Audio Listen: https://on.soundcloud.com/zHZYG
Transcript:
“Welcome to the Astrophiz podcasts….
My name is Brendan O’Brien, and we’d like to acknowledge Australia’s first astronomers, the Aboriginal and Torres Strait Islander people, the traditional owners and custodians of the land we are on.
This episode is produced on Yorta Yorta country.
Before we start, we’re asking you to influence your local politicians with the message that we really need to change our energy policies and move to renewable energy sources to mitigate the effects of climate change.
And each month we love bringing you two fabulous episodes … on the first of each month. Our friend, molecular Pharmacologist Toxicologist, and Amateur Astronomer Dr Ian ‘AstroBlog’ Musgrave brings us his monthly sky guide with all the essential observational highlights for telescopers, astrophotographers, and naked eye observers
Ian also includes ‘Ian’s Tangent’, where he takes us on a short journey of astronomical wonder …
… and in the middle of each month we bring you an exclusive and in-depth interview with a noted astrophysicist, astronomer, particle, physicist, radio telescope engineer, data scientist, or space scientist.
In next month’s November episode we have Dr Rebecca Davies from ASTRO3D who uses spectroscopic data from Hubble, JWST, the awesome James Webb Space Telescope and the VLT, the Very Large Telescope to bring us new understandings of how galaxies evolve.
And for December’s episode we’re looking forward to zooming over to Cambridge Massachusetts to the Harvard Smithsonian Centre for Astrophysics and we’re speaking with PhD candidate Hyerlin Cho who is fingerprinting black holes and FRBs
But today’s special episode features a truly fabulous guest.
Yes, finally we have Brendan O’Brien on the show in the speakers chair.
But don’t worry, I won’t be interviewing myself …
Today’s episode is all about the amazing James Webb Space Telescope
“Unveiling the Cosmos”
This is for our regular listeners, new listeners, space enthusiasts, and those with a curious heart
Our story begins in a remote, microscopic corner in the vast expanse of the cosmos, where humankind has always yearned to uncover its deepest mysteries.
The James Webb Space Telescope (JWST) represents a monumental leap in our quest to explore the universe.
From its conception as an ambitious dream … to its launch on Christmas Day 2021, … it’s successful deployment and calibration has resulted in the mindboggling imagery that it is constantly beaming back down to us; the JWST has already been a testament to human ingenuity, perseverance, and the unquenchable pursuit of new knowledge.
The JWST story begins in the late 1980s when astronomers and scientists first envisioned a telescope capable of peering into the distant realms of the universe with unprecedented clarity. This idea was born out of the desire to succeed the Hubble Space Telescope (HST), which had already provided us with breathtaking images of the cosmos.
The Hubble’s success demonstrated the enormous potential of space-based observatories, but it also revealed some limitations due to Hubble’s location in LEO, low Earth orbit.
Hubble was … and is … an unmitigated success, and after 33 years on mission, it is still bringing to both the public and to scientists … images of unprecedented clarity of both well-recognised and new astronomical targets.
Many listeners will still remember when they first saw the now iconic Hubble images of the famous Horsehead nebula in Orion’s Belt, and more recently, the latest Hubble images of the Extreme Deep Field are truly mind-shaking.
If you haven’t seen the Extreme Deep Field, the XDF, just pause your audio player if that’s convenient, and put ‘Hubble XDF’ into your search engine and have a look right now.
Imagine holding a grain of sand at arms length up against the night sky where there are no stars near your grain of sand. That is what Hubble was looking at.
What you have just seen is a Hubble XDF image made from 2 million seconds or 23 days in total from Hubble’s two prime cameras looking just at one tiny pitch-dark patch of sky in the southern hemisphere … and each of those glowing points and swirls in that image is not a star, but a galaxy.
This famous Hubble image contains approximately 5,000 galaxies, extending back in time to within a few hundred million years of the big bang.
So Low earth orbit was a very prescient choice for Hubble, because it meant that it could be serviced by NASA’s Space Shuttle program.
