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  • The termdark matteris a placeholder for matter that we're almost certain must

  • be out there because we see the effects of its gravitational pull. But that's all we

  • see, so we don't know exactly what it is yet.

  • There are a lot of competing explanations, and one of them has raised a few eyebrows

  • recently because it could account for some unexpected experimental results.

  • Maybe most interesting of all, this dark matter candidate opens up the possibility that there

  • areghost starsout there in space.

  • I'm talking about dark bosons, hypothetical subatomic particles with a very low mass.

  • In the most widely accepted explanation for quantum phenomena, the standard model of particle

  • physics, bosons are force-carrying particles like photons and gluons.

  • They're a different category from fermions like electrons, protons, and neutrons and

  • they play by different rules.

  • While fermions have mass, bosons can have mass or be massless.

  • Fermions also obey the Pauli exclusion principle,

  • which states that no two fermions can occupy the same quantum state.

  • This means that fermions like electrons can't be in the same place with the same spin at

  • the same time. That's not true for bosons, which means several identical bosons can be

  • packed into the same spot. Because they can have mass and can occupy

  • the same space, it's possible that lots of dark bosons could gravitationally attract

  • each other and create an object with a mass comparable to a star.

  • A so-called boson star

  • would behave very differently from the stars made of ordinary matter that we're used to.

  • They wouldn't be capable of fusion, so they wouldn't be able to produce any light. Actually they

  • should be totally invisible, since light wouldn't interact with the particles and instead would

  • just pass straight through them, hence theghost starmoniker.

  • Although a ring of plasma could form around them and give them away. They could become

  • incredibly massive, as massive as the supermassive black holes that are at the center of most

  • galaxies. Some scientists have suggested that a boson star is actually what's at the center

  • of our own Milky Way.

  • A hypothetical dark boson could solve the big mystery of dark matter, namely how it

  • exerts a gravitational pull while remaining otherwise invisible. But of course a question

  • this big can't be put to bed without a mountain of evidence. For dark bosons there is, at best,

  • a little bitty pile of dirt.

  • Still, it's something, and some of that possible evidence came very recently from

  • some big-name experiments.

  • One of them is the XENON1T experiment in Italy. XENON1T is a big tank of liquid xenon inside

  • an enormous tank of water buried under a mountain. It's actually looking for an entirely different

  • dark matter candidate, called Weakly Interacting Massive Particles, or WIMPs.

  • Last summer though, the scientists examining data from the experiment announced they saw

  • an excess of electrons that WIMPs couldn't account for. It's possible dark bosons interacted

  • with the Xenon which would explain what the detectors picked up, but so could a more mundane

  • event like radioactive contamination in the experiment.

  • Another big name experiment that could be pointing to dark bosons is LIGO, the interferometer

  • that famously helped detect gravitational waves

  • from the merger of two black holes back in 2015.

  • Researchers noticed that one of the many collisions it has since detected was unlike the others.

  • It was missing an initial stage where the two black holes spiral around each other.

  • The scientists calculated if two unconnected black holes could achieve this with a head-on collision,

  • but the math didn't work out.

  • When the researchers substituted boson stars in place of black holes though, things clicked.

  • Still, we are a long way away from calling this case closed. Maybe other explanations

  • can better account for the odd results from XENON1T and LIGO. Or maybe these detectors

  • and the more advanced ones in the pipeline will produce more evidence of dark bosons.

  • Dark bosons might not be the end of dark matter either. Remember, bosons are force-carrying

  • particles, so maybe they're not dark matter itself but the way regular matter interacts

  • with some other particle that is dark matter.

  • There are still so many question marks, but the thought that there may be massive ghost

  • stars out in space that we have yet to see is a nice reminder that there is still so

  • much to discover and search for.

The termdark matteris a placeholder for matter that we're almost certain must

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B1 dark matter dark matter boson experiment gravitational

Our Universe May Be Full of Massive Dark Matter Stars

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    Summer posted on 2021/06/16
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