Just like us, when we get older we leave the party behind and begin to lose energy, something very similar happens to the universe. And in the past the cosmos had a frenetic youth with an era known as ‘Cosmic Noon’10 billion years ago, where literally everything was a fireworks party with colliding galaxiesgas compressing and a great birth rate of our stars. But this party is coming to an end.
With this simile, we come to the conclusion that the Universe is entering a great decline, as has pointed out a gigantic study led by the Euclid Collaboration that points out that the Universe is not only cooling, but appears to have stuck at a “retirement temperature.”
How to do it. The question is mandatory, since understanding the health of the cosmos can be complex. That is why scientists choose to look at the ‘dust’ that exists throughout the galaxy and is the raw material for silicates and metals. with which the stars arise. The good thing is that this powder has a fundamental characteristic: it heats up.
In this way, when many new stars are forming in a galaxy, a very intense light is radiated that heats up the dust that surrounds it. That hot dust, in turn, emits a weak glow in the form of heat: far infrared light, which is precisely what we can measure from our planet.
Many tools. To make this measurement, a combination of observatories was used, such as Euclid, an ESA telescopewhich is creating the largest 3D map of the Universe and to do so provided an unprecedented census of 2.6 million galaxies. This information, together with old detections of far-infrared light, has been used to average the heat signal of thousands of galaxies of the same age and mass to obtain an incredibly precise average temperature reading.
What it tells us. In this way, there is a direct correlation that tells us that a galaxy with its hot dust is a ‘factory’ of stars at full capacity. But a galaxy with cold dust is something that is already in decline and stable.
The study confirms that in the “fever” of the Cosmic Noon, the galactic dust It reached average temperatures of 35 Kelvin (-238 °C). But as the Universe aged and star formation plummeted, that temperature began to drop. And this is where the key discovery comes.
The study indicates that the temperature does not continue to drop indefinitely. After a certain point (8 billion years ago), the temperature stops falling and stabilizes. Specifically, it has remained ‘stuck’ at -249.95 °C.
Because. What has basically happened is that the ‘thermostat of the Universe’ has changed from youth mode, where many stars were forming, to old age mode, where the dust warms up with the population of stars that exists, which is logically much colder.
This finding is crucial because it shows that the temperature of the dust, for the first time, has become independent of the mass of the galaxy. It doesn’t matter if it is a large or small galaxy; If it is in our time, its dust is around 23 Kelvins, or what is the same: -249.95 ºC.
Although 23 Kelvins is the new norm, it is just a pit stop on a much longer journey. This study is further proof that we live in a Universe in decline, dominated by dark energy that accelerates its expansion.
In this way, as space stretches, galaxies will become more isolated and their raw material will be depleted. That is why the future (although we will not see it) is that the old stars that maintain this stable temperature are going to die. It’s like those embers that emit constant heat to be able to cook in the fireplace, which go out little by little until it becomes completely cold.
The final destination, although billions of years away, remains the “Cold Death” of the cosmos: a state of maximum entropy where the temperature will reach Absolute Zero (-273.15 °C) and all activity will stop forever.
Images | Jeremy Thomas
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