There have been 5 service missions, the first one corrected a problem with Hubble’s primary mirror in 1993, which could have been disastrous if Hubble was parked in a high earth orbit ….. subsequent service missions added solid state recorders, new batteries, new gyroscopes, cooling systems, enhanced infrared cameras and spectrographs.
It has released some of the greatest images humanity has ever seen. If you haven’t been gobsmacked by Hubble’s now iconic “Pillars of Creation” in the Eagle Nebula, then you haven’t been gobsmacked
For those who want to compare Hubble’s view of the ‘Pillars’ and the James Web Space Telescope view, simply go to tinyurl-DOT-COM/jwsthubble (all lower case, all one word)
So Hubble is legendary, but it has reached its absolute limit for new science. It is limited by it’s small size, aging instrumentation, warm temperatures, limited wavelength range and the most limiting factor is its low earth orbit, where it even picks up the Zodiacal Light, the interplanetary dust that permeates our solar system and is brightly illuminated by the sun.
So the dream of a space telescope far beyond Earth’s atmosphere, in a location that would allow it to observe the universe unimpeded in ways never before possible, began to take shape over 30 years ago.
This concept for a next-generation space telescope gained traction in the 1990s, not long after the Hubble launch, leading to the formation of committees, working groups, and international partnerships. The project soon became a collaborative effort between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA).
What truly sets the JWST apart is this extraordinary international collaboration that brought all its critical instruments to life. Scientists and engineers from all around the world joined forces to build and test these scientific marvels. Each instrument represents the pinnacle of human ingenuity in its respective field.
The planning stage was a exhaustive process over decades … involving astronomers, engineers, and scientists from all around the world.
They had to consider every aspect, starting with the science goals, then to the telescope’s scientific instruments and their capabilities … to its destination in space.
Science research goals
Four main science goals were established early in the process.
Those goals were centred on four big questions, four big gaps in our knowledge.
From the very start, the designers knew that Webb would be a powerful time machine with infrared vision that could peer back over 13.5 billion years to see the very first stars and galaxies forming out of the darkness of the early universe.
1. So the first mystery is exactly what the universe’s first light looked like just after the Big Bang, because exactly when these first stars formed is not known.
2. Secondly, we don’t yet understand how galaxies assemble over billions of years, we don’t know how matter is distributed and behaves at multiple size scales in our quest for this understanding.
From peering into the way matter is constructed at the subatomic particle level to the immense structures of galaxies, dark matter and the cosmic web that spans the cosmos, each scale gives us important clues as to how the universe is built and evolves.
So JWST had to have unprecedented infrared sensitivity with the capacity to help astronomers to compare the faintest, earliest galaxies to today’s grand spirals and ellipticals.
3. Webb had to be able to see right through and into massive clouds of dust that are opaque to visible-light observatories like Hubble, where stars and planetary systems are being born.
4. Astronomers have already identified over 5500 exoplanets using space telescopes like Kepler and TESS. Webb had to tell us more about the atmospheres of extrasolar planets, and perhaps will even identify the building blocks of life elsewhere in the universe. In addition to other planetary systems, Webb is also studying objects within our own Solar System.
So …. In summary the JWST design had to allow us to study the formation of the very earliest galaxies, observe the birth of stars and planets, and has already proven that it can analyze the atmospheres of distant exoplanets. It had to open new vistas of exploration and provide answers to questions we have hardly dared to ask, and provide a platform from which we could look forward to asking questions we have previously not even known to ask.
The big-ticket items in the JWST Overall Design are the mirror & sun shield
One of the most remarkable aspects of the JWST is its technological prowess. Engineers and scientists had to overcome numerous challenges to create a telescope mirror & sun shield that could survive and function in the harsh environment of space.
The telescope’s primary mirror, a staggering 6.5 meters in diameter, had to be constructed in segments and folded for launch by an Ariane rocket that was only 5.4m in diameter. JWSTs multilayered sunshield is the size of a tennis court, and is designed to protect the delicate instruments from the intense heat and radiation of the Sun.
