Searching for Undiscovered Particles Around Black HolesCategory: Science & Technology
Posted: June 22, 2012 11:03AM
Discovering new particles can be very difficult because of their small size and smaller lifespan. Take neutrinos for example; these particles are so small they will whiz through matter without ever interacting with it but also have such a short lifespan that if it were not for relativity, we would be unable to detect those made by the Sun. In our massive accelerators it is even more difficult though as we sometimes do not find a particle by detecting it but by detecting what it decays into. Now researchers at the Vienna University of Technology are looking to find one kind of particle hanging around black holes using gravitational waves.
Called axions, these proposed particles have extremely low mass and have yet to be detected. What the researchers have proposed is that we can use their low mass, which translates to low energy as well, to find them around black holes. Those massive structures have so much energy in and around them that some of it can easily transform into axions. These particles would then be orbiting the black hole in a similar way to how electrons orbit a nucleus, but with on major difference. Electrons are fermions while axions should be bosons.
A property of all fermions is that they obey the Pauli Exclusion Principle which forbids two fermions to have the same quantum state at the same time. This is why electron orbitals have certain capacities. Bosons, which include photons, do not obey this principle and can coexist in the same place. This means it would be possible for a cloud of axions to form and orbit a black hole. This cloud may not be stable though and eventually it will collapse. This sudden event would vibrate spacetime in such a way as to make gravitational waves that we can detect.
According to General Relativity, spacetime can be distorted by gravity. You can think of it as a sheet partially stretched out. If you drag your finger along the sheet, you cause it to stretch out more where your finger is and the wrinkles that stretching causes are gravitational waves. Researchers have built massive facilities to detect these distortions, but they are not accurate enough to discern a gravitational wave from a normal vibration. Hopefully that accuracy can be achieved by 2016, but until then, the knowledge of axions and particles like it will have to wait.