It is called GN-z11, and we have known of its existence since March 2016, when the Swiss astronomer Pascal Oesch published in The Astrophysical Journal his great discovery: the farthest galaxy in the known universe , located 32 billion light years from the Earth. It is so far from us that we see it as it was 13.4 billion years ago, just 400 million years after the estimated date of the big bang. That, in cosmic terms, is barely a quarter of an hour after the origin of the universe. But what does a galaxy look like at that moment so early?
Scientists do not stop investigating it. In December 2020, the team of Chinese astronomer Linhua Jiang, from Peking University (China), announced a highly controversial finding about this mystery: after analyzing all the GN-z11 data obtained in April 2017 from the Keck observatory in Hawaii (USA), Linhua discovered that the galaxy had increased in size , and that within three minutes it had become hundreds of times brighter. What had happened? The Chinese astronomer proposes a solvent theory to explain it: that young galaxies have a much greater activity than previously thought. And this can change our understanding of how the early universe born after the big bang was shaped, a phase in the history of the cosmos that right now is a thick blanket of shadow for human knowledge.
“We should have chosen a better name for this galaxy, a funnier one,” jokes Pascal Oesch, the discoverer of GN-z11, in a statement to VERY. GN comes from GOODS-North, which is what its location in the field of galaxies is called, and z11 appeals to its redshift, which is the indicator of the distance that separates it from us ”. GN-z11 is located in the constellation of the Big Dipper, an old acquaintance of civilization, also commonly called the Main Car.
The discovery of GN-z 11 is yet another of those made with the Hubble telescope . To detect this galaxy, Oesch and his team used the WFC3 –Wide Field Camera 3– camera, installed in May 2009 in the fourth repair mission that NASA sent to this thirteen-meter-long, eleven-tonne telescope that floats. 590 kilometers from us. The camera, developed by NASA’s Goddard Space Center in Washington, sees large areas of the electromagnetic spectrum invisible to human eyes. So WFC3 is Hubble’s eye for very distant and tiny galaxies. NASA has christened this Hubble program for tracking and observing the cosmos as the deep survey of the origins of the great observatories –Great Observatories Origins Deep Survey (GOODS) -.
” GN-z11 is a very young galaxy,” Oesch explains. It is about a hundred times less massive than our Milky Way and is twenty-five times smaller than it. However, it is forming stars at a rate twenty times higher than the Milky Way. In general, the galaxies at that time were still in a very fast growth phase, so they very quickly converted their gases into stars, which is the way to generate more and more mass ”.
“The curious fact – adds Oesch – is that the galaxy had actually been seen some years before by two Hubble instruments. However, due to its high luminosity, it was thought that it would be a much closer galaxy ”. When the Swiss team observed it in 2015, that same year, thanks to the Keck telescope in Hawaii, the recorded galactic distance record had been surpassed several times. “When we finally measured GN-z11, it turned out to far outperform the farthest known light source, the EGSY8p7 galaxy, with a much smaller redshift of 8.68,” says Oesch. That is, we see it now as it was about 13.2 billion years ago, almost at the beginning of everything.
As soon as the WFC3 camera on Hubble became operational, Oesch’s team detected the galaxy, although at the time it was nothing more than a light source. You had to work on the data that arrived to confirm it. “GN-z11 was part of a sample of four galaxies that appeared to be on a redshift of z = 10, which was the distance from the farthest known sources up to that point. Of all of them, GN-z11 was the brightest of all and that is why we focused on it ”, recalls Oesch. When they obtained the data that led to their final measurement, the omens were confirmed. And by far. “The distance turned out to be even greater than what we had originally estimated from the images taken, which made this galaxy truly unique. We had not expected to find a light source at such a distance, at the very limits of Hubble’s capacity ”, acknowledges the Swiss astronomer.
In the 21st century, we simply say: Hubble has discovered a galaxy. But the reality is much more complex than that mere phrase. Hubble collects electromagnetic radiation – light is one of them, but not the only one – in different spectra – visible, infrared and ultraviolet – and, based on these data collected from a corner of the universe, scientists they have to get to work –analyzing, debugging and translating them– to reach a concrete conclusion about what this telescope has seen and obtain the final photograph. It is a process of months and years; And it is not only technological, but it is based on the scientific knowledge accumulated for at least almost four centuries.
