- Chris Baker
A quick Update on the JWT
Updated: Dec 22, 2021
The James Webb Space Telescope
In my original article I explained how Santa would be coming early, December 22nd in fact, as the James Webb Telescope was due for launch that day. But here we are with a few more delays. However, there is good news as it is now scheduled for Christmas Day at 12:25 pm - after your first glass of wine but maybe just prior to lunch! (If you are in the northern hemisphere!)
In any case I will send you an update on Christmas Day so if you want to watch it LIVE then I will supply a link.
This is the launch date of the long-awaited James Webb Space Telescope (JWST) – the replacement for the Hubble Space Telescope, launched 30 years ago. It has been jointly developed by NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA).
Illustration of the James Webb Telescope
This hugely ambitious project is over-budget to the tune of ten billion $’s and at least a decade late, but here we are, finally ready to fly.
What is it?
Like the Spitzer, Kepler and Hubble observatories, it is a telescope based in space. Here, the seeing conditions are optimal as the weather never changes - there is none! And there is no atmosphere to look through and disturb the faint photons arriving from afar.
On one side of the instrument there is an array of mirrors, each individually controlled, forming one large mirror 6.5 metres in diameter. This compares to the Hubble mirror of 2.4 meters. This mirror captures the light and delivers it to a range of different cameras, each designed to measure different wavelengths of light.
The light being captured is extremely faint and primarily at infra-red wavelengths – basically that of heat- therefore the mirror and instruments need to be shielded from the light and heat generated from the sun, earth, moon and the telescope itself. So there is a huge shield between the sun-facing side of the observatory and the gigantic mirror, looking deep into space.
Illustration showing the enormous sun-shield.
The sunshield separates the observatory into a warm, sun-facing side which will reach approximately 230 degrees F, and a cold side where the instruments are located, down to -394 degrees F ! The five-layer sunshield keeps sunlight from interfering with the sensitive telescope instruments. The telescope operates at around-370F.
Where will it hang-out?
The JWST will be in a completely different orbit to any other space telescopes. For example, the Hubble telescope is in an orbit around the earth at a height of about 343 miles and completes one earth orbit every 97 minutes. This ‘low altitude’ orbit has allowed for service missions, including upgrading the cameras and fixing the mirrors over its 30 year lifetime.
However, the JWST is going somewhere completely different, at a point over 1 million miles from earth and will never be serviced at this vast distance. No human has gone beyond the distance to the moon which is about 250,00 miles.
Illustration showing the position of the JWST
The telescope will not orbit the earth but follow the earth’s path around the sun at a point called L2.
There are a number of what are called ‘Lagrange Points’ - these are specific positions around the earth where the gravity from the earth, moon and sun is in balance. Therefore objects placed at these points move in a continuous stable orbit around the sun and in a fixed position relative to the earth. This is important to maintain the shield in a fixed position against the sun(light).
The instruments operate at an exceptionally low temperature and the JWST will actually orbit the L2 point, getting some shadow affect from the moon and the earth as it goes.
How does it get there?
An illustration of the deployment to L2
The journey will only take three days to be as far out as the moon and will be completed within 30 days. Extensive testing will then take place prior to the first results expected next year.
What is it going to do?
The early Universe
The JWST will be able to look back to around 200 million years after the Big Bang, when the first stars in the Universe formed.
The first stars are thought to have been massive giants made of hydrogen and helium, whose short lives ended in the supernovae that created the heavier elements we detect in younger stars today. To see this period in cosmic history, we need sensitive infrared instruments to detect the faint traces of light that have travelled through space and time to reach us.
The JWST will also look back to the very first galaxies in the Universe to learn more about their evolution and why there’s so much variety in them. Nearly all the spiral and elliptical galaxies that we see today have experienced at least one collision or merger with another local galaxy.
Yet older galaxies look entirely different to their modern counterparts – smaller, clumpier, less structured. Examining galaxies can also inform us of the macrostructure of the Universe and how it’s organised on a large scale.
Dark matter is thought to play an important role in the structure of the Universe, accounting for five times the mass of normal matter such as atoms. Considered to be the scaffolding for the Universe, we’re only able to observe dark matter indirectly by measuring how its gravity affects stars and galaxies.
The JWST won’t be able to see dark matter, but it will employ techniques to study the most distant galaxies and look at their rotation for signs that dark matter is at play.
The JWST will help answer the big question of whether life exists beyond Earth by studying a variety of exoplanets – planets outside our Solar System.
Of particular interest is the TRAPPIST-1 system, where three of its seven planets are in the habitable zone and one may harbour liquid water. The JWST will observe the planet as light from its parent star passes through the planet’s atmosphere, revealing its chemical composition and the gases that are present there.
Our ice giants
While the JWST’s primary science aims lie more in cosmology and star formation, it’ll also take a closer look at a couple of familiar objects – our ice giants, Neptune and Uranus.
The JWST will map their atmospheric temperatures and chemical composition to see how different they are – not only to each other, but also their gas giant cousins, Jupiter and Saturn. The ice giants are at least 30 times further from the Sun than Earth and are the least understood planets in our Solar System.
Pluto and the Kuiper Belt Objects
Dwarf planet Pluto and its fellow Kuiper Belt Objects will also be receiving some observation time.
The JWST is powerful enough to study such icy bodies including comets, which are often-pristine leftovers from our Solar System’s days of planet formation and could hold clues to Earth’s origins. There are no planned missions dedicated to the outer Solar System for years, so new observations and data will play a big part in planning for future planetary missions.
Why ‘James Webb’?
James Webb was head of NASA. He oversaw NASA from the beginning of the Kennedy administration through to the end of the Johnson administration, (1961-68) thus overseeing all the critical first manned launches in the Mercury through Gemini programs, until just before the first crewed Apollo flight. He also dealt with the Apollo 1 fire.
Want to see the launch Live?
I will inform everybody of the launch updates and supply the link to watch LIVE.
And finally……… Let’s hope Rudolph doesn’t over-do the brandy or carrot intake as we don’t want the rocket to go pop on the launchpad!