The story of our universe begins nearly 14 billion years ago with the Big Bang.
We can still see the afterglow of this violent and sudden expansion of the cosmos.
Clumps of lurid blues and purples, known as cosmic microwave background radiation, reveal minute variations in temperature and density.
This first snapshot of what the early universe looked like 400,000 years after the Big Bang was taken in the 1990s using NASA's Cosmic Background Explorer satellite.
Fossil remnants of the Big Bang, known as cosmic background radiation, were first mapped in the 1990s. Photo: NASA
The scientists who led the work were awarded a Nobel Prize in Physics in 2006.
Nobel laureate John Mather of NASA's Goddard Space Flight Center is now leading another project that promises to tell us what happened in the next chapter of the early universe.
The James Webb Space Telescope (JWST), which is due to launch at 1.20am Sunday (NZ time) if there are no further delays, is the biggest, most powerful space telescope to ever be built.
It promises to peer back in time and space to see the very first stars and galaxies that formed from hot, dense clumps of gas and dust.
"I'm hoping that it will tell us about the beginning of everything," says Dr Mather, JWST's senior project scientist.
"If all we do is confirm the story we've already got, that would be interesting.
"But I think it's also possible there's something that we haven't guessed out there yet to be discovered."
From the beginning of the universe to now, here are five big questions astronomers are hoping the James Webb Space Telescope will help solve.
What did the first galaxies and stars look like?
The most detailed map of cosmic microwave background radiation, taken in 2013. Photo: AFP / ESA / Planck Collaboration
For the first 300,000 years or so, the universe was a hot fog of energy and seething plasma that light couldn't penetrate, known as the cosmic "dark age".
Over the next billion years as the universe expanded and cooled, the earliest stars pumped out hydrogen and helium, transforming the plasma around them.
Those first stars would have been very different to those we see today, Dr Mather says.
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"The prediction is that first stars were hundreds of times as massive as the Sun, and they would burn out in a few million years and either blow up as supernovae, or collapse into black holes, or maybe both."
But we've never been able to see how these first stars and galaxies formed.
"We are missing the very first part of the puzzle," says Amber Straughn, an astrophysicist at the Goddard Space Flight Centre and deputy project scientist on the JWST.
"One of the big questions is how we go from the dark ages, the dark part of the universe, to the universe we live in today which is filled with light," Dr Straughn says.
The earliest galaxies we've been able to see existed between 400 million to 800 million years after the Big Bang.
These galaxies were captured by the Hubble Space Telescope in a famous image called the Ultra Deep Field, which took two weeks to create.
"There are a few very rare objects in that picture that go back about that far," Dr Mather says.
This Hubble image captures galaxies as far back as 400 million years after the Big Bang. James Webb will go back even further in time.
The new James Webb Space Telescope is so powerful it should be able to peer further back in time, and create an image of the earliest galaxies in just a few hours.
"We will be able to see much closer to the Big Bang with the Webb telescope, maybe within 100 million years," Dr Mather says.
Being able to see back this far may also help us solve another mystery.
Why are there supermassive black holes at the centre of galaxies?
Lurking at the centre of every galaxy, is a supermassive black hole, millions to billions times the mass of our Sun.
The supermassive black hole at the centre of the M87 Galaxy was imaged for the first time in 2019. Photo: Event Horizon Telescope collaboration et al.
In 2019, we captured the first image of the gas swirling around the edge of a black hole six and a half billion times the mass of the Sun at the centre of the M87 Galaxy.
But we don't know how monsters like this black hole were created.
"One way that it could happen is that the first generation of stars made small black holes, and then those small black holes started to swallow up either other stars or gaseous material, or dark matter or whatever is out there to to eat," Dr Mather says.
We've started to see evidence of this process happening through our observation of gravitational waves - tiny ripples in the fabric of space-time.
But so far, we've only seen gravitational waves from relatively small objects with the mass of stars, Dr Mather says.
"So we don't know how they grow up to be millions and billions of times the mass of the Sun."
How are new stars in the Milky Way born?
