A universe expansion rate calculation based on galaxy distances points to a younger universe

The galaxy NGC 4414 (Image University of Oregon)
The galaxy NGC 4414 (Image University of Oregon)

An article published in “The Astronomical Journal” reports a calculation of the universe expansion rate based on the so-called Tully-Fisher relation, an empirical relationship between the intrinsic brightness of a spiral galaxy and its asymptotic rotation velocity. Professor James Schombert, Stacy McGaugh, and Federico Lelli used the accurate distances of 50 galaxies as a guide to measure the distances of 95 other galaxies and then use those measurements to obtain a measure of the so-called Hubble Constant which has a peak of probability at 75.1 kilometers per second per megaparsec. This measure is very different from those obtained with other methods and, as a consequence, indicates that the universe is approximately 12.6 billion years old compared to approximately 13.8 billion obtained from other research.

In recent years, various teams of scientists used different approaches to calculate the value of the Hubble Constant, as the expansion rate of the universe is called. The aim is to obtain an increasingly precise value and therefore some other answers to the cosmological questions still under investigation. However, these studies are bringing more questions than answers because the proposed results are significantly different, incompatible with each other even taking into account the margins of error. For some time there has been talk of a tension in the world of physics due to these uncertainties that show that our knowledge of the universe is incomplete.

This time, three researchers used a new approach based on the empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation velocity or emission line width. This relationship, called the Tully-Fisher relation, is independent of the Hubble Constant and was used using the distances of 50 galaxies from the Photometry and Accurate Rotation Curves (SPARC) database as a guide. Those data were used to accurately measure the distances of 95 more galaxies.

Based on all the data collected regarding the galaxies examined, the researchers calculated the expansion rate of the universe at 75.1 ± 2.3 kilometers per second per megaparsec. The value is high compared to most of those calculated by other methods. According to the researchers, there is a 95% probability that values ​​below 70 can be ruled out, and there are several of them. Such a high speed also means that the universe is around 12.6 billion years old, but according to other research, it’s almost 13.8 billion years old.

Each new result concerning the Hubble Constant brings new discussions, especially when it’s absolutely incompatible with others obtained with other methods. Comparisons and analyzes of the results help to understand where the measurements may contain errors due to an incomplete knowledge of the universe. That’s a really complex problem, but eventually, the results of the research could be remarkable.

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