An international team of researchers has published the results of a study of how galaxies have clustered throughout the history of the Universe. They coincided with the predictions of Einstein’s general theory of relativity (GTR), confirming its validity.
Gravity shaped the cosmos. Its influence turned tiny changes in the amount of matter present in the early Universe into the giant strands of galaxies we see today. To test how gravity behaves on very large scales and how well its behavior agrees with the provisions of GTR, astronomers used the Dark Energy Spectroscopic Instrument (DESI).
DESI is a modern instrument capable of capturing light from 5,000 galaxies simultaneously. It is mounted on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory. The experiment is now in its fourth year of five, and by the time it is finished, it plans to study about 40 million galaxies and quasars. The data collected is processed by a collaboration of 900 scientists from more than 70 scientific institutions around the world.
As part of the study, astronomers used DESI measurements to map nearly six million galaxies over 11 billion years of cosmic history. This allowed them to study how galaxies have clustered over time, investigate the growth of cosmic structure, and thus provide one of the most rigorous tests of GTR in history.
Einstein’s calculations have passed the test. Scientists have found that gravitation behaves as predicted by GTR. This result confirms our leading model of the Universe and constraints possible theories of modified gravity proposed as alternative ways to explain unexpected observational results, such as the accelerating expansion of the Universe, which is usually attributed to dark energy.
The study also allowed us to clarify the mass of the neutrino, the only fundamental particle with a mass that has not yet been accurately measured. Previous experiments have shown that the sum of the masses of the three types of neutrinos should be at least 0.059 eV/c2 (for comparison, the mass of an electron is about 511,000 eV/c2). DESI results showed that the sum should be less than 0.071 eV/c2, which leaves a narrow window for the neutrino mass.
The results of the study are also consistent with the earlier suggestion that dark energy can evolve over time. The DESI collaboration will continue to analyze data from the first three years of observations and plans to present updated measurements of the dark energy and expansion history of our Universe next year.
Provided by NOIRLab
