A recent study published in the scientific journal The Astrophysical Journal Letters reports the observation of the most distant space object ever detected so far. It is a galaxy called GHZ2, which was observed thanks to the James Webb Space Telescope (JWST), which has been operational for a few months with a mission to observe the deep universe.
The discovery was made by an Italian research group led by Adriano Fontana of the National Institute of Astrophysics, which is taking part in the Festival of Science in Rome (opening on Saturday, November 26 at the Auditorium).
Observing a galaxy billions of light-years away means going back in time: according to the scientists, the galaxy’s image dates back to “only” 350 million years after the Big Bang, which happened almost 14 billion years ago. Astronomers have also observed another galaxy that is slightly more recent, 450 million years after the Big Bang.
These are images of the very young universe, when stars and galaxies had just begun to form after the cooling of the primordial cloud of energy and particles.
“The light that arrives from those objects has traveled for many billions of years,” explains Fontana. “The light we observed was emitted over 13 billion years ago, when the universe was much younger. It’s like getting a letter from a very distant country: it arrives when things have changed in the meantime. Today, those objects have changed as well, if they still exist at all. So, the farther away we look, the further back in time we go.”
No one had observed the universe so close to the Big Bang…
Three hundred fifty million years after the Big Bang represents a very short time on the scale of the universe, when galaxies had just begun to form. There was a one in ten chance of finding something in the region of space we looked at.
I confess that, before we saw the data, we had already put together a draft of a scientific publication in which we would explain why we didn’t see anything. Instead, we observed no less than two galaxies, and that is the major discovery. It suggests there were more stars and galaxies at that time than we expected. As if something was helping the stars form in the early universe. But we still don’t know what.
There are two theories that are the most prominent. One is that the stars at that time were different from those we know today, like the Sun. There were fewer chemical elements, because there were no supernovae that generated the heavier ones.
Another possibility is that they were even more different than we think, and that, for example, they did not contain metals. In this case, they would be brighter and this could have facilitated the observation. Then, there is the hypothesis that would require a “new physics.”
Physical laws yet undiscovered?
It is possible that in the young universe there were primordial black holes, which would have provided the gravitational force necessary to accelerate the formation of complex structures such as galaxies. But the existence of primordial black holes presupposes physical mechanisms that are not predicted by the so-called “standard model,” the most accepted theory of elementary particle physics today.
Observing the universe in its initial phases allows us to see phenomena at work which are difficult to observe in its subsequent evolution, when others come into action to complicate the picture.
Your “record” is also due to a recent “recalibration” of the telescope that led to a revision of the preliminary results. What does that mean?
Once in orbit, a space telescope has to be calibrated with measurements on already known stars in order to check its sensitivity. The first JWST data arrived before this was done.
The data was based on calibrations done in the lab and had errors of 20-30%. Many of these observations were disproved after calibration: some galaxies disappeared and others emerged. The ones we observed, however, survived this revision.
Is the telescope delivering the results hoped for when it was launched?
The quality of the data is extraordinary. In the field of galaxy research, the results have come quickly because the information collected by the JWST is made public immediately. Different researchers can use it in competition with each other, and this speeds up the analysis. But it also has the advantage of providing verification of the findings: another research group was able to independently confirm our conclusions.
Other data from the telescope is owned by individual researchers for a year, which gives them the time to work on it in a more calm manner. So, more discoveries will come.
What are your goals now?
To study the spectrum of light that arrives from galaxies like these in order to discover their composition, temperature and manner of movement. In other words, the “colors” (i.e. the frequencies, because the James Webb Space Telescope observes infrared light that is not visible to the human eye) that make up the light emitted. This is the field in which the telescope is most innovative, with a sensitivity 1,000 times greater than previous instruments.
Nowadays, the fate of the International Space Station, a U.S.-E.U.-Russia collaboration, has to reckon with the war in Ukraine. Is there a risk of geopolitics getting in the way of the future of research?
The bulk of our missions involve only the E.U. and the U.S., so there are fewer problems. But there are still some: the development of the eRosita probe, a space telescope designed as part of a collaboration between Russia and Germany, is currently blocked.
The debate in the scientific community remains. Our view is that science should not be subject to the limitations dictated by politics, and that the distinction between political and individual responsibility should be reaffirmed.
I just came back from a conference at CERN in Geneva where the situation is dramatic, because in the field of particle physics the collaboration with Russian scientists was much stronger. Then, there is also China: there are several collaboration projects, and we will have to see whether the geopolitical situation will favor them or not.
Private entrepreneurs like Jeff Bezos or Elon Musk are getting into space exploration. Is this happening in the telescope world as well?
Little or not at all. Private companies are going into space research wherever there is profit: today, putting satellites in orbit or selling launches has become a profitable activity. From scientific missions like ours, there is nothing they can gain.
However, some of that also affects our field. For example, next year the European Space Agency will launch the Euclid satellite. It was originally supposed to use the Russian Soyuz launcher, but that is no longer possible. It could have used the French Ariane launcher, which costs much more and could have led to delays. In the end, to save money and time, it was decided to use the Falcon 9 rocket launched by Musk’s SpaceX.
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