Scientists searching for dark matter in the universe have recorded one of the most uncommon phenomena in the universe: the decay of a Xenon-124 atom.
At the XENON1T dark matter detector within the Gran Sasso mountains in Italy, scientists announced the discovery that xenon-124, an isotope of the element Xenon, is unstable. Its half-life is reported to be 1.8 x 10 to the power 22 years that is roughly 1 trillion times longer than the current age of the universe.
XENON Observatory Records Rare Decay Of Xenon-124 Atom
The XENON1T is essentially a 1,300-kilogram of liquid xenon in a vat in a cryostat submerged nearly a mile underground. The instrument uses xenon because it is one of the most stable elements around; it does not react with pretty much anything, making it ideal to be used to detect one of the most elusive particles in the universe.
While it still has not successfully found dark matter, scientists of the XENON Collaboration, for the first time ever, spotted the decay of the xenon-124 atom.
"We actually saw this decay happen. It's the longest, slowest process that has ever been directly observed, and our dark matter detector was sensitive enough to measure it," stated Ethan Brown, an assistant professor of physics at Rensselaer Polytechnic Institute and is also one of the authors of the study published in the journal Nature.
"It's an amazing to have witnessed this process, and it says that our detector can measure the rarest thing ever recorded."
A half-life refers to the amount of time for half of the atom nuclei to spontaneously change through one of the many types of radioactive decay. In this case, the scientists observed a double-electron capture in which the two protons of the xenon atom absorbed two electrons simultaneously that resulted in two neutrons. Brown described the observation as "a rare thing multiplied by another rare thing, making it ultra-rare."
An Ultra-Rare Event
This is the first time that scientists have measured the half-life of xenon-124 based on the direct observation of its radioactive decay. The findings can also teach scientists about neutrinos, the second most abundant particles in the universe that are very difficult to detect and measure. The nature of neutrinos is not yet fully understood.
"The fact that we managed to observe this process directly demonstrates how powerful our detection method actually is — also for signals which are not from dark matter," stated Christian Weinheimer of the University of Münster and one of the authors of the study.
The next goal is to detect a neutrinoless double-electron capture.