The adolescent phase of the universe was much more complex than imagined, detailed snapshots of the early cosmos from the James Webb Space Telescope (JWST) reveal.
"There are many more galaxies with obvious disks, bulges, spiral arms … appearing earlier in cosmic time than we thought," Karl Glazebrook says.
Professor Glazebrook and his colleague Colin Jacobs, from the James Webb Australian Data Centre at Swinburne University, are part of an international team known as GLASS, which is looking back at some of the earliest galaxies.
Most galaxies in the universe formed between 2 and 5 billion years after the Big Bang, but they appeared as unstructured blobs in Hubble images.
Now, data from the JWST, which has been translated into the colour range that the human eye can see, reveals a jewel box of galaxies as they appeared between 8 and 11 billion years ago.
"We can see fainter galaxies than ever before, we can see more detail than ever before, and now we can see what the human eye would see at these very ancient times," Dr Jacobs says.
The new portrait of the adolescent cosmos is just one of the surprises emerging, as scientists from different teams all over the world scramble to analyse data collected by the JWST in its first month of full operation.
"People are pouncing on it at once because it's a once-in-a-lifetime snapshot of part of the universe we couldn't see before," Dr Jacobs says.
"It's hard to overstate the excitement and the feeding frenzy."
Not only has the first data produced spectacular images of galaxies near and far, the race is on to detect the earliest galaxy.
The earliest galaxy in JWST's first deep field SMACS 0723 image released last month was estimated to have appeared about 700 million years after the Big Bang.
Since then, several different teams have detected a number of potential even earlier contenders that (if proven true), smash expectations of what even JWST could achieve, and challenge theories of the early universe.
So let's explore some of the other galaxies emerging from the dust and depths of our cosmos over the past month.
Beautiful bar galaxy NGC 7496
This spectacular image of NGC 7496 combines views taken by the James Webb Space Telescope and the Hubble Space Telescope.
Supplied: NASA, ESA, CSA, STScI and Judy Schmidt
The mid-infrared JWST image of NGC 7496 shows an active supermassive black hole at the centre of the galaxy.
Supplied: NASA, ESA, CSA, STScI and Judy Schmidt
NGC 7496, which lies just 24 million light-years away in the constellation of Grus, is a bar galaxy, explains Robin Cook, who studies galaxy evolution at the University of Western Australia.
"It's got not only these spiral arms, but it has this very distinct bar running through it," Dr Cook says.
"This is quite a common structure in galaxies — we think our own Milky Way has a bar."
The infrared image (above) reveals the skeletal structure of the galaxy, which is hidden in the Hubble image in the comparison tweet below from the team studying the galaxy.
"You can clearly see how gases funnel through the galaxy along these spiral arms and along this bar structure, which you don't see in optical light," Dr Cook says.
Grand swirling spiral M74
M74, located 31 million light-years away in the constellation of Pisces, is a stunning "grand design" spiral galaxy.
The JWST image reveals broiling spiral arms that are pockmarked with cavities.
Supplied: NASA, ESA, CSA, STScI and Judy Schmidt
Hubble's view of the galaxy is shrouded by dust.
NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: R. Chandar (University of Toledo) and J. Miller (University of Michigan)
"What's happened here is that a star has been born within the spiral arms and then it's gone supernova," Dr Cook says.
The shockwave from the exploding star has carved a cavity of space around it in a similar way to the Southern Ring Nebula seen in the first JWST images.
"But you're seeing individual ones of those within an entire galaxy," Dr Cook says.
Cosmic car crash
Cosmic collisions in nearby galaxies provide a window into the evolution of the early universe, says Lee Armus of the California Institute of Technology.
Dr Armus's team is studying four galaxies in our local neighbourhood, including IC 1623, located a mere 275 million light-years away in the constellation of Cetus.
The image below strips away the dust and emphasises the rich star-forming areas.
In the JWST data, the galaxy on the left of this beautiful duo is the most prominent.
Supplied: NASA/ESA/CSA/STScI/R. Colombari
In the Hubble image, the less dusty scorpion-shaped galaxy on the right is the brightest.
Supplied: ESA/Hubble/NASA, R. Chandar
"These are just the brightest of a tonne of hidden star formations that we couldn't see before," Dr Armus says.
Dr Armus says the "yin and yang" difference between the two views highlights the importance of studying colliding galaxies in different wavelengths.
A different view of the galaxies (below), processed by his own team to match mid-infrared wavelengths, reveals ghostly filaments.
"Those are small little dust grains that are being lit up by the radiation that's coming from this burst of activity that's happening," he says.
"It's like this huge diffuse filamentary glow of dust that just goes over a much larger area than I had expected."