In the measurement of distant galaxies the concept of the redshift is essential , but what does it mean? This story could begin with Isaac Newton (1642-1727) and his investigations into the spectra of sunlight, which Newton decomposed with a prism to analyze them. The fundamental finding came in 1842 with the so-called Doppler effect, named for the Austrian scientist who explained it, Christian Doppler (1803-1853). This effect consists in that the noise of a vehicle is heard higher when it comes towards us and more serious when it moves away, once it has passed our position. Doppler discovered that this is due to the action of the noise-emitting body – the vehicle, in this example – on the wavelengths of the sound it emits as it travels. The Doppler effect, applied to the cosmos, would revolutionize the history of astronomy.
Albert Einstein overthrew the Newtonian approach by publishing his general theory of relativity in 1914, which he completed three years later by adding the cosmological constant to ensure that the universe was static and finite, as he thought it should be, although applied mathematics in their theory would point to the contrary.
From there, the story continues on the other side of the Atlantic. At the Flagstaff Observatory (Arizona), the astronomer Vesto Slipher (1875-1969) was going to combine spectrometry – remember Newton and his prism? – and the Doppler effect. Observing the Andromeda nebula – they called it that nebula, because they did not yet know it was another galaxy – Slipher realized that light from the universe travels towards us in short or long wavelengths. In the case of Andromeda, these were shorter wavelengths, so that light tended towards the blue color when analyzed in a spectrometer – since the human eye cannot see in that range.
This is how Slipher realized that the same effect that Doppler had explained for sound waves operated in space : the body emitting any electromagnetic radiation –among them, light– alters the wavelength of said radiation and this influences in the color with which we receive it. So a shift of light towards blue indicates that the object emitting it is moving towards us . Slipher thus discovered that the Andromeda galaxy is approaching the Milky Way; in fact, NASA estimates that the collision between the two will occur in about 4.5 billion years.
But the most revealing thing was that Slipher also came to the opposite conclusion: a shift of light towards red, absolutely the majority when observing the universe from Earth, indicates a longer wavelength, and, therefore, that the The object that emits them moves away from the observer , that is, from the Earth. But it is not about the object itself moving away by its own motion: it moves away because said body inhabits an expanding universe. The cosmological constant was in tatters. The universe was neither static nor finite, as Einstein had believed. It was dynamic. And it expanded.
The final blow would come shortly after, at the hands of the man whose surname ended up naming the telescope that found the GN-z11: Edwin Hubble (1889-1953). From his observatory on Mount Wilson, in California, he discovered that the velocity of the galaxies was proportional to the distance between them; that is, the further they are, the faster they travel. It is the so-called Hubble law. The American astronomer continued with the reasoning and concluded that, if that kind of tape of the universe were rewound, the origin of everything would have to be the same point from which everything would have begun to expand: the big bang. The last and most accurate measurement of the big bang was made by NASA’s COBE satellite, which operated between 1989 and 1993. The project, for which John C. Mather and George F. Smoot were awarded the Nobel Prize in Physics in 2006, established that the universe is the biblical non-biblical figure of 13.8 billion years.
So that signals, radiation, reach us from the cosmos. If the light of these electromagnetic radiations shifts towards the red, they come from an element that is moving away. By analyzing the intensity of that red, it is possible to calculate how far the object is, a trip that not only occurs in space, but also in time, because that light takes time to reach us. When Oesch discovered GN-z11, that redshift of 11, translated into common parlance, means that we see this galaxy not as it is now, but as it was 13.4 billion years ago, 400 million years after the big bang. To look toward GN-z11 is to look toward the newborn universe, since astronomers believe that stars formed just 100 million years after the big bang .
That fledgling universe might not be as dormant as has been thought so far. The discovery of GN-z11 was a signal about this theory, which has recently been reinforced with the finding cited at the beginning of the report, that is, the one made by Linhua on this distant galaxy. Linhua argues that young galaxies – and therefore the universe in that more or less initial stage – have a much greater activity than is thought.