These images of the Pillars of Creation in the Eagle Nebula demonstrate Hubble's ability to capture stunning images in both visible (left) and near-infrared (right) light. Photo: NASA
Stars are born in a massive cloud of gas and dust known as a nebula.
Over the years, the Hubble Space Telescope has captured stunning images of these stellar nurseries in the Milky Way.
Because nebulas are so dusty, it's hard to see what's happening under the clouds.
One the most famous images taken by the Hubble Space Telescope is the iconic Pillars of Creation in the Eagle Nebula.
On the left is what the pillars look like in the spectrum of light we can see (visible light), on the right is what they look like in a narrow range of infrared light.
The new James Webb Space Telescope will be even more powerful in the infrared range.
It should be able to see even deeper into the dark splotches in the image on the right.
The images will be stunning, Dr Straughn says.
"One of the great things about infrared light is that it allows us to peer down into those dust clouds where stars and baby planets are forming."
Is there another planet out there like Earth?
Seven Earth-sized planets have been discovered orbiting a nearby star known as TRAPPIST-1. At least three may be in the habitable zone. Photo: NASA/JPL-Caltech
A little over a decade ago, we only knew of the planets in our own Solar System.
But with the advent of planet-hunting telescopes that survey the sky, such as the Kepler Space Telescope and its replacement the Transiting Exoplanet Survey Satellite (TESS), we've now discovered more than 4,800 planets orbiting alien stars.
"There are almost certainly more planets in the Milky Way than there are stars," Dr Straughn says.
Some of these planets are unlike anything in our Solar System, such as planets known as sub-Neptunes, which are larger than Earth but smaller than Neptune.
Other planets are similar in size to Earth and orbit their sun's habitable zone - the point at which temperatures might be suitable for hosting life.
For example, the TRAPPIST solar system located about 40 light years away has seven planets orbiting a red dwarf star about 9 per cent the mass of our Sun.
In theory, three of the four planets may have temperatures that are suitable for water to form if the planets have an atmosphere.
"We don't even know if [Earth-like planets] have atmospheres," Dr Mather says.
Stars like TRAPPIST-1 tend to have violent outbursts that could make the planets inhospitable.
Astronomers identify whether planets have atmospheres by looking at the chemical signature of light passing through gas as the planet passes in front of its star.
This technique, known as spectroscopy, identifies different molecules of such as water, carbon dioxide and methane, which absorb light at particular wavelengths.
"But if a star is very small, then a planet the size of Earth actually absorbs a lot of its light," Dr Mather says.
"At the moment, we can't do spectroscopy on our little Earth-like planets at all."
This is about to change with the James Webb Space Telescope.
Using its sensitive infrared spectrometers, astronomers are planning to do the first detailed study of the atmosphere of a habitable-zone planet.
The extra spectrometer power will also come in handy for sniffing out signs of potential life - and supporting space missions - much closer to home.
Could alien life exist in our own Solar System?
Jupiter's moon Europa may have an ocean under its ice. Photo: NASA/JPL-Caltech/SETI Institute
Jupiter's moon Europa was discovered by Galileo in 1610.
Surveys of Europa by the NASA Galileo spacecraft in the 1990s suggested there was an ocean beneath its cracked, icy surface.
"And we discovered fairly recently that there are little jets of water that come out between the cracks in the ice," Dr Mather says.
This opens the question about whether or not this icy satellite of Jupiter may have conditions that could support life.
NASA is planning to send a new spacecraft to Europa within the decade to survey its surface and atmosphere to find out.
"We're also going to watch [Europa] with the Webb telescope," Dr Mather says.
The JWST will also be used to look at Titan, one of Saturn's moons.
"The surface of Titan is cold enough that ethane and methane, which we use as fuel here on Earth, are liquid," Dr Mather says.
"The surface has liquid rain, lakes, maybe even rivers, so there is interesting weather and geology on Titan."
NASA is also planning to send a mission to Titan in 2034.
The Dragonfly rotocopter will fly multiple sorties to take samples and examine sites around Saturn's icy moon.
"We will need the Webb to last a long time, to really confirm [those conditions on Titan], but we'll be watching it from as soon as we can."
