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Expansion rate of the universe confirmed by JWST

One of the fundamental parameters for understanding the evolution and ultimate fate of the cosmos is the rate at which the universe is expanding. This is known as the Hubble constant, and it has now been confirmed thanks to the unprecedented capabilities of NASA’s James Webb Space Telescope (JWST).

Understanding the Hubble constant and its tension

The rate at which the universe expands is termed the Hubble constant. Its precise measurement provides insights into the universe’s evolution and its ultimate fate.

However, a difference, known as the “Hubble Tension”, has persisted. This difference arises between the Hubble constant’s measured value using various distance indicators and the value predicted from the afterglow of the big bang.

JWST’s role in refining the measurements

Nobel Laureate Adam Riess, affiliated with the Johns Hopkins University and the Space Telescope Science Institute, recently highlighted the significant contribution of the JWST in enhancing the precision of local measurements of the Hubble constant.

For astronomers, deciphering the universe’s expansion rate is akin to squinting to see a sign on the horizon. The sign, in this case, is the brightness of distant galaxies’ stars, which can reveal the universe’s expansion rate.

Particularly, Cepheid variables, a type of supergiant star with brightness levels a hundred thousand times that of the Sun, have been a gold standard for measuring distances in the universe. Their unique pulsating nature allows for accurate distance measurements to galaxies hundreds of millions of light years away. However, one significant challenge arises due to the close proximity of stars in galaxies when viewed from Earth. This makes it difficult to differentiate one star from another.

The Hubble Space Telescope and its limitations

The Hubble Space Telescope, launched in 1990, was developed partly to address this differentiation problem. It offered enhanced visible-wavelength resolution, allowing it to identify individual Cepheid variables in distant galaxies and determine the interval they took to change their brightness.

However, the Hubble had limitations in observing the Cepheids in near-infrared, which is crucial to bypass the effects of intervening dust on light. This introduced noise into the measurements.

Webb’s infrared superpowers

The JWST, with its powerful infrared vision, steps in here. Its advanced optics enable it to separate Cepheid light from nearby stars with minimal blending. In their study, Riess and his team utilized the JWST to observe over 320 Cepheids and found that previous measurements made by Hubble were indeed accurate, though with more noise. The data from the JWST corroborated Hubble’s, solidifying the confidence in those measurements.

The underlying question, however, remains unresolved: why is the universe expanding so quickly? Predictions from the cosmic microwave background suggest a certain rate of expansion, but current measurements surpass this prediction, leading to the Hubble Tension.

Some theorize that this discrepancy may point to previously unknown cosmic phenomena, such as strange forms of dark energy or dark matter, a potential revision in our understanding of gravity, or even a new kind of particle or field.

Webb’s contribution and the road ahead

With the JWST affirming Hubble’s readings, the possibility of systematic errors in Hubble’s measurements being the cause of the Hubble Tension diminishes. This places more profound explanations firmly on the table. As the mystery deepens, scientists eagerly anticipate further revelations from the JWST and other advanced instruments, hoping to unravel this cosmic conundrum.

In its journey, the James Webb Space Telescope, an ambitious collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency, promises to unlock many more secrets of our universe, reaffirming our quest to understand our place within it.

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