About 90 per cent of all the energy in the pair is coming from the heart of the galaxy on the left.
The team is not sure whether this is coming from a powerful burst of star formation, or an elusive supermassive black hole hidden deeper in the dust.
When galaxies collide, they activate supermassive black holes, which blast out jets of radiation as they feed on gas and stars that venture too close, but the team can't find one in the data they've analysed so far.
"We're having a hard time finding real evidence for [the supermassive black hole], and it could actually be much more buried than we had suspected," Dr Armus says.
But, he stresses, the team still have to complete their analyses before they come to any conclusions.
A rare cartwheel
The spectacular Cartwheel Galaxy is one of the few images officially released by the JWST team so far.
The rare ring-shaped galaxy, which lies 500 million light-years away in the constellation of Sculptor, has been shaped by a collision with another galaxy that has long since fled the scene.
As the other galaxy punctured through the heart of the Cartwheel, it produced an effect akin to dropping a stone in a pond, first pushing material out to the edges, then funnelling material back into the central area.
This JWST image, which combines near-infrared with mid-infrared, shows there are many stars (blue spots) amidst the red swirls of dust.
Supplied: NASA, ESA, CSA, STScI
JWST's near-infrared image shows lots of young stars (yellow, pink and blue) in the galaxy's outer ring. The small galaxy to the top left appears to be made of the same material.
Supplied: NASA, ESA, CSA, STScI
JWST's mid-infrared image shows lots of young stars heating up dust in the bottom right of the outer ring, causing it to glow orange.
Supplied: NASA, ESA, CSA, STScI
The new images reveal much more information about the star-forming areas around the edge, as well as the central ring, Dr Cook says.
"The mid-infrared image really focuses on the dust that's being heated up by new star formation.
"When you look at the Hubble images or any previous optical images, you don't really see all the dust that's being heated up."
Wispy filaments mostly made out of silicate dust connect the outer and inner rings.
At the centre of the bright core is a supermassive black hole that is devouring material that falls too close to it, and blasting out radiation.
Earendel, the 'dawn star'
Earlier this year, Hubble snapped what is thought to be a star that formed about 900 million years after the Big Bang.
The "star" was dubbed Earendel, meaning "morning star" in Olde English (it's also a character in J.R.R Tolkien's The Silmarillion.
Now the "star", in the constellation of Cetus, has been imaged again by the JWST.
Earendel is estimated to be about 50 times the mass of the Sun and millions of times as bright, but is so distant it appears as a small dot in a line (see details in the inset) stretched by the gravity of the cluster in front of it.
But we still don't know that much about it.
Dan Coe, one of the team members from the Space Telescope Science Institute, says the team is likely to release more information about Earendel this week.
The earliest galaxies after the Big Bang
It may not look like it but this blob, and others like it, are perhaps the most mind-blowing of all.
Galaxies within the first billion years following the Big Bang are expected to be small and rare.
But already, GLASS z13 is one of a number of potential galaxies from the early universe being put forward by different teams.
Each team is looking in a different part of the sky:
- some teams are looking into the area dominated by the SMACS 0723 galaxy cluster;
- the GLASS team, which includes Professor Glazebrook, are looking at a patch of sky dominated by another cluster known as Abell 2744 or the Pandora Cluster;
- and another team is scanning an area in the northern sky.
While we refer to distance to nearby galaxies in terms of light-years, calculating distance to earlier galaxies is much harder due to the expansion of the universe.
Instead, astronomers refer to early galaxies by their red shift – the amount that light has been stretched into the longer red wavelengths.
GLASS z13, for example, has a red shift of 13 – that roughly corresponds to the galaxy appearing as it did around 329.8 million years after the Big Bang.
Early galaxies in Professor Glazebrook's data are around a red shift of 12 – that's 370 million years after the Big Bang.
One of the candidates proposed by another team was calculated to have a red shift of 20 – that's a staggering 180 million years after the Big Bang.
"A lot of the community are thinking 'what the hell?'" Professor Glazebrook says.
Anything beyond a red shift of 15 – 270 million years post-Big Bang – is pushing beyond our models of how galaxies could form.
And already many of the galaxies have been disputed.
The technique used to measure these galactic candidates, known as photometric red shift, is reliable for younger galaxies, even those that formed in the adolescent years of the cosmos, Professor Glazebrook says.
But, he says, it is "ambiguous and imprecise", for the earliest galaxies at the extreme end of the range.
To really pin down the ages and composition of these galaxies, Professor Glazebrook says we need to analyse the chemical signature — or spectra — of the light coming from them.
He predicts we will have an answer soon.
"I reckon we'll know in a few months," he says.
