Our universe is mainly composed of dark energy, which represents approximately 68 % of its total energy and matter content. Then there is the dark matter, which constitutes around 27 %, and, finally, the “normal” matter that we can observe, like stars and galaxies: only 5 %. It is obvious that dark energy, more than two thirds of the universe, has a lot to say about us.
Imagine that you see how a balloon is inflated, but instead of slowing down as it grows, it expands faster and faster. That is basically what scientists They discovered about our universe in 1998 through the explosion of stars called Supernovas.
They discovered that an unknown force, later called dark energy, was separating the space at an accelerated pace. Now, after analyzing more than 2000 of these stellar explosions, a team of scientists has discovered indications that Dark energy may not be as constant as we thought. In fact, it could be changing and possibly weakening over time.
The IA type supernovae are incredibly bright explosions that occur when a specific type of dead star, called white dwarf, accumulates too material and exploits. Are So brilliant that you can see billions of light years And, crucially, they all shine approximately with the same brightness.
This predictability of the brightness makes them the “standard candle”, perfect for measuring distances in space. Just as the distance to a lamppost can be estimated based on its brightness, astronomers can calculate the distance to the land of these supernovae. But here is the key: also measuring how much the light of these explosions has been stretched or displaced due to the expansion of spaceit is possible to determine the speed of expansion of the universe at different times of the past.
Since that discovery, winner of the Nobel Prize in 1998, astronomers have detected more than 2000 IA type Supernovas using different telescopes and techniques. But there was a problem: comparing data from all these sources was how to try to compare measurements taken with different metric systems. Each telescope and study had their own calibrations and differences.
To solve it, an international team, the Supernovas Cosmology project, dedicated years to create “UNION3”, The largest standardized supernova data set ever collected.
They thoroughly analyzed 2087 Supernovas of 24 different sets of data, adjusting all the differences between telescopes and polls to equate all the data. When the team, led by David Rubin, Analyzed this huge set of standardized data through statistical methods, they found something intriguing. The data suggests that dark energy may not have remained constant throughout history.
“Dark energy constitutes almost 70 % of the universe and is what drives expansion, so, If we are weakening, the expansion could be expected to be decelerated over time”, Says Rubin in a statement.
This possible change in dark energy has enormous implications for the final destination of our universe. Currently, Rubin works with a model called Lambda CDM, where dark energy (Lambda) It remains constant over time and counteracts gravitational attraction of matter (cold dark matter or CDM).
But if dark energy is weakening, the model could be very different. If the dark energy overcomes gravity, the universe continues to expand indefinitely, which could lead to a great explosion where space expands so fast that even atoms are torn. If gravity triumphs, the expansion could slow down, stop or even revert, becoming a great contraction where everything collapses. If they balance, on the other hand, the universe could reach a steady state.
What makes this discovery particularly exciting is that it does not come from a single source. An independent study, called spectroscopic instrument of dark energy (DESI), which studies how galaxies are grouped, It is detecting similar indications that dark energy could be evolving.