In our universe, there are various large and small “the galaxy” exists innumerably. How were these galaxies formed?
Immediately after the birth of the universe, there were no stars, let alone galaxies, and there were only hydrogen and helium gases. The density of the gas is uneven, albeit slightly, and the denser parts have a higher density of matter than the other parts, so the gravity is stronger. The gas attracted by the gravity of the dense part clumps and attracts more and more matter. When the clump of gas grows to a certain extent, a star will begin to form.
Similarly, the distribution of stars that have been formed around the universe also has high and low density parts. Stars in the denser parts coalesce to form early galaxies. Its shape is irregular, and its total mass is expected to be much smaller than today’s galaxies. It has been a common understanding in astronomy for many years that after a certain amount of time, a galaxy with the size and structure of today, with a spiral structure on the outside and a supermassive black hole in the center, was born. .
Observation results and simulations can narrow down to some extent how long the history of galaxy birth and evolution progressed. For example, the gas mura and total mass that existed immediately after the birth of the universe can be narrowed down by direct observation of the cosmic microwave background radiation, which is the first light in the observable universe, and the early universe. Because the speed of light is finite, observing the distant universe means observing the universe closer to the moment of its birth.
However, there are various difficulties in directly observing and studying galaxies in the early universe. The farther away an object is, the darker it appears. Also, as the universe expands, the wavelengths of light are stretched, and by the time the visible light emitted from the galaxy reaches the earth, it is biased toward infrared wavelengths, which are difficult to observe on the ground. In particular, the wavelength (364.6 nm = 0.3646 µm) where the “Balmer discontinuity”, which is important for determining the mass of galaxies, can be seen exceeds the infrared wavelength of 2.5 µm, which is difficult to observe. Masses could only be determined for galaxies one billion years from now. Already in this era, it has been confirmed that galaxies with masses 100 billion times the mass of the Sun, which can be seen in the present universe, exist.
Operation started in July 2022James Webb“One of the primary missions of space telescopes is to explore the mysteries of the early Universe. The James Webb infrared telescope is well suited for exploring wavelength regions that have been difficult to observe so far. The first observation results were released on July 12, 2022, and included a huge number of spectroscopic observations at wavelengths from 1 µm to 5 µm, which are said to contain information about the early universe.
【▲ Figure 1: Six “too heavy” galaxies discovered this time. The galaxy numbered 38094 in the lower left has a mass similar to that of the Milky Way, but a diameter of only about 1/30 (Credit: NASA, ESA, CSA, I. Labbe (Swinburne University of Technology), ID is the author ( Added by Riri Ayane)]
A research team led by Joel Leja of Pennsylvania State University analyzed this spectroscopic data and found thatAt least 6 galaxies found to be ‘too heavy’ than expected. These galaxies existed 500 to 700 million years after the birth of the universe (redshift 7.4≦z≦9.1).Estimated mass is more than 10 billion times that of the SunThat’s what it means.One of them could even have 100 billion times the mass of the Sun. (※) . this is,Up to 100 times heavier than previously modeled massesis. It was unexpected to find such a massive galaxy when only the first 3% of the history of the universe had passed, and Leja et al. It turned out to be unlikely.
*…The mass of the galaxy numbered 38094 is estimated to be 77.6 billion times the mass of the Sun at its most probable value and 129 billion times its maximum value.
【▲ Figure 2: Details of 6 galaxies (Credit: NASA, ESA, CSA, I. Labbe (Swinburne University of Technology), table by the author (Riri Ayae))】
Leja and colleagues informally refer to these galaxies as “universe breakers (universe breakers). Existence of “Universe Breakers” does not match 99% of cosmological models built so farSo, in a sense, this naming is apt. Universe Breakers shows that either cosmological models or our understanding of how galaxies form can be fatally flawed, but whatever corrections may be necessary, the way we think about the universe is going to change. It may have to be radically revised. And this review has the potential to change not only the early universe, but also our understanding of the present and future universe.
Source
- Ivo Labbé, et.al. “A population of red candidate massive galaxies ~600 Myr after the Big Bang”. (Nature) (arXiv)
- Adrienne Bernard. “Discovery of massive early galaxies defies prior understanding of the universe”. (The Pennsylvania State University)
Text: Riri Ayae
