We have the most accurate measurement to date of what makes up the Universe

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Physicists have spent years wondering why and how the Universe is expanding. The most widespread theory implies the existence of a combination of matter and energy that we cannot perceive or study. Now, a team of researchers under the Pantheon+ collaboration has managed to estimate how many of these our Universe can hold.


A question not so easy to answer.
doWhat is the universe made of? It might seem like an easy question to answer. After all, we know all the elements of the periodic table that can appear naturally, and even some more.

However, there is something else in the Universe besides this matter that we can see and perceive: dark energy and dark matter. These concepts refer to matter and energy that we cannot detect (that is, not only can we not see it, we have no way of finding it) but that leave their mark on the structure of the Universe.

Specifically, dark matter would leave its mark through the gravitational force. Dark energy for its part would leave its mark on the speed at which the Universe is expanding.

The new mystery of dark matter is its absence: they detect a galaxy that seems to be free of it and scientists do not explain it

Two thirds energy, one third matter.
The latest, and to date most accurate estimate of the ratio in which we can find dark energy, dark matter, and conventional matter has recently been published in an article in the magazine The Astrophysical Journal.

In it, the research team explains that dark energy makes up 66.2% of our cosmos, while 33.8% corresponds to matter. Of the total, conventional matter would make up only 5% according to this recent estimate.

Matter and speed.
But that is not the only result that has been presented in the article. The collaboration between the Pantheon+ project and the SH0ES collaboration has made a new estimate of the hubble constantthe constant that tells us the rate at which the universe is expanding.

The new estimated value is 73.4 kilometers per second per megaparsec, or abbreviated (km/s)/Mpc, a measurement that has been given a margin of error of 1.3%. This means that, due to the expansion of the Universe, a galaxy that is one megaparsec from us (3.2 million light years) will be moving away from us at 73.4 km/s. And all this without moving, since the expansion of the Universe does not imply the movement of the objects in it, but the stretching of space itself.

According to the team’s calculations, the rate at which the Universe as a whole is expanding probes the 255,000 kilometers per hour.

More fuel to the fire of the great cosmological discrepancy.
This is troublesome. In recent years, a major discrepancy in the measurement of the Hubble constant has become increasingly noticeable. Cosmological models created from the information extracted from the microwave background estimate that the Hubble constant should be around 67 (km/s)/Mpc.

In this period, the measurements have become more precise and the margins of error smaller, but while the measurements based on the observation of galaxies, supernovae and other objects give us figures around these 73.4 (km/s)/ Mpc, measurements based on the microwave background remain significantly below.

It’s the discrepancy known as the Hubble strain, and it’s already reached the five sigma level, meaning it’s extremely unlikely to be due to chance.

Observe supernovae.
To achieve the results, the researchers analyzed around 1,500 type Ia supernovae. Supernovae are explosions that occur at the end of the life of some stars, once they become white dwarfs, if they accumulate a large amount of matter, they can develop a thermonuclear reaction and explode in one of these supernovae.

The team has accumulated decades of observations, explains one of its authors, the Nobel laureate in physics Adam Ries, in a press release. “In many ways, this latest Panteon+ analysis is the culmination of more than two decades of diligent efforts by observers and theorists around the world to unravel the essence of the cosmos.”

One step on a long road.
Pantheon+ is the continuation of the Pantheon project, to which the researchers owe observations of the first thousand supernovae. But without a doubt the most interesting thing is what lies ahead, not for this particular project but for the scientific community.

In words collected by France 24Study co-author Dillon Brout explained this maxim: “We as scientists thrive on not understanding everything.” Three of the biggest mysteries in astrophysics are here, and who knows when or if we’ll be able to solve them.

Image | NASA/CXC/U.Texas

Physicists have spent years wondering why and how the Universe is expanding. The most widespread theory implies the existence of…

Physicists have spent years wondering why and how the Universe is expanding. The most widespread theory implies the existence of…

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