Webb telescope discovers mysterious galaxies that shouldn't exist

In February 2023, Nature magazine announced an important discovery of the Webb telescope, that is, it discovered some high-redshift galaxies that should not exist. The mass of stars in these galaxies is so large that it is enough to overturn our existing understanding of the universe. Why can the massive stars that existed in the early days reshape our view of the universe?

To talk about these galaxies, we need to start with our understanding of the universe. The Big Bang cosmological model believes that the universe was formed by the expansion of a dense and hot singularity after a big explosion 13.8 billion years ago. Its proposal is actually based on a series of observational evidence. In 1924, American astronomer Hubble first discovered that the distance between the Andromeda Galaxy and our earth at that time was larger than the scale of the Milky Way we know, so he proposed that the Andromeda Galaxy is actually a galaxy located outside the Milky Way. After that, Hubble continued to discover more extragalactic galaxies. He not only discovered more extragalactic galaxies, but also discovered an amazing phenomenon, that is, the farther the galaxy is from our Milky Way, the faster it moves away from our Milky Way. This is what we now know as Hubble's law.

Based on this observational foundation, American physicist Gamow formally proposed the Big Bang model of the universe in 1946. At the beginning of the explosion, matter could only exist in the form of basic particles such as neutrons, protons, electrons, photons and neutrinos. The continuous expansion of the universe after the explosion caused the temperature and density to drop rapidly. As the temperature dropped and cooled, atoms and molecules gradually formed and compounded into ordinary gases. The gas gradually condensed into nebulae, which further formed various stars and galaxies, and finally formed the universe we see today.

In 1964, Penzias and Wilson of Bell Telephone Company in the United States unexpectedly received a kind of radio interference noise when debugging a huge horn-shaped antenna. The signal strength in all directions was the same and it did not change for several months. After hard work, they later learned that this was the relic left over from the Big Bang of our universe.

In the 1970s, American astronomer Vera Rubin proposed the existence of dark matter by observing the movement of stars in nearby galaxies. More than 20 years later, scientists in the United States and Australia discovered that our universe is not slowing down, but expanding at an accelerated rate. Based on this observation, they further proposed the existence of dark energy in our universe. Because of dark energy, the universe has been expanding at an accelerated rate since 6 billion years ago. This is the basic common sense of cosmology that we currently know.

Solar system, picture from Tuchong.com

So the composition of our universe, according to our understanding, should include three types: normal matter, dark matter and dark energy. As for the stars and galaxies in our universe, according to our understanding, they also went through a process from nothing to something. Because the temperature was very high for a period of time in the early universe, there were no stars and galaxies. Only in the later period, as the universe expanded, the gas temperature gradually decreased. The current cosmic model believes that stars and galaxies are formed, but galaxies are relatively small at the beginning. Because of the collision between galaxies, galaxies become larger over time. So we can see that it has also gone through a process from small to large, which is what we now think of as the cosmic model. It is one of our goals to always understand the early universe. So in 2021, the Webb telescope, which can see the early universe, was launched.

The Webb telescope observations found that when the universe was only 3% of its current age, as we expected, the mass of galaxies should have been very small, but the mass of stars in the discovered galaxies is 10 billion times that of the sun, and even the mass of stars in a galaxy may be 100 billion times that of the sun, close to the mass of the Milky Way. Scientists have discovered a total of 6 similar galaxies, which may change humanity's understanding of the origin of galaxies in the universe. Scientists call these galaxies "breakers of cosmic rules" and they contradict 99% of existing cosmic models. They speculate that some may be supermassive black holes, but it seems unlikely to find 6 black holes at the same time, and some of them may be real galaxies.

The mass of the stars detected in the new study is 100 times greater than scientists previously thought. According to science, such galaxies should not have grown so large so soon after the birth of the universe. We thought we would only find tiny, young baby galaxies at this point in time, but we found galaxies as mature as our Milky Way at what was previously considered the dawn of the universe. Of course, more observations are needed to verify this observation.

If these galaxies can be further confirmed, it means that our understanding of the history of the early universe may be wrong, and galaxies evolve much faster than humans realize. This requires changing the previous cosmic model or changing our understanding of the origin of galaxies.

This article is a work supported by Science Popularization China Starry Sky Project

Author: Gou Lijun (Professor at University of Chinese Academy of Sciences)

Reviewer: Han Wenbiao (Researcher at Shanghai Astronomical Observatory, Chinese Academy of Sciences)

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.