In two articles published in the December 2020 issue of Nature Astronomy , Linhua and his team revealed that they had detected a gamma-ray burst originating from GN-z11. These bursts are the most powerful explosions in the universe: some of them release more energy in just ten seconds than the Sun would emit in 10 billion years. And as is often the case with many great discoveries, it all happened by chance. “We looked at GN-z11 in April 2017, but our goal was not to find any gamma ray bursts, because the probability of doing so is extremely low,” Linhua explains to VERY. Our purpose was to detect some emissions from the galaxy to try to make a more accurate measurement of its redshift, and thus try to refine more about how far away it is.
“During the observation,” continues the Chinese scientist, “by pure chance, we captured a burst of gamma rays from GN-z11. We did not notice this until a week later, when we analyzed the information collected. ” In fact, what Linhua’s team found was not direct gamma radiation, but a remnant of it. “Gamma rays can only be detected with space satellites [since they are absorbed by Earth’s atmosphere], and we did the observation from the Keck Observatory in Hawaii.”
What the observatory’s spectrometers captured was a near-infrared burst with an observed duration of less than 245 seconds, as revealed in one of the articles published in Nature. In it, Linhua assures that some gamma ray bursts are associated with bright ultraviolet flashes. But hadn’t Linhua’s team received infrared rays? The gamma explosion in the galaxy would have emitted ultraviolet radiation, but, due to the Doppler effect, “and due to the expansion of the universe, it would have reached Earth converted into infrared radiation, which was detected by the Hawaii observatory”, explains the expert. Again Newton, Doppler, Slipher and Hubble.
To confirm that they were correct, Linhua’s team verified that the signal came from space and not from Earth. Later, after ruling out the possible artificial origin of this infrared radiation – a satellite, for example – they concluded that the origin of the signal had been a remnant of ultraviolet rays from a gamma ray burst. This had been produced on GN-z11, and they had seen it live, which is almost miraculous.
The finding may be of momentous importance, as Linhua explains: “ Gamma-ray bursts are associated with massive stars, twenty to thirty suns in size . When we see such an explosion, it means that one of those stars has died. They run out of core fuel and gravity causes them to collapse. The blast is so powerful that it can be seen at enormous distances. When you observe something like this, you have proof that there were already such stars in that observed period ”.
Astronomers think that the first stars formed between 100 and 150 million years after the big bang, and that the first galaxies began to generate about 100 million years later. Therefore, GN-z11 would not be a first generation galaxy. In fact, Linhua’s team discovered in their observation that some emissions received from the galaxy had their origin in gas with doubly ionized carbon and oxygen, suggesting a great abundance of metals, elements that would not contain first-generation galaxies.
This is also the time when the seeds of the first supermassive black holes began to form and grow. Those mysterious astrophysical objects gradually reionized the universe. “Our finding,” Linhua explains, “means that the physical conditions of that particular galaxy, or at least some of the very distant galaxies, could be different from those with a lower redshift, that is, those found closer to the Milky Way. But we need future telescopes to fully understand these types of galaxies, which are too faint and too far away for the capacity of current observatories ”.
The space telescope that is called to revolutionize this look is the James Webb, whose launch is scheduled by NASA for December 18, 2021. It will be located 1.5 million kilometers from Earth, so far away that, contrary to As with Hubble, astronauts cannot be sent to repair it. In return, the James Webb, due to its privileged location and the power of its equipment, will offer humanity the best views of the universe that it has ever had. “When it is deployed, astronomers will be able to search much further and deeply, and therefore, we will find a lot of galaxies at the same distance as GN-z11 and even further away,” says Oesch.
But how far? How close to the big bang will it be possible to observe from close to the Earth if the necessary technology is available? “It is an aspect that is not clear yet – explains Oesch -, it will depend on how quickly the populations of galaxies formed in the early universe. Current estimates estimate that we might be able to see up to 300 million years after the big bang. ” If the cosmos were a centennial person whom we have just met, that data would be equivalent to being able to use a camera to see from the present the life of its previous 98 years.
