Once again, the universe reminds us how much we have to understand about its deepest mysteries. In a new turn that is shaking the foundations of modern cosmology, recent measurements not only confirm previous controversial results on the rapid expansion of the cosmos, but deepen the enigma: the universe expands faster than our theoretical models can explain. The discrepancy is so significant that experts have stopped referring to it as a mere “tension” and now they openly speak of a “hubble crisis”, pointing out a possible turning point in our understanding of the cosmos.
The dilemma dates back to 1929, when Edwin Hubble discovered that the universe constantly expands. Since then, scientists have tried to determine the speed of this expansion, known as the Hubble constant, using two different methods.
Measuring expansion: two divergent paths
On the one hand, direct measurements use “standard candles”: objects with known luminosity, such as Ia type supernovae or cefid variables. Measuring its apparent brightness, its distance is determined and compared to the speed at which they move away, deduced from their red shift. According to Space.com, These observations suggest that the Hubble constant is around 73 kilometers per second by Megapársec (73 km/s/mpc).
The second method looks towards the most remote past in the universe, studying the oldest light that we can detect: the cosmic microwave background (CMB), emitted when the universe was only 379,000 years old. The Planck satellite of the European Space Agency analyzed this original radiation and, applying the standard model of cosmology (dominated by cold dark matter and dark energy, which operates under the province of the general theory of the relativity of Albert Einstein), predicted a value of 67.4 km/s/mpc. Both measurements are very precise, but incompatible with each other, and from that disparity the so -called “hubble tension” is born.
A new discovery sharpens the crisis
Now, a new discovery has stirred even more the waters of this cosmological debate. A team led by Dan Scolnic, from Duke University, and Adam Ries, from Johns Hopkins University, has found evidence that deepens the crisis in our own cosmic “neighborhood”.
According to his study, published in The Astrophysical Journal Letters, The coma galaxies cluster – one of the groups of galaxies closest to Earth – is significantly closer than it should be: Space.com It reports that it is 321 million years-years away, while the standard model predicts that it should be 359 million years-years. This 38 million-year-old discrepancy is not a simple measurement error, but a new indication that something fundamental could be failing our understanding of the cosmos.
“I like to think about Hubble’s tension like when you were a child in the doctor’s office,” explains Scolnic in statements collected by Space.com. “The doctor could say, well, if you are like that when you are young, you will be that big when you are an adult … in astronomy we can do the same with images of the cosmic microwave background, which is when the universe was a baby, To predict the big and fast that the universe would be expanding today.
The results of the Scolnic team are especially significant because coma cluster has been studied for decades, long before the Hubble tension debate existed. As the researcher points out in a statement from the University of Duke, “This cluster is in our backyard, it has been measured long before anyone else knew how important it was.”
The cosmic ladder: precise measurements
For Scolnic, this new measurement serves as the first step of a “cosmic ladder” that calibrates all other distances. Not only does it coincide with previous studies that also placed coma for about 320 million light years, but intensifies the discrepancy between the observed reality and the prediction of the cosmological model. In other words, as the University of Duke points out, the measurement coincides with the expansion rate of the universe as other teams have recently measured, but not as predicts by our current understanding of physics. “The tension now becomes a crisis,” says Scolnic himself.
To reach this conclusion, the researchers used an innovative “cosmic ladder” based on data from the spectroscopic instrument of dark energy (DESI). As a fundamental step of their measurement, they studied 12 IA type supernovae in the coma cluster. These star explosions act as perfect “standard candles”: their brightness is so predictable that they allow calculating cosmic distances with great precision. Using this new calibration, the team calculated that the Hubble constant is 76.5 kilometers per second by Megaparsec, which means that each segment of the 3.26 million-year-old universe expands 76.5 kilometers every second, a significantly higher speed than the predicted by the standard model.
From its location at the National Kitt Peak Observatory, Desi currently observes more than 100,000 galaxies. “The collaboration DESI made the part really difficult,” said Scolnic, although he added that “the first step was missing.”
In the past there are those who have pointed to bury this tension. In the summer of 2024, a team led by Wendy Freedman (University of Chicago) measured the distance to ten galaxies using the James Webb space telescope and obtained a value that coincided with the standard model. But, as Scolnic points out, based only on ten galaxies is risky, and the new coma results return the enigma to the front line.
“We should not rush to discard what has served us so well so far,” says Scolnic, recognizing that coma cluster data leaves little space to deny the existence of Hubble tension.
What does all this mean?
In that sense, scientists face two possibilities: o There is some error in our measurements (something less and less likely since different teams obtain similar results), or our universe model needs a serious review.
Some tentative explanations suggest that there could have been an additional explosion of dark energy in the primitive universe, or that exotic particles called axions could have injected extra energy into the early cosmos. But as he points out Space.comeverything is still speculative.
What is clear is that this discrepancy can no longer be ignored. As a scolnic sentence: “We are pressing very strong against the models we have been using for two and a half decades, and we are seeing that things do not coincide. This may be changing our way of thinking about the universe, and it is exciting! Cosmology surprises and who knows what discoveries will come later. “
Edited by Felipe Espinosa Wang with information from Space.com, Duke University and Cosmos.