And the instruments themselves, each a marvel of precision engineering, were built to capture and analyze the faintest light from the oldest and most distant celestial objects.
Unlike Hubble, which did a lot of its work in the visible spectrum, the JWST’s primary mission is to observe the universe in the infrared spectrum, allowing us to peer through cosmic dust clouds, unveil the birth of stars and galaxies, and even study the atmospheres of distant exoplanets. To achieve this monumental task, we needed mirrors and instruments of unparalleled precision.
With the memory of Hubble’s initial problems with its mirror still in the minds of JWSTs engineers and designers, the testing the JWST’s mirrors was a meticulous and herculean task.
In the vacuum of space, the temperature can drop to -223 degrees Celsius (or -370 degrees Fahrenheit).
Therefore, the mirrors needed to withstand extreme temperature fluctuations while maintaining their shape and alignment. Engineers subjected the mirrors to rigorous cryogenic testing, pushing the limits of what was technologically possible.
The heart of the JWST is its remarkable primary mirror, a colossal 6.5-meter diameter masterpiece composed of 18 hexagonal segments made of ultra-lightweight beryllium. These segments were perfectly shaped and polished to nanometre-level precision, enabling the telescope to capture the faintest of infrared light from distant galaxies. The mirror segments’ unique hex design was a necessary design priority which allowed them to be folded for launch aboard the Ariane 5 rocket.
Lagrange points
What emerged from the science goals was a vision for a space telescope that would be positioned where it could face away from the sun and be far away from the earth and its attendant complications like space debris and zodiacal light.
There was only one stable place far enough away yet within sailing distance from earth.
That place is known as earth’s second Lagrange point.
It was decided that the JWST would be stationed at the second Lagrange point (L2), some 1.5 million kilometers from Earth, providing a stable and unobstructed view of the universe, in an orbit positioned so the earth is always between the Sun and the JWST. With the sun always at its back, the JWST was going to look into the deepest realms of the universe.
Lagrange points are pretty awesome places in space near planets where the gravity from the sun and the planet are balanced out … each planet has five LaGrange points, and an object like a spacecraft that is placed there will just stay there and not wander about.
Two hundred years ago, a French mathematician worked out there had to be five Lagrange points in any two body system … for those who have forgotten his name …. Probably Lagrange.
Some Lagrange points are more stable than others and the L2 Lagrange point is a million miles from earth on the side opposite the sun and is particularly stable so we’ve parked a few telescopes and probes there in the past, but for once we’ve been smart and once those spacecraft had fulfilled their missions we’ve sent them crashing into the sun or sailing off on a safe heliocentric orbit, so that now the JWST is one of only a few telescopes parked at L2, so it can safely make observation runs without the danger of crashing into another spacecraft or until some billionaire wants to build a robotic Tesla factory or fulfillment centre there.
Currently, the JWST shares L2 with ESA’s Gaia probe and Euclid telescope and the Joint Russian-German high-energy astrophysics observatory Spektr-RG, but to be fair, the L2 Lagrange Point is not really a ‘Point’. Rather it’s a relatively large region of space which is gravitationally ‘balanced’ … and to be fair, there is enough room at L2 for thousands of spacecraft.
Space is a very whimsical and lawless place where existing treaties and international laws are tissue thin.
I have been in touch with a space lawyer and we will do an episode on the murkiness of space law next year.
But I diverge …
Back to the next chapter in our JWST story …
Construction & Testing
As construction of the JWST progressed, rigorous testing became a crucial part of the development process. Engineers and scientists needed to ensure that the telescope could withstand the jolting rigors of launch and space travel and operate flawlessly once deployed.
Thermal testing, vibration testing, and a battery of other assessments pushed the limits of technology. The JWST had to survive both the extreme cold of deep space and the intense radiation of the Sun.
It had to withstand the forces of launch and the vacuum of space. Each test brought the telescope one step closer to its ultimate goal.
