Mysterious discrepancy in Hubble constant allegedly before resolution after all
The debate surrounding the Hubble constant continues: While many see a growing discrepancy, one astronomer insists there is no such thing.
(Image: Yefym Turkin / Shutterstock.com)
A research team from the USA is convinced that new data from two space telescopes resolve the stubborn discrepancy in fundamental measurements of the expansion speed of the universe. The group led by astronomer Wendy Freedman from the University of Chicago has now determined a value of 70.4 kilometers per second per megaparsec for the so-called Hubble constant – with an inaccuracy of 3 percent in both directions. This brings the value determined for the nearby universe into statistical agreement with the 67 km/sec/Mpc (with 0.7 percent inaccuracy) that was determined for the beginnings of the cosmos using the Planck space telescope, the team explains.
Working to resolve the discrepancy
(Image:Â Freedman et.al)
With his work, Freedman once again wants to resolve the so-called Hubble discrepancy, which has puzzled astronomers for years. The issue here is that new measurements are constantly finding values for the expansion speed of the cosmos for comparatively close galaxies that do not match those from the early days of the cosmos. It was only in January that a research team declared that a new measurement had even turned the “Hubble tension” into a “Hubble crisis”, so great was the discrepancy found. Freedman sees things differently. For years, she has been convinced that increasingly precise measurements will eventually resolve the discrepancy. This will happen in the coming years, she now believes.
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Freedman and her team have doubled the number of galaxies used to calibrate the measurement of supernovae. This is the only way to measure such large distances or their change due to the expansion of the universe. Measurements from the Hubble and James Webb space telescopes were evaluated for this purpose. Nevertheless, the discrepancy between the new value and the value of the Planck space telescope, which is considered the gold standard, is still large. Moreover, the value now presented in the Astrophysical Journal is somewhat larger than one that Freedman determined four years ago. Even then, she predicted an end to Hubble's voltage. Now the discrepancy is also somewhat greater for her.
The Hubble constant (H0) is a fundamental quantity in cosmology. The value indicates the speed at which an object at a distance of one megaparsec (3.26 million light years) is moving away from us due to the expansion of the universe alone (the Andromeda Galaxy, for example, is around 0.89 megaparsec away from us). The constant was first calculated by the US astronomer Edwin Hubble, whose name it now bears. Although the measurements have become increasingly precise in recent years, they have not provided a consistent value. Instead, a mysterious discrepancy has emerged that has become one of the most exciting questions in cosmology today.
(mho)
