Astronomers measured the amount of helium from the first minutes after the Big Bang
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- Astronomers measured the amount of helium from the first minutes after the Big Bang
To understand how the universe originated and evolved, scientists study not only distant galaxies and stars, but also chemical elements formed at the earliest stages of cosmic history. Their number stores information about temperature, density, and physical laws that were in effect shortly after the Big Bang. Astronomers were able to measure the content of primary helium with an accuracy significantly exceeding previous estimates. How the chemical composition of ancient galaxies helps to uncover the secrets of the early universe is described in the Izvestia article.
Traces of the first minutes of the Universe
Researchers, including specialists from the University of Minnesota, measured the amount of helium formed in the first five minutes after the Big Bang. The results are presented in five publications in The Astrophysical Journal (AJ).
For the work, the scientists used a large binocular telescope and conducted a total of 130 hours of observations. They studied 15 small, distant galaxies, whose chemical composition has changed relatively little since their formation. This allowed the researchers to obtain information about the substance that preserved the features of the early universe.
As a result, the uncertainty of measuring the primary helium content was reduced to 0.5%. This is about three times more accurate than the previous estimates. This precision gives scientists the opportunity to verify existing ideas about the early stages of space history and about the physical conditions that determined the formation of light elements.
Evan Skillman, Distinguished Professor at the University of Minnesota School of Physics and Astronomy
This is a large-scale physics experiment and one of the most significant discoveries in my entire 40-year career. This is a fundamental number that specifically tells us about the conditions of our universe in the first five minutes of its existence.
Why do scientists study helium?
According to the Big Bang theory, the universe began to expand from an extremely hot and dense state about 13.8 billion years ago. In the first minutes after the expansion began, light chemical elements were formed, including helium and deuterium. Their initial number depended on the physical conditions that existed at that time.
The amount of primary helium is one of the important ways to test the Big Bang theory. Other evidence is the continued expansion of the universe and the cosmic microwave background radiation, which has survived to this day from the early universe.
Previously, astronomers often estimated the initial helium content by observing many galaxies and calculating what the chemical composition of matter was before subsequent generations of stars changed it. However, this approach required extrapolation, and it could introduce additional uncertainty.
In the new work, the researchers focused on 15 particularly little-changed galaxies. Since their substance has undergone a relatively small chemical evolution, they act as a kind of cosmic time capsules. Studying them allows us to accurately estimate how much helium existed in the early universe.
How was the accuracy improved?
For the analysis, astronomers used MODS spectrographs developed with the participation of the Ohio State University. These devices allow you to study the radiation spectrum and determine which chemical elements are present in the observed objects.
The team simultaneously studied more than 10 spectral lines of helium and 15 lines of hydrogen. The comparison of the signals helped to detect and correct small sources of error that were difficult to account for in previous studies. For measurements with an uncertainty of less than 1%, even such minor effects can significantly affect the final result.
The development of the spectrographs took 12 years, from the initial idea to the first observations of the sky. According to Richard Pogge, Distinguished Professor of Astronomy at Ohio State University, the instruments were created specifically to solve such problems related to measuring the fundamental characteristics of the universe.
What does helium tell us about the laws of physics
New measurements are important not only for clarifying the chemical composition of the early universe. The amount of helium formed after the Big Bang depends on the conditions in which the first nuclear reactions took place, including the number of types of elementary particles that existed at that time. Using refined data on helium, the researchers were able to calculate the number of neutrino families in the early universe.
Neutrinos are extremely light subatomic particles that interact weakly with matter, but play an important role in modern concepts of fundamental physics.
The results obtained make it possible to more accurately verify the Standard Model of elementary Particle Physics, a theory describing known fundamental particles and their interactions. Comparing calculations with astronomical observations helps scientists figure out how well this model describes the conditions that existed in the first minutes after the Big Bang.
The work does not refute the Big Bang theory, but clarifies one of the important parameters used to verify it. The more accurately researchers measure the amount of primordial helium, the more strictly they can check the physical models of the early Universe and look for possible discrepancies between calculations and observations.
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