Using a microwave probe of U.S. space agency NASA, scientists said they have evidence that the universe has a shape somewhat akin to an egg, rather than the expected round.
This would explain some curious anomalies over the universe's expanse, the scientists reported in the journal Physical Review Letters.
The researchers reached the conclusion by observing the universe with the Wilkinson Microwave Anisotropy Probe, which was launched by NASA in 2001 to measure fluctuations in the cosmic microwave background radiation.
The measurements of the probe agreed with a conventional spherical model of the observable universe, said the researchers. But when the data were measured on the largest scale, for instance taking in the entire night sky, the radiation was too low.
The Wilkinson Microwave Anisotropy Probe data have confirmed the anomaly concerning the low quadrupole amplitude compared to the best-fit Lambda-cold dark matter prediction, the researchers wrote in their paper.
"We show that by allowing the large-scale spatial geometry of our universe to be plane symmetric with eccentricity at decoupling or order 10-2," they added.
"The quadrupole amplitude can be drastically reduced without affecting higher multipoles of the angular power spectrum of the temperature anisotropy."
These anomalies may signal "a nontrivial cosmic topology" that