A recent study conducted by the James Webb Space Telescope (JWST) has shed light on one of the biggest mysteries in cosmology – the expansion rate of the Universe. The findings, in agreement with measurements made by the Hubble Space Telescope, have not brought any clarity to the so-called Hubble tension.
The Hubble tension refers to the disagreement between different measurement methods used to determine the expansion rate of the Universe, also known as the Hubble Constant. Despite repeated measurements using different techniques, the results have consistently varied, leaving scientists searching for alternative methods to solve this cosmic puzzle.
The expansion rate, denoted as H0, is crucial in understanding the dynamics of the Universe. Different measurement methods have returned inconsistent results, with one method suggesting an expansion rate of around 67 kilometers per second per megaparsec, while another indicates a rate of around 73 kilometers per second per megaparsec. This discrepancy between the two measurements is what has come to be known as the Hubble tension.
Efforts to reduce potential errors in each of the measurements have been made, but the possibility of misleading data remains, particularly in the case of measurements taken from Cepheid variable stars. Cepheid variables are essential in determining the Hubble Constant as they serve as reference points for measuring the distances of galaxies millions of light-years away. However, these stars are often crowded together from our vantage point, making it challenging to separate and accurately measure their properties.
To tackle these limitations, astrophysicist Adam Riess and his team at the Space Telescope Science Institute (STScI) and Johns Hopkins University turned to the JWST, a powerful infrared telescope. They used the JWST to observe Cepheid variables in various galaxies, collecting observations of 320 of these stars.
Comparing the JWST observations with the noisy data from the Hubble Space Telescope, the researchers found that the two sets of observations were in agreement. This means that the Hubble data cannot be ruled out, and the Hubble tension remains unsolved.
While the mystery of the Hubble tension persists, scientists believe that one possible explanation could lie within the influence of dark energy. Dark energy is an elusive force that appears to have negative pressure and is thought to be responsible for the accelerated expansion of the Universe. The JWST measurements bring scientists one step closer to understanding this phenomenon.
“With Webb confirming the measurements from Hubble, the Webb measurements provide the strongest evidence yet that systematic errors in Hubble’s Cepheid photometry do not play a significant role in the present Hubble tension,” remarks Adam Riess.
The findings of this study have been accepted in The Astrophysical Journal and are available on arXiv. As researchers continue to grapple with the Hubble tension, the search for a more definitive answer regarding the expansion rate of the Universe continues.