Every component was subjected to the test bed … all eventually passed with perfection.
Lets look at the instruments on the JWST
So the JWST is much more than just its signature mirrors; it’s equipped with four state-of-the-art scientific instruments, each designed to probe different aspects of the universe.
The instruments are : The Near Infrared Spectrograph (NIRSpec), the Mid-Infrared Instrument (MIRI), the Near InfraRed Camera (NIRCam), and the Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph .;… that’s quite a mouthful so the locals just call it the FGS-NIRISS.
All were designed and tested to all work together seamlessly to fulfil the science goals and unlock the universe’s mysteries.
The journey to design and test the mirrors and instruments on the JWST was not without its challenges.
Originally slated for launch in the early 2000s, the telescope’s launch date was repeatedly pushed back due to technical challenges, budgetary constraints, budget overruns, embarrassing delays and unforeseen obstacles.
There were Twitter memes and jokes about the receding JWST launch dates.
but the unwavering dedication of the project managers, scientists, engineers, and countless others involved … kept the dream alive for a further twenty years … the work continued … Their resilience in the face of adversity is a testament to human determination and the pursuit of knowledge.
When testing, construction and assembly and more testing were completed, a Launch could be finally scheduled.
So …., thirty odd years after the concept started, the launch was ready, and as we stood on the precipice of the JWST’s launch, on the 25th of December 2021, all around the world space enthusiasts, amateurs and professionals, many whose entire careers were immersed in this gargantuan project, all were filled with intense anticipation and excitement. The years of design and testing had led us to a moment when the JWST would embark on its long journey to the second Lagrange point, 1.6 million kilometers from Earth.
The lucky ones were at the Launch site in Kourou in French Guiana, just above the equator in South America. The rest of us gathered online to witness this historic event, and were reminded of the human capacity to dream big and to have the determination to make those dreams a reality.
As the countdown began, I saw that the JWST was not just any space telescope; it is a technological marvel, an absolute masterpiece of engineering.
Mounted atop an Ariane 5 rocket, it was poised to leave Earth’s atmosphere and make its way into the cosmos.
The launch was an unique experience, not just because of its destination 1.6 million kilometers away, but also because of the immense challenges involved in sending such a delicate and intricate instrument like the JWST into the unforgiving environment of space.
One tiny, microscopic mistake in construction and assembly, or one minuscule error in a line of code would put billions of dollars down the toilet of history.
For so many people who had spent their whole careers on this project, this was very scary …. Very scary.
So the next stage was the flight & deployment
And after the countdown, in French of course … the Ariane 5 rocket roared to life, the world held its breath.
<inserted: 30 second countdown and liftoff audio, via NASA archive>
Lift-off was perfect.
The JWST’s journey to L2 was a complex and carefully choreographed dance … a cosmic ballet.
After launch, on December 25, 2022, components unfurled in predetermined sequence, solar arrays deployed, antennas parked and pointed back to earth, mid course correction burns, then three days into the voyage, the sunshield begins to be deployed, by day ten the sunshield is fully deployed, tested and operational. Then over the next seventeen days the segments of the primary mirror are unfolded into its operational configuration.
After an insertion burn, Webb arrives at L2 on January 24.2022: and
Parking orbit at L2 was done with perfect precision. Another flawless milestone.
At this unique vantage point, the JWST has an unobstructed view of the universe, shielded from the blinding glare of the Sun, and looking out and away from the sun and free from the disruptive effects of our planet’s atmosphere and interplanetary dust.
For the next three and a half months, the mirror components were then perfectly aligned to the instrument fields of view and the whole assembly cools right down to operational temperature and the coldest instrument MIRI … reached its final operating temperature below 7 kelvin , which is minus 266 degrees Celsius or minus 447 degrees Fahrenheit.
Images
Webb began ‘first light’ observations on July 12 2022.
