As the atoms don't have an electric charge, they only produce a minimal force on the electron. However, the electron is slightly scattered at the neutral atoms, without even leaving its orbit, and the weak bond that is generated between the Rydberg atom and the atoms inside of it, tying them together, is known as the Rydberg polaron. The excitation was predicted by theorists at Harvard University in 2016 and confirmed in 2018 by spectroscopy in an experiment using a strontium Bose–Einstein condensate. Theoretically, up to 170 ordinary strontium atoms could fit closely inside the new orbital of the Rydberg atom, depending on the radius of the Rydberg atom and the density of the Bose–Einstein condensate. The theoretical work for the experiment was performed by theorists at Vienna University of Technology and Harvard University, while the actual experiment and observation took place at Rice University in Houston, Texas.