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NASA’s Webb and Hubble Telescopes Confirm Universe’s Expansion Rate, Puzzle Persists


Newswise — When you’re trying to solve one of cosmology’s greatest puzzles, you need to triple check your homework. The puzzle, called the “Hubble tension,” is that the current rate of expansion of the universe is faster than astronomers expect, based on the initial conditions of the universe and our understanding current evolution of the universe.

Scientists using NASA’s Hubble Space Telescope and many other telescopes consistently find a number that does not match predictions based on ESA (European Space Agency) observations. Planck assignment. Does resolving this gap require new physics? Or is this the result of measurement errors between the two different methods used to determine the rate of expansion of space?

Hubble has been measuring the current rate of expansion of the universe since 30 years, and astronomers want to eliminate any lingering doubts about its accuracy. Now, Hubble and NASA’s James Webb Space Telescope have teamed up to produce definitive measurements, reinforcing the hypothesis that something else – not measurement errors – is influencing the expansion rate.

“Once measurement errors are canceled out, what remains is the real and exciting possibility that we have misunderstood the universe,” said Adam Riess, a physicist at Johns Hopkins University in Baltimore. Riess is the recipient of a Nobel Prize for co-discovering that the expansion of the universe is accelerating, due to a mysterious phenomenon now called “dark energy.”

As a cross-check, a first sighting of Webb in 2023 confirmed that Hubble’s measurements of the expanding universe were accurate. However, in hopes of easing Hubble’s strain, some scientists have hypothesized that invisible errors in measurements might increase and become visible as we delve deeper into the universe. In particular, stellar crowding could systematically affect brightness measurements of more distant stars.

The SH0ES (Supernova H0 for Dark Energy Equation of State) team, led by Riess, obtained additional observations with Webb of objects that are critical cosmic markers, known as Cepheid variable starswhich can now be correlated with Hubble data.

“We have now covered the full range of what Hubble observed, and we can rule out measurement error as a cause of Hubble’s strain with very high confidence,” Riess said.

The team’s first Webb observations in 2023 managed to show that Hubble was on the right track by firmly establishing the fidelity of the first rungs of the so-called cosmic distance scale.

Astronomers use various methods to measure relative distances in the universe, depending on the object being observed. Collectively, these techniques are known as the cosmic distance ladder – each step or measurement technique builds on the previous step for calibration.

But some astronomers have suggested that as it moves outward along the “second rung,” the cosmic distance scale could become fragile if Cepheid measurements become less precise with distance. Such inaccuracies could occur because light from a Cepheid could mix with that of an adjacent star – an effect that could become more pronounced with distance as stars cluster together and become harder to distinguish from one another. others.

The observational challenge is that past Hubble images of these more distant Cepheid variables appear more clustered and overlap with neighboring stars at increasingly greater distances between us and their host galaxies, requiring consideration careful account of this effect. The presence of dust further complicates the certainty of visible light measurements. Webb cuts through the dust and naturally isolates Cepheids from nearby stars because its vision is sharper than Hubble’s in infrared wavelengths.

“The combination of Webb and Hubble gives us the best of both worlds. We find that Hubble’s measurements remain reliable as we move further up the scale of cosmic distances,” Riess said.

Webb’s new observations include five galaxies hosting eight Type Ia supernovae containing a total of 1,000 Cepheids, and extend to the most distant galaxy where Cepheids have been well measured – NGC 5468 – at a distance of 130 million light years away. “This covers the entire range in which we have made measurements with Hubble. So we have reached the end of the second rung of the cosmic distance ladder,” said co-author Gagandeep Anand of the Space Telescope Science Institute in Baltimore, which operates the Webb and Hubble telescopes for NASA.

Further confirmation by Hubble and Webb of the Hubble voltage sets up other observatories to possibly solve the mystery. NASA’s next Nancy Grace Roman Space Telescope will conduct extensive celestial surveys to study the influence of dark energy, the mysterious energy that accelerates the expansion of the universe. the ESA Euclid The observatory, with the contribution of NASA, is pursuing a similar task.

At present, it is as if the distance scale observed by Hubble and Webb had firmly fixed an anchor point on one of the banks of a river, and the afterglow of the big bang observed by the Planck’s measurements since the beginning of the universe were firmly fixed on the other side. . How the expansion of the universe evolved over the billions of years between these two endpoints has not yet been directly observed. “We need to find out if we are missing something about how to connect the beginning of the universe and our days,” Riess said.

These results were published in the February 6, 2024 issue of Letters from the astrophysical journal.

The Hubble Space Telescope has been operating for more than three decades and continues to make groundbreaking discoveries that shape our fundamental understanding of the universe. Hubble is an international cooperation project between NASA and ESA. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. Goddard also conducts mission operations with Lockheed Martin Space in Denver, Colorado. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble and Webb science operations for NASA.

The James Webb Space Telescope is the world’s first space science observatory. Webb solves the mysteries of our solar system, looks beyond distant worlds around other stars, and probes the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

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Media Contact:
Ray Villard/Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland
(email protected) / (email protected)


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