It is a majestic beast of astronomical proportions.
Its 6.5-metre primary mirror is a tessellation of golden hexagons resembling a honeycomb, which is mounted on a pile of silver-paper wrappers that act as sunshields, each the size of a tennis court. Now imagine all that packed into a rocket fairing five metres across, blasted off 1.5 million kilometres (1 million miles) into space and instructed to unfold, with nanometre precision, into the shape above.
The James Webb Space Telescope (JWST) is the beast in question. From ultra-smooth gold-plated beryllium mirrors to sunshields with a sun protection factor (SPF, like those in sunscreen lotions) of over a million and complex primary instruments with 250,000 individually controlled shutters.
Never before has such a sophisticated science mission been planned to be sent into space… with no crew.
Just like its predecessor – the iconic Hubble Space Telescope – the JWST scans the universe in the visible and ultraviolet (UV) spectrums. But unlike its predecessor, the JWST has sensors optimised specifically for the longer infrared wavelengths, enabling the telescope to efficiently seek three important types of objects that Hubble and ground-based telescopes can’t – the old, the cold and the dusty.
JWST digs the old.
Ever notice how the pitch of the siren on an ambulance drops as it passes by? It’s caused by the Doppler effect.
There’s a cosmic equivalent too, called “redshift”. Some objects are so old and far away that their visible and UV emissions have been stretched by the expansion of the universe into the infrared’s longer wavelengths.
Redshifts are more obvious the farther back you go, and the JWST is so sensitive that it is capable of detecting infrared emissions from almost 13.5 billion years ago. That’s only 300 million years after our Universe’s birthday! (Sounds like an eternity, but just a few seconds on the cosmic clock) That means the JWST will be powerful enough to see what happened shortly after the Big Bang.
JWST digs the cold.
Hot objects in the universe, such as quasars and white dwarves, emanate electromagnetic waves in the wavelengths of visible light.
But the cooler kids with temperatures as low as 100 degrees above absolute zero (-173.15 degrees Celsius or 100 Kelvins or -279.67 Fahrenheit), such as planets that are just forming, radiate electromagnetic waves in the infrared spectrum. This means that the JWST will be powerful enough to spot planets that are in the midst of formation.
JWST digs the dusty.
Some objects are shrouded in a cloud of mystery, literally.
Hidden in nebulae that comprise grains of matter that scatter visible light, these dusty objects can instead be seen through their infrared emissions, which are much less affected by the clouds of “dust”. This means that the JWST will be powerful enough to witness the nurseries of young stars within some of the clouds, or matter that’s being gobbled up by black holes at the centres of others.
Bonus – the dark.
To accomplish all those scientific objectives, a suite of precision instruments is required. We’ve got them covered in a previous article, click this link to learn more!
Apart from all the star-searching and exoplanet-hunting and activities that will keep the telescope busy for a while, some researchers have plans to use it to answer some of the biggest questions in modern cosmology: dark energy and dark matter.
According to cosmologists, dark energy makes up 68% of the universe’s content. It’s a mysterious, dark force that’s pulling galaxies apart, leading to the accelerating expansion of the universe.
One way the JWST may help to uncover the workings of this enigmatic substance is to measure the distances to far-off stars and stellar explosions of known brightness (or standard candles), by comparing that brightness with their perceived brightness from Earth. The expansion rate can then be estimated from the redshift of this light. With the JWST, researchers will be able to measure the distances of stars up to five times farther away than is now possible.
Dark matter, on the other hand, makes up about 27% of the cosmos. The rest – everything on Earth, everything ever observed with all instruments, all normal matter – adds up to less than 5% of the universe. (Come to think of it, it really shouldn’t be called “normal” matter at all!)
This elusive substance, believed to be crucial to galaxy formation, interacts with normal matter only through the force of gravity. Some scientists think dark matter is made of subatomic particles that have yet been discovered, such as axions or sterile neutrinos. Others think dark matter consists of primordial black holes. And a few refute the existence of dark matter with clever tweaks to Einstein’s theory of relativity. The JWST may help to distinguish between what’s right and what’s wrong.
A bright side to the long delay.
The cloud of delay surrounding the JWST, which lasted for more than a decade, has had silver linings.
Exoplanet science, for instance, was still in its very infancy when the JWST was recommended in 1996. Due to the long delay, scientific experiments associated with the field have now had ample time to mature and are now integrated into the project.
All the amazing scientific outcomes do, however, depend on the telescope successfully deploying itself. But if it all goes according to plan, for the eager researchers waiting to use the JWST it will be as if more than a decade’s worth of Christmases have all come at once.
JWST is currently scheduled to launch no earlier than 7.20 am EST on Christmas Day. You’ll be able to witness the launch on NASA’s live stream. For any updates, follow JWST’s Twitter page!
