Jan. 17 () –
A new measurement confirms that the universe is expanding faster than theoretical models and than can be explained with our current understanding of physics.
This discrepancy between the model and the data is known as the Hubble stress. Now, the results published in The Astrophysical Journal Letters they provide even stronger support for the faster rate of expansion.
“The tension now becomes a crisis,” said Dan Scolnic, a theoretical physicist at Duke University who led the research team.
Determining the expansion rate of the universe, known as the Hubble constant, has been a major scientific quest since 1929. when Edwin Hubble first discovered that the universe was expanding.
Professor Scolnic explains it as an attempt to construct the growth table of the universe: we know what size it was at the Big Bang, but how did it get to the size it is now? In your analogy, the image of the universe as a baby represents the distant universe, the primordial seeds of galaxies.
The current universe image represents the local universe, which contains the Milky Way and its neighbors. The standard model of cosmology is the growth curve that connects the two. The problem is that things don’t connect.
“This means, to some extent, that our model of cosmology could be broken,” Scolnic said. in a statement.
Measuring the universe requires a cosmic ladder, which is a succession of methods used to measure distances to celestial objects, with each method, or “rung,” building on the previous one for calibration.
The ladder used by Scolnic was created by an independent team using data from the Dark Energy Spectroscopic Instrument (DESI), which observes more than 100,000 galaxies each night from its observation point at the Kitt Peak National Observatory.
Scolnic recognized that this ladder could be anchored closer to Earth with a more precise distance to the Coma cluster, one of the closest galaxy clusters to us.
“The DESI collaboration did the really difficult part, their ladder was missing the first rung,” Scolnic said. “I knew how to get it, and I knew that would give us one of the most precise measurements of the Hubble constant that we could get, so when his paper came out, “I left absolutely everything and worked on this non-stop.”
To obtain an accurate distance to the Coma cluster, Scolnic and his collaborators used the light curves of 12 type Ia supernovae within the cluster. Like candles illuminating a dark path, type Ia supernovae have a predictable luminosity that correlates with their distance, which makes them reliable objects for distance calculations.
The team reached a distance of about 320 million light years, almost in the center of the range of distances reported over 40 years of previous studies, a reassuring sign of their accuracy.
“This measurement is not biased by how we think the Hubble tension story will end,” Scolnic said. “This cluster is in our backyard, it has been measured long before anyone knew how important it was going to be.”
Using this high-precision measurement as a first step, the team calibrated the rest of the cosmic distance scale. They arrived at a value for the Hubble constant of 76.5 kilometers per second per megaparsec, which essentially means that the local universe is expanding 76.5 kilometers per second faster every 3.26 million light years.
This value matches existing measurements of the expansion rate of the local universe. However, like all such measurements, it conflicts with measurements of the Hubble constant using predictions from the distant universe.
In other words: it matches the expansion rate of the universe as other teams have recently measured it, but not as our current understanding of physics predicts. The old question is: Is the fault in the measurements or in the models?
The Scolnic team’s new results provide strong support for the emerging idea that the root of the Hubble strain lies in the models.
“Over the last decade or so, there have been a lot of reanalyses by the community to see if my team’s original results were correct,” said Scolnic, whose research has consistently challenged the Hubble constant predicted using the Standard Model of physics.
“Ultimately, even though we’re exchanging so many pieces, we all get a very similar number. So, to me, this is the best confirmation I’ve ever received.”
“We’re at a point where we’re pushing very hard against the models we’ve been using for two and a half decades, and we’re seeing that things don’t match up,” Scolnic said.
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