Scientists found that they are so round that if it was magnified to the size of the solar system, it would still appear spherical to within the width of a human hair.
Electrons, negatively-charged particles which orbit the nuclei, deviates from absolute roundness by less than less than 0.000000000000000000000000001cm.
This means that if it was magnified to the size of the solar system, it would still appear spherical to within the width of a human hair.
The Imperial College London study, which is most accurate measurement yet of the shape of the electron, looked at particles inside molecules called ytterbium fluoride.
Using a laser, the team made measurements of the motion of these electrons.
They looked for any distinctive wobbles which would suggest that the shape of the molecule was distorted – as would occur if the electrons were not perfectly round.
‘Conventionally, people think that the electron is round like a little ball,’ lead author Tony Hudson said.
The current best theory to explain the interactions of sub-atomic particles is known as the Standard Model.
According to this framework, the electron should be close to perfectly spherical.
But the Standard Model is incomplete. It does not explain how gravity works and fails to explain other phenomena observed in the Universe.
So physicists have tried to build on this model. One framework to explain physics beyond the Standard Model is known as supersymmetry.
However, this theory predicts that the electron has a more distorted shape than that suggested by the Standard Model. According to this idea, the particle could be egg-shaped.
Researchers stress that the new observation does not rule out super-symmetry. But it does not support the theory, according to Dr Hudson, whose study was published in the journal Nature.