Thanks to Hubble, NASA is advancing on the mystery of the expansion of the universe

Based on decades of Hubble observations, researchers have determined that the universe is expanding faster than expected. It remains to be seen what new mysteries hide under this new measure.

Hubble is slowly ceding its place as NASA’s darling to the gleaming James Webb Space Telescope, but that doesn’t mean it’s become obsolete, far from it. Recently, researchers have even used the data he has captured over 32 years to refine measurements of a fundamental element of astrophysics: the rate of expansion of the universe.

Indeed, all the astrophysical models currently in force suggest that our universe has continued to swell since its “birth”, which dates back to the famous Big Bang. An observation that does not change much in the daily life of earthlings, but which has a huge impact on the daily work of researchers.

It is particularly important to know the speed of this expansion – a value called… Hubble constant, named after the illustrious astronomer who discovered the phenomenon. For example, because of this expansion, it is possible that the actual distance between two very distant objects is much greater than that calculated from a few known physical parameters.

A long-standing puzzle for astrophysicists

This is just an isolated example; what is important is that the speed of the expansion of the universe is a crucial datum on which very important works are based. “The Hubble constant is a very special number”, explains Licia Verde, cosmologist at the University of Barcelona. “We can use it to pull the thread of our past until today to test our understanding of the universe from end to end”, she explains.

The problem is that the precise speed of this expansion is still highly debated. For reasons still unclear, different observatories that have attempted to calculate it by staring at a patch of sky have regularly produced significantly different results.

Differences that have long puzzled researchers. Is it an instrument accuracy issue? A methodological error? A fundamental misunderstanding of the problem? Fortunately, the answer to these questions is getting closer thanks to the work of teams from NASA and the University of Baltimore.

To calculate this value, they spent several decades researching and then cataloging spatial “beacons” to refine existing results. In this case, they chose to base themselves on the 42 supernovae spotted by Hubble since its commissioning.

Very commonly, supernovae are extremely violent explosions that occur towards the end of the life of certain stars. They emit such energy that the associated signals are relatively easy to detect and remain so for a long time, at least on a human scale. These supernovae are therefore real beacons that help astronomers find their way around the vastness of the cosmos.


Something strange is happening

It is by analyzing their relative positions over the years that researchers have been able to measure the expansion rate of the universe with precision. Through the eminent Adam Riess, Nobel Prize winner in 2011, they have just presented “the most accurate measurement of the expansion rate of the universe from the ultimate in telescopes and space markers”.

According to them, the “constant” (it is not technically not a constant) from Hubble would be worth 73 km / s / Mpc, which means that the size of the universe will double within 10 billion years. It’s a number significantly higher than 67.15 km/s/Mpc measured by ESA which served as a reference until then. And for the first time in this context, this measurement falls within the framework of the famous “five sigma”. This is a statistical safety threshold that makes it possible to state that an error is extremely improbable – less than a chance in a million.

Not particularly sexy works from a mainstream perspective, but they could well become the latest understated masterpiece from this aging telescope. “This is what it was built for”, explains Riess. “It’s probably Hubble’s magnum opus.“, he concedes then. “It required a tremendous amount of extremely detailed work”, adds Licia Verde.

And these superlatives are well deserved. Because since the phenomenon of expansion was first identified, new concepts have appeared. We can cite the famous dark energy, whose exact nature remains unknown, but which seems to play a decisive role in the expansion. And this is where this measure becomes very interesting. Because this new measure “supports the idea that something strange is going on, probably related to brand new physics concepts“, explains NASA in its communiqué.

Ultimately, the precise figure does not really interest researchers as such. If they’ve been chasing it for so long, it’s mostly because it’s probably a much-needed key to unlocking some of the darkest mysteries in the universe. “In fact, I don’t really care what the specific value of the expansion rate is.”, concedes Riess. “On the other hand, I really like to use it to learn things about the universe!”, he specifies. So all you have to do is wait!

Source: Journal du Geek by

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