The James Webb Telescope - Launching a time machine to space
If you had a time machine …when and where would you go?
Would you travel to the future to be first in line for the next iPhone 800?
Or, would you travel to the past to see a T-Rex?
Or, maybe you would just like to speak with a loved one once again?
Whatever the time and place that you choose…
What would you do then?…How do you think you would feel?…and how would that experience change the rest of your life? Those seemingly simple questions have answers that would shape your future in complex ways.
Today, scientists have the rare opportunity to “travel” back in time and ask fundamental questions that will shed light into the origin of our universe. Sounds too good to be true right?! Let’s dive into this to see how this is all possible.
First things first: Telescopes are actually time machines…but how?!
When you look up at the night sky and see the lights coming from flickering stars, you are actually seeing light from many years ago. You see the stars as they once were, not as they are in the present moment! It’s hard to believe but stay with me here.
Picture a flashlight that you turn on and off to emit a quick pulse. The light traveling from that flashlight is so fast, that it could go around planet earth 7.5 times in a single second! Light is the fastest thing in our universe (186,000 miles per second) and it is commonly known as the universal speed limit. That means that nothing else in existence can travel faster than light. Although the speed of light may seem impressive, it’s still no match for the vast distances of space.
The size of our universe is mind-boggling. Here’s an example: Proxima Centauri, the closest star to our sun is more than 24,690,226,567,371 miles away. To help simplify these large numbers, scientists have invented a unit of measurement called, the light year. One light-year is equal to more than 6 trillion miles or the distance covered by light in a single year. Proxima Centauri’s distance of +24.6 trillion miles can also be described as 4.2 light-years away. Phew, much easier to say it that way!
Imagine that…the fastest thing in our universe is still painfully slow in the context of cosmic distances.
Looking back in time
In the year 1610, Galileo Galilei, the father of observational astronomy, used a simple refracting telescope to be the first person to observe Mars. Light from Mars travels 234 million miles in 3 minutes to reach Earth. In a very real way, Galileo was observing Mars as it had been 3 minutes in the past.
Galileo saw light from Mars 3 minutes in the past
Fast forward 400 years after Galileo’s first observations, and our telescopes have gotten much more advanced. Today, our telescopes are able to observe light from billions of years in the past. These observations have been instrumental to our understanding of the cosmos…but there is still much more to learn!
The ESO Observatory in Chile sees light billions of years old
The making of the James Web Space Telescope
The development of this time machine began back in 1996 with a $500 million budget. Unfortunately, the project has been riddled with delays, technical issues, and a whopping bill of $10 billion.
The 25 years of development amount to the collaboration of more than 306 organizations from +14 countries, the combined effort of thousands of scientists, engineers, and technicians who invested over 40 million labor hours in this monumental project.
The James Webb Space Telescope is a feat of human ingenuity that will help answer fundamental astronomy questions and will provide a new view of the universe that has never been seen before.
It’s a giant leap forward in our quest to understand humanity’s place in the great cosmic expanse.
Space United with the JWST in California (Nov 2019)
How far back will the James Webb Space Telescope see?
For reference, The Hubble Space Telescope has observed the birth of modern galaxies, with less definition and more compact structures. The Hubble images gave us a glimpse of galaxies that look very different from the pictures of the galaxies that are closer to us in space and time.
With the James Webb Space Telescope, astronomers will be looking back even further than the Hubble telescope; into a time where the universe’s very first galaxies were just forming!
At this early stage in the timeline of our universe, gravity had already condensed gas into the first stars. These stars produced the first heavy elements necessary for life, like carbon and oxygen.
A few million years later, the second generation of stars formed from this enriched gas. Gravity began grouping these stars into young galaxies. The James Webb Telescope will capture images that show the structure and composition of these first galaxies, teaching us about the formation and lifecycles of the galaxies in our universe.
How does this cosmic time machine work?
The James Webb telescope is absolutely packed with unprecedented scientific power. The telescope is so sensitive that it could even detect the heat signature from a bumblebee 240,000 miles away!
The telescope has 4 main instruments:
1. The Near-Infrared Camera (NIRCam) is the telescope’s primary imager in the near-infrared range that can capture wavelengths in the range of 0.6 to 5 microns. In other words, this allows the telescope to use ten sensitive detectors to get high-resolution images and use spectroscopy for a wide variety of investigations. (More on what spectroscopy is on a future blog!)