The first clear image captured by the JWST is magnificent and as the telescope’s sensors began to collect data, a breathtaking image of the cosmos began to take shape with each bright star in the field having JWST’s signature: being the six-pointed spikes of light produced by the three mirror struts.
One of JWST’s first already iconic science images shows the “Cosmic Cliffs.” revealing emerging stellar nurseries and individual stars in Carina Nebula that were previously obscured by dust.
Once again, you may wish to pause and have a look at JWSTs ‘Cosmic Cliffs’ image. I can recommend putting JWST ‘Cosmic Cliffs’ into you search engine and have a look at this beautiful image, what you will see is a seemingly three-dimensional picture of what looks like craggy mountains on a moonlit evening.
It is magnificent!
What you see here is a collection of dust and gas which is part of the huge Carina nebula, only visible in Southern skies. Another great reason to visit the southern hemisphere.
We do have the best skies … and drop bears.
Sorry, not sorry, … but back again to JWSTs ‘Cosmic Cliffs’ …. Here, some 7,600 light-years from Earth, many massive stars were being born. The Hubble Space Telescope created magnificent images of this nebula in visible light, but JWST now shows the nebula’s “infrared fireworks,” and the nebula appears especially spangled with brand-new stars that were previously completely hidden from our view,”
You are looking at the very edge of the giant, gaseous cavity within the Carina Nebula, NGC 3324, and the tallest “peaks” in this image are about 7 light years high. The cavernous area has been carved from the nebula by the intense ultraviolet radiation and stellar winds from extremely massive, hot, young stars located in the centre of the bubble, just above the area shown in this image.
The vicious ultraviolet radiation from the young stars above is sculpting the nebula’s wall by slowly eroding it away. Dramatic pillars tower above the glowing wall of gas, resisting this radiation. The “steam” that appears to rise from the celestial “mountains” is actually hot, ionized gas and hot dust streaming away from the nebula due to the constant radiation pressure.
It is now Webb is 22 months into its mission …. Performing flawlessly and producing amazing science that is re-writing our understanding of the early appearance of stars and galaxies in the universe.
Researchers are now learning more about these early galaxies’ masses, ages, histories, and compositions, and Webb is now hunting down even earlier galaxies in the universe.
Webb has also captured the distinct signature of water, along with evidence for clouds and haze, in the atmosphere surrounding a hot, puffy gas giant planet Exoplanet: WASP-96 B which is orbiting a distant Sun-like star.
demonstrating Webb’s unprecedented ability to analyse atmospheres hundreds of light-years away
Webb has captured a Dying Star’s Final ‘Performance’ in fine detail, filling in large gaps in our knowledge of stellar evolution.
Thanks to Webb’s huge image of Stephan’s Quintet, a group of 5 close knit yet disparate galaxies interacting in a delicate and complex cosmic dance we now have new insights into how galactic interactions may have driven galaxy evolution in the early universe.
The universe is laid bare under Webb’s unwavering gaze.
So finally
The JWST represents more than just a telescope; it is a symbol of human potential, collaboration, and the unquenchable thirst for knowledge. It is a beacon of hope for all those who dream of exploring the cosmos and a reminder that, even in the face of adversity, we can achieve the seemingly impossible.
In the coming years, the James Webb Space Telescope will revolutionize our understanding of the universe. It will provide us with more breathtaking images, unveil cosmic mysteries, and inspire generations to come. The mirrors and instruments on the JWST are not just tools; they are windows to the cosmos, allowing us to gaze into the depths of space and time.
Webb reminds us that when we reach for the stars, when we dare to dream, and when we work together, when nations work together, there are no limits to what we can achieve.
Congratulations NASA, and its partners the European Space Agency and the Canadian Space Agency.
Thank you for joining us on this remarkable journey, and may the JWST’s mission illuminate the cosmos and the human spirit for generations to come.
Standing on the shoulders of giants is what we do.
We’ll see you in two weeks for Dr Ian Musgrave’s November SkyGuide
Keep looking up!”
Radio Waves …
The Astrophiz Podcast 