the mass of Sagittarius
A. What's more, its host galaxy had an estimated mass of only 100 million suns,
[00:18:00] comparable to the small Magellanic Cloud, the satellite galaxy just
outside the Milky Way.
The dual observations also indicated that this black hole was not as bright as the
more massive black holes that are observed in the present day universe. A
possible theory that has been suggested is that the first supermassive black holes
may have been the result of direct collapse, which could, in theory, have given
them enough time to grow this massive.
In other words, they formed from the collapse of massive clouds of gas rather
than going through the process where gas forms stars, which eventually collapse
to form the first black holes, slowly growing over time by creating more gas and
more stars. Lastly, there are the many finds and breakthroughs that the JWST
has allowed for in the field of exoplanet studies.
As of the recording of this episode, the current exoplanet census stands at 5,
[00:19:00] 849 confirmed planets, with more than 10, 000 candidates awaiting
confirmation. There's so many exoplanets available for analysis. The trend has
began to shift from the process of discovery to characterization. In other words,
the field is transitioning from simply looking for more exoplanets towardsgetting a closer look at them so we can learn what kind of chemical abundances
they have in their atmospheres, which could indicate the existence of life.
The JWST has proven itself to be particularly excellent at exoplanet
characterization because of two key factors. For one, its large 6. 4 meter, or 21
foot, mirror collects a lot of photons that conventional telescopes cannot. This
allows the JWST to observe very dim objects, as well as objects that are very
close together.
This is very useful when conducting direct imaging studies of exoplanets, where
it is able to isolate the [00:20:00] faint light being reflected off of a planet, while
its onboard coronagraphs are able to block out the light of the parent star. The
JWST also has advanced infrared cameras and spectrographs that allow it to
break down the light of these dim and distant objects into a spectrum.
By analyzing at what wavelengths light is being absorbed and radiated outwards
in the atmospheres, it is able to produce spectra. In other words, indications of
what chemicals are present. As of the recording of this episode, the JWST has
observed 127 planets. 64 of which were gas giants comparable in size and mass
to Jupiter or Saturn while another 38 were Neptune like planets, and 31 were
rocky planets comparable to Earth.
The majority of these were observed during what is known as a transit where a
planet passes in front of its star relative to the observer. During these transits
light [00:21:00] passing through, the exoplanets atmosphere was observed by
web from which Spectra was obtained. In 15 cases, web obtained spectra
directly from exoplanet atmospheres using the direct imaging technique.
These, perhaps the most impressive was WASP 39 B, which web observed as
part of its early release science program. WASP 39 B is a Saturn size world,
less than a third of Jupiter's mass located in a system, 700 million light years
away. Webb viewed this planet with all of its instruments, which allowed the
mission team to cross validate the results, and revealed a number of interesting
things about this gas giant's atmosphere.
Among them, unexpected things like water, CO2, and sulfur dioxide. This
represented some of the very first data that came from the telescope, and
showcased the telescope's abilities to characterize exoplanet atmospheres. As
well as obtaining data about conditions beneath the upper layers, which could
include [00:22:00] atmospheric mixing, tidal heating, and chemical interactions.The funny thing is, JWST wasn't designed for this kind of research. Its
instruments and its mirrors were mainly fashioned for observing light from the
very early and distant universe. However, these same abilities have made it
particularly excellent at characterizing exoplanets. When NASA launches the
Nancy Grace Roman Space Telescope in 2027, named after the mother of
Hubble and Hubble's direct successor, the two will work in tandem.
Whereas the Rowan Space Telescope will use its advanced imaging capabilities
and wide field of view to detect tens of thousands more exoplanets, Webb will
conduct follow up observations in order to characterize them. So far, Webb has
not detected any habitable planets, but the science is nevertheless impressive,
and it does offer tantalizing clues of what's to come.
These are just some of the things that the James Webb Space [00:23:00]
Telescope will explore and discover as it conducts its five and a half year
primary mission. NASA While the observatory is planned to remain operational
for 10 years in total, decommissioning sometime in 2031, scientists expect that
it will last for at least 20 years.
And in that time, it will be joined by several next generation telescopes,
including the aforementioned Nancy Grace Roman, and also the Habitable
Worlds Observatory. This is another accomplishment that the Webb Telescope
has made since its launch in December of 2021. Which is to showcase the
abilities of next generation telescopes and their capacity for investigating the
cosmological mysteries that were introduced to us by the venerable Hubble
Space Telescope, as well as many cutting edge ground based observatories.
Astronomers are also looking forward to next generation ground based
telescopes, which fall into the 30 meter category, which is to [00:24:00] say
they have primary mirrors measuring 30 meters in diameter, or 100 feet.
However, that's a subject for another podcast. In the meantime, thank you for
listening. I'm Matt Williams, and this has been Stories from Space.