2. The Near-Infrared Spectrograph (NIRSpec) is a versatile instrument designed to observe 100 objects simultaneously. This will be the first instrument in space with multi-object capability. It includes 248,000 tiny cells as wide as a single hair called the “micro shutter array”. These shutters open and close when a magnetic field is applied. Each cell is controlled individually, which allows the telescope to focus on multiple objects while ignoring irrelevant light!
3. The Fine Guidance Sensor (FGS) provides near-infrared imaging and spectroscopic capabilities. The FGS is a camera system designed to make sure Webb is stable and pointing in exactly the right direction throughout the observation. The FGS detects and identifies guide stars and ensures that Webb is locked onto those stars for the entire observation.
4. The Mid-Infrared Instrument (MIRI) will allow the telescope to see farther than any of the other infrared instruments onboard. Working on the infrared spectrum means that the telescope will be able to see through space dust and capture never before seen images! This tool is by far the most technically advanced aboard the telescope and for it to work properly it has to be kept at extremely cold temperatures. The instrument is so sensitive to heat that the telescope’s own operating heat could ruin the images with “noise”. To solve this issue the James Webb is equipped with a two-stage cryocooler that works like the world’s most effective refrigerator. It pumps a warmth absorbing gas (Helium) through the instrument. The first stage brings MIRI’s temperature down to 18 kelvin, and the second stage brings the MIRI detectors to below 7 kelvin — that’s just 7 degrees above absolute zero, the theoretical temperature at which all motion freezes!
Keeping the telescope’s instruments cold
The James Webb Space Telescope will observe primarily the infrared light from faint and very distant objects. To be able to detect those faint heat signals, the telescope itself must be kept extremely cold. To protect the telescope from external sources of light and heat (as well as from heat emitted by the operating instruments), the telescope has a 5-layer, tennis court-sized sun shield that acts like a parasol providing shade.
In addition to the shades, the James Webb Space Telescope will be 1 million miles away from Earth and set to orbit around the sun (by comparison, the Hubble Space Telescope orbits the Earth and is only 340 miles away from Earth!)
The large sun shield will protect the telescope from the light and heat radiated from the Sun, planet Earth, and even our Moon. The temperature difference between the hot and cold sides of the telescope is huge - you could almost boil water on the hot side while freezing nitrogen on the cold side!
Launching a time machine
The James Webb Telescope is 22 feet in diameter, making it over 2.5x larger than Hubble’s primary mirror. It has 18 hexagonal mirror segments that are made from a lightweight metal called beryllium. Each segment is coated with a microscopically thin layer of gold 700 atoms thick. Although the James Webb will be much larger than Hubble’s mirror, the James Webb’s specialized materials will make it weigh only half as much as the Hubble!
Currently, we don’t have any rockets that can carry something as large as a tennis court to space. For that reason, the James Webb telescope was designed to be folded up to fit into the narrow fairing of the Ariane 5 rocket made by the European Space Agency.
The Ariane 5 rocket was picked as the launch vehicle because it is a very reliable rocket (with a success rate of 95.5%); it uses a combination of stages powered by solid and cryogenic liquid propellants that will give the telescope a powered flight time of approximately 27 minutes.
Following the launch, the telescope will start a complex deployment sequence that takes nearly a month to complete. This space choreography was tested and practiced many times here on Earth because if any of these steps fail, it will render the telescope completely useless!
The Webb telescope will have an action-packed six-month commissioning period, during which it will fully deploy, cool down to operating temperatures, align its mirrors, and calibrate its instruments. On December 22, 2021, we begin a journey of discovery that will take us to the beginning stages of our universe. We will have the answers to many questions that will shape the future of humanity (Questions like: Are we alone?). It is incredible to think that by this time next year we may have to rewrite many of our science textbooks given what is yet to be discovered!
About the author: Sebastian Tobacia
Manufacturing engineer with nearly a decade of experience in the space exploration industry. Sebastian has led engineering projects at SpaceX, Northrop Grumman, and currently works on the New Shepard rocket at Blue Origin.
Sebastian is passionate about giving back to his community and working towards a more equitable and inclusive STEM industry.
