Our knowledge of the universe changed decisively in December 1997. That month, the Hubble Space Telescope detected a tremendous flash that occurred more than 10 billion years ago. It was the supernova explosion baptized as 1997ff, which occurred in a very distant elliptical galaxy. In fact, it was the most distant phenomenon of this kind ever observed.
Then, two groups of astronomers came into action: the Supernova Cosmology Project , led by Saul Perlmutter, of the Lawrence Berkeley National Laboratory, in the USA; and the High-Z Supernova Search Team , led by Brian Schmidt of the Australian National University.
Something no one expected to find
Both teams of researchers were dedicated to determining the distance at which the most distant galaxies are, for which they were tracking a peculiar type of supernovae called Ia.
What makes them so interesting is that they all shine exactly the same, so if you measure their brightness it is possible to know how far away they are. The data also serves to know the value of one of the most important numbers in cosmology, the deceleration parameter, which accounts for the change in the expansion speed of the cosmos.
Well, what they found took them completely by surprise. All of the Ia supernovae they encountered appeared 20% weaker than expected. That just didn’t make sense. Making good the Sherlock Holmes adage “once the impossible is discarded, what remains, improbable as it may seem, is true,” scientists came to the same conclusion: the universe had expanded 10% faster in the last few thousand years. millions of years.
That meant there must be something that exerted some kind of repulsion and was pulling galaxies away faster than anticipated: dark energy.
