We don’t know what substance is. We do know what it isn’t, and that’s a drag. Matter is formed of elementary particles, from the quarks and electrons that structure atoms and molecules, to primordial neutrinos spread throughout the cosmos. But none of the known elementary particles can comprise substance, so what’s it?
Several ideas are proposed, from Weakly Interacting Massive Particles (WIMPs), to hypothetical particles referred to as axions, to tiny black holes. But thus far, the evidence doesn’t really support these ideas. So astronomers have looked to a different theoretical particle referred to as sterile neutrinos.
Neutrinos are a sort of substance, because they need mass, and weakly interact with light. But neutrinos have such a little mass and high energy that they move through the universe at nearly the speed of sunshine. For this reason, they’re referred to as hot substance. we all know from observations that substance is usually cold, meaning that substance particles must move relatively slowly. So while neutrinos structure a little a part of substance, most of it must be something else.
Neutrinos possess three known types or flavours, and that they have some rather strange properties. one among these strange properties is their helicity. Elementary particles have spin, and once they travel the spin is either oriented along their direction of motion (right-handed helicity) or opposite to their motion (left-handed helicity). Most particles can have either helicity counting on the interaction, but the helicity of neutrinos is usually left-handed. We are unaware of the reason, but we do know that if right-handed neutrinos exist they wouldn’t interact with regular matter through the electroweak force. they might only interact with matter gravitationally, in order that they are referred to as sterile neutrinos.
If sterile neutrinos exist, and that they are just regular neutrinos with right-handed helicity, then they might be hot substance and not the cold substance we’re trying to find. But there are some theories where sterile neutrinos are far more massive than regular neutrinos. These heavy sterile neutrinos could comprise substance. that’s if they exist.
If there are heavy sterile neutrinos out there, they might be discovered by their decay. Heavy particles can decay into lighter particles over time, so it’s possible that sterile neutrinos can decay to their lighter counterparts, emitting x-ray photons within the process. In an attempt to get these x-ray emissions, a team searched data from the Chandra X-Ray Observatory. They didn’t find any evidence of sterile neutrinos. Their results weren’t strong enough to thoroughly rule out the thought, but it does narrow down the theoretical candidates a touch. Specifically, the study places a tough limit on how sterile neutrinos can decay if they exist. We still don’t know what substance is. Studies like this might sound disappointing, but they play a crucial role. By narrowing down our options, they force us to specialise in more viable substance candidates. We’ve learned something more, except for now, we are still within the dark.