Based on decades of Hubble observations, researchers have found that the universe is expanding faster than expected. It remains to be seen what new secrets lie behind this new measure.
Hubble is slowly giving up its place as NASA’s darling to the gleaming James Webb Space Telescope, but that doesn’t mean it’s obsolete, quite the opposite. Recently, researchers have even used the data he has collected over 32 years to refine measurements of a fundamental element of astrophysics: the expansion rate of the universe.
In fact, all currently valid astrophysical models indicate that our universe has continued to swell since its “birth” that dates back to the famous Big Bang. An observation that does not change much in the everyday life of earthlings, but has an enormous influence on the daily work of researchers.
It is particularly important to know the speed of this expansion – a value also known as… the Hubble constant, named after the famous astronomer who discovered the phenomenon. Because of this expansion, it is possible, for example, that the actual distance between two very distant objects is much greater than that calculated from few known physical parameters.
A long-standing conundrum for astrophysicists
This is just an isolated example; Importantly, the speed of 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 to the present day to test our understanding of the universe from end to end“, She explains.
The problem is that the exact speed of this expansion is still a matter of much debate. For reasons that are still unclear, different observatories that have attempted to calculate it by staring at a patch of sky have regularly yielded vastly different results.
Differences that have long puzzled researchers. Is it an instrument accuracy issue? A methodological error? A fundamental misunderstanding of the problem? Fortunately, thanks to the work of teams at NASA and the University of Baltimore, the answer to these questions is fast approaching.
To calculate this value, they spent several decades researching spatial “beacons” and then cataloging them to refine existing results. In this case, they chose to base themselves on the 42 supernovae discovered by Hubble since it went online.
Very often, supernovae are extremely violent explosions that occur towards the end of the life of certain stars. They radiate such energy that the signals associated with them are relatively easy to detect and remain so for a long time, at least on a human scale. So these supernovae are real beacons that help astronomers find their way in the vastness of the cosmos.
“Something strange is happening“
By analyzing their relative positions over the years, researchers have been able to precisely measure the expansion rate of the universe. Through the eminent Adam Riess, 2011 Nobel laureate, they have just “the most accurate measurement of the universe’s expansion rate from the ultimate telescopes and space markers“.
According to them, the “constant” (it’s not technically not a constant) from Hubble would be worth 73km/s/MPC, which means 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 the 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 allows an error to be described as extremely unlikely – less than a million chances.
Not particularly sexy works from a mainstream perspective, but they could well become the latest understated masterpiece from this aging telescope. “That’s what it was built for‘ explains Riess. “It’s probably Hubble’s magnum opus.‘ he then concedes. “It required an enormous amount of extremely detailed work‘ adds Licia Verde.
And these superlatives are well deserved. Because since the expansion phenomenon was first identified, new concepts have emerged. We can cite the famous dark energy, the exact nature of which remains unknown, but which seems to play a crucial role in the expansion. And this is where this measure becomes very interesting. Because this new measuresupports the idea that something strange is going on, probably related to brand new physics concepts“, explains NASA in its press release.
Ultimately, the exact number doesn’t really interest the researchers as such. If they’ve been chasing it for so long, that’s mainly because it’s likely a much-needed key to unlocking some of the universe’s darkest mysteries. “In fact, I don’t care what the specific value of the expansion ratio is.‘ Riess admits. “On the other hand, I really like using it to learn things about the universe!“, he specifies. So all you have to do is wait!
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