Have you ever ever seemed up on the night time sky and puzzled what you are not seeing? The skies could also be filled with invisible “boson stars” which might be product of an unique type of matter that doesn’t shine.
We strongly suspect that the universe is filled with darkish matter, which makes up round 25% of all of the mass and vitality within the cosmos. However whereas circumstantial proof abounds and we consider that darkish matter is a few type of undiscovered particle, we have no direct proof of such a particle.
For a few many years, we thought we have been heading in the right direction with a brand new sort of particle referred to as a weakly interacting huge particle (WIMP). Predicted from varied supersymmetry theories, the WIMP would have a mass someplace within the vary of the heavier recognized particles, like the highest quark. However in any other case, it could be largely invisible, interacting with regular matter solely often.
However searches for WIMPs have failed to seek out something. That is effective; nature isn’t obliged to go together with our first guess. Fortunately, we’ve one other particle candidate ready within the wings: the axion.
The axion was launched to resolve a nasty downside involving the sturdy nuclear power. By all observations, the sturdy power obeys two vital symmetries in nature: cost and parity. Which means for those who take a powerful power interplay, flip the costs of all of the particles to their reverse values, and have a look at the response within the mirror, you will get the identical consequence.
However nothing within the principle itself says that it ought to obey these symmetries. Physicists tried to repair this by basically including a brand new parameter to the equations and setting that parameter to zero, however that felt a bit pressured. Then got here an ingenious resolution: Possibly that new parameter represented a brand new quantum area, and interactions with that area naturally produced the symmetry.
This was the axion, so named after a model of dishwashing detergent as a result of it cleaned up the mess of the symmetry downside.
If axions exist, they might make a superb darkish matter, as a result of they might be plentiful and hardly, if ever, work together with regular matter. And they might additionally do some wild issues.
Axions are extremely mild — trillions upon trillions of instances lighter than even the neutrino, the lightest recognized particle. With such slight plenty, their quantum wave nature would manifest at macroscopic scales. Whereas each particle additionally has a wave related to it, we normally do not discover or care about these waves until we’re coping with subatomic quantum programs. That is not so with the axion, which might probably unfold its wavelength throughout a complete galaxy.
The second cool factor about axions is that they’re bosons. Bosons are a sort of particle that may all share the identical quantum state, that means you’ll be able to stuff as lots of them right into a compact quantity as you need. That is just like photons (you’ll be able to put as a lot mild in a field as you need) and completely different from particles like electrons (you’ll be able to solely cram so many in earlier than the field will get full).
These two properties of axions imply that they’re exceptionally good at collapsing right down to extremely excessive densities, pulled collectively by their very own (slight) gravity. Basically, they will type a sort of star. It is fully invisible, radiates no mild and doesn’t work together with something, nevertheless it’s a star nonetheless.
These stars — which have a wide range of names, together with axion stars, boson stars and darkish stars — could be small, roughly the identical mass as regular, on a regular basis stars. They will also be enormous, spanning a complete galactic core.
The potential existence of boson stars is a double-edge sword. On one hand, it might probably make direct detection extraordinarily tough. Except a boson star simply occurs to be wandering by means of our photo voltaic system and passing by means of Earth, we’re unlikely to see axions in our detectors.
Then again, boson stars can do all types of issues that would make them detectable, like mess with nuclear fusion in stellar cores or blow up on their very own in an occasion referred to as a bosenova.
We do not know if axions exist or, in the event that they do, in the event that they’re liable for darkish matter. Nevertheless it’s nonetheless enjoyable to think about a universe teeming with silent, invisible, innocent darkish stars.
