Is that the brake light of a car? The burning tip of a cigarette maybe? Or an extremely zoomed-in photo of the standby button on a television? Match the blurry red clumps of angular pixels with the spectacular James Webb space telescope images published in mid-July, images of gracefully fanned out nebulae and razor-sharp galaxies, and you’ll soon be shrugging.
And yet it is precisely those hazy specks that, much more than the mesmerizing cosmic vistas that previously made the news, are now causing increasing excitement among astronomers worldwide.
If the first signs don’t deceive, these red pixel collections reveal the most distant galaxies humanity has ever seen. The galaxies you see here – extremely young variants of the Milky Way in which we spend our cosmic lives – have been captured on camera as they appeared only a few hundred million years after the Big Bang. And while that sounds long by human standards, that time pales in comparison to the nearly 14 billion years the universe has been in existence. The systems in the photo are, in short, very young. Some may even be among the very first galaxies to appear in the Universe.
Those cosmic baby photos let you sink wonderfully into the enchantingly deep time of space, dizzyingly long periods of time that make human lives pale. Still, these galaxies aren’t just dreamy discoveries or amusing additions to the astronomical record books. No, they are also of considerable scientific interest.
Such very young galaxies can reveal how the evolution of these cosmic objects takes place. Compare it with biologists who have so far only seen the adult specimens of an animal species and then suddenly discover the baby phase. Whether life started in an egg, as a floundering little version of the adult animal, or whether you see a caterpillar before it develops into a butterfly: it makes a difference.
It is the same in the cosmos. And if the first tentative finds are not deceiving, several indications are already emerging that astronomers will soon have to adjust the prevailing view of the evolution of those galaxies, from the moment of the Big Bang to the present.
‘It is really unbelievable what the international community has already found in the first two weeks since these data became public’, says astronomer Mariska Kriek of Leiden University. “We already knew the James Webb would reveal groundbreaking things. But now we see it for real. And it certainly doesn’t disappoint.’
Low hanging fruit
The James Webb space telescope, the new flagship of international astronomy, is the ‘successor’ to the Hubble space telescope and was built, among other things, to peer deeper into the cosmos than ever before. That is why he does not look at ‘normal’ light, but at heat radiation invisible to the human eye. Light coming from deep in space is stretched along the way. What was visible light long ago – with a shorter wavelength – therefore arrives here as thermal radiation, which has a longer wavelength.
To pluck that heat radiation from the cosmic depths, the telescope’s bottom is covered with a sun shield, the size of a tennis court, that keeps it cold. Partly because of this, Webb is so sensitive that, if he were on Earth, he could measure the heat radiation of a bumblebee on the surface of the moon.
It was obvious that this astronomical superpower would lead to spectacular discoveries. And yet astronomers around the world have been going from one surprise to the next since the telescope started collecting its data. ‘I don’t think any of us would have foreseen that we would see so many galaxies at such a great distance. We expected some surprises, but not so quickly or so drastically,” University of California astronomer Guido Roberts-Borsani said last week. against the popular science weekly New Scientist.
‘We are already picking the low-hanging fruit’, summarizes Kriek these first weeks. And although there is much more, and above all much more beautiful, fruit than astronomers had dared to hope for, it is now mainly a matter of working hard: analyzing as much measurement data as possible, recording everything neatly and describing it in specialist articles.
It is not yet time to separate the wheat from the chaff. ‘That is why we have to be very careful’, warns astronomer Karina Caputi of the University of Groningen, an expert in the field of very distant galaxies. All results that came out during the first two weeks have so far only been published on the scientific pre-publication site Arxiv. Only when other astronomers have critically studied these articles and assessed them as satisfactory – so-called peer review – do they end up in mainstream journals. And even then, we’re not quite there yet, Caputi says. “The distance still has to be confirmed for all these galaxies.”
redshift
Experts such as Caputi determine the distance of distant galaxies using what is known as redshift, a technical term that refers to the fact that distant galaxies appear redder than closer ones.
That’s right. Due to the expansion of the universe, distant galaxies are moving away from us faster. Light moving away from you changes color like the siren of a speeding ambulance changes tone. And what tone is to sound, color is to light: that is why faster-moving and thus more distant galaxies appear redder than closer ones.
For the first, rough, distance determination, astronomers simply look at how red the galaxies are. Only: sometimes you accidentally draw the wrong conclusion. “A galaxy surrounded by a lot of dust can sometimes turn redder than it should based on its distance,” says Caputi.
It makes you have to look at the now found extremely distant galaxies again for confirmation, in a slightly different, more accurate way. If, for example, it is possible to make a spectrum of such a system – a signature of the colors present in the light of such a system – you can determine the redshift very precisely, and you do know the distance for sure.
“I therefore think that for the second observation round, which will probably start at the beginning of 2023, we will receive a lot of requests to perform verification measurements on extremely distant systems,” says Kriek, who was active in one of the panels that observation time on the James Webb. ‘For this first series of measurements, we had about four times as many requests as the available observation time. I think the competition will only get bigger from now on.’
Downright amazing
The finds of the first distant galaxies are not only surprising in number, the distances themselves are in some cases simply astonishing. If the most distant galaxy Hubble ever saw had a redshift of 11, which translates to an age of about 400 million years after the Big Bang, James Webb’s data has already identified dozens of candidates well beyond that.
For example, on July 19, red spot GLASS-z13 on, with an estimated redshift of 13. This will immediately sharpen the record – if the find holds up – by about 100 million years. Spectacular, were it not for the fact that James Webb has been breaking his own records over and over again lately.
Just look at the burning ash point of ‘Maisie’s Galaxy’, named after the discoverer’s daughter, at a redshift of 14. Or no, hey, stop: there are two systems again with a redshift of 16. One research group suddenly even found systems last week at a redshift of 20roughly 180 million years after the Big Bang. It is the preliminary record.
Caputi expects it will be difficult to break that record much further. “It was during that time that the very first galaxies formed,” she says. However, more and more galaxies in the sky are also less and less bright. “So it’s getting harder and harder to see them.”
The question remains whether what we now see is real, or whether it is a case of red-coloured illusion. “If even 20 percent of the galaxies are actually at the reported redshift, it’s strong evidence that these types of galaxies form very early and very quickly and become very massive and bright very quickly,” said astronomer Rohan Naidu of the Harvard-Smithsonian Center for Astrophysics about that New Scientist. It must therefore be quite difficult if the current findings are not to be left in the future.
Moreover, Caputi says: ‘The images in which these galaxies have been found are far from the deepest that James Webb is going to make of the universe. When I think about what we might have seen in six months… oh my god‘.
More massive, more regular, weirder
The first results of the James Webb space telescope do not only highlight the extremely distant galaxies. So suggests a new study that some galaxies are accumulating a lot of stars and mass sooner than expected. ‘If that’s true, we really have to go back to the drawing board’, says astronomer Mariska Kriek. Colleague Karina Caputi, however, believes little of it. ‘They use a new analysis method that has not yet been sufficiently tested,’ she says.
That is the problem with such studies: they are quickly written down and the critical check of colleagues is still missing. Yet they show the type of insights Webb can provide. This is how one group discovers more disk-shaped systems than before, the other that galaxies are more compact than predecessor Hubble saw, and a third reveals a strange, atypical galaxy that almost no heavy elements contains. It is the tip of an ever-increasing mountain of publications that can tilt the picture of the evolution of galaxies. And then the measurements of, for example, the atmospheres of distant planets still have to start for the most part.
‘It’s like being in a theater and until now you could only see the universe through the cracks in the curtain,’ says Kriek. “With Webb, those curtains opened. Now we suddenly see the entire stage.’