James Webb Space Telescope confirms universe’s expansion rate and one of physics’ biggest mysteries

timeThe James Webb Space Telescope has confirmed the results of smaller telescopes about the rate of expansion of the universe. Instead of resolving the physics debate, this made things worse, because previous measurements contradicted what astronomers thought should be happening. echo of the big bang.This (probably) doesn’t mean we need to throw out much of what we think we know about cosmology, as some people know Popular articles claimbut it does leave a major problem to solve.

Astronomers have proposed a variety of methods to determine how fast the universe is expanding, a measurement that has important implications for the age and future of the universe. Initially, these all come with a lot of uncertainty, and while the core forecasts are different, the error bars overlap, so there’s not much to worry about.

However, as our instruments continue to improve and the number of research sources increases, the differences do not disappear. This is now known as the Hubble tension, in reference to the Hubble constant, a number that defines the relationship between distance and velocity of distant objects.

JWST is able to perform one of the key measurements, the distance to distant galaxies, with greater precision than any other instrument. Some astronomers think it might provide an answer to the Hubble tension that is closer to that obtained by other means. Instead, it supports results from other telescopes.

“Have you ever had trouble seeing a sign at the edge of your field of vision? What does it say? What does it mean? Even with the most powerful telescopes, the ‘sign’ that astronomers want to read appears so small that As for us, too, Adam Riess, a professor at Johns Hopkins University who shared the 2011 Nobel Prize in Physics for proving that the expansion of the universe is accelerating, said in a statement.

“The signature that cosmologists want to decipher is the cosmic speed limit signature, which tells us how fast the universe is expanding, a number called the Hubble constant. Our signature is written into stars in distant galaxies,” Reese explained. . The brightness of some of the stars in these galaxies tells us how far away they are from us, and therefore how long it takes for this light to reach us, while the redshift of the galaxy tells us how much the universe has expanded during that time, thus telling We swell.”

Reese was awarded the prize for helping make this measurement using Type Ia supernovae, which have very consistent intrinsic brightness at their peak. However, this would require waiting for the right type of supernova explosion. Stars called Cepheid variables offer an alternative that is far more abundant.

The brightness of Cepheids is related to the rate at which they expand and contract, which again gives us measurements that can be used to calculate their distances. Cepheids have given us a first glimpse into the scale of the universe, revealing that distant galaxies lie beyond the Milky Way.

However, Cepheids are not as bright as supernovae and are not visible in the most distant galaxies. However, hundreds of millions of light-years away, they can calibrate supernova measurements, providing additional precision, but only if we can distinguish them from ordinary nearby stars.

JWST, which operates at wavelengths more accessible than the Hubble range, used it to measure more than 320 Cepheid variables, some of which are located in the relatively nearby galaxies NGC 4258 and NGC 5584, which host recent supernovae.

Their measurements show that lack of confidence in Hubble’s accuracy is unfounded because it measures these galaxies so well. However, the findings from the two space telescopes are completely inconsistent with predictions based on the cosmic microwave background.

The Harper tension remains unresolved.

The most exciting possibility, Reese adds, is that tension is some of the missing clues in our understanding of the universe. “It could reveal the existence of exotic dark energy, exotic dark matter, a revision of our understanding of gravity, or the presence of unique particles or fields. As if ordinary dark energy and dark matter weren’t puzzling enough.

Four centuries later, Shakespeare was still right: yes There are more things in heaven and on earth than any human philosophy could have dreamed of, including that of Horatius.

The research has been accepted by The Astrophysical Journal and a preprint is available on ArXiv.org.

An earlier version of this article was published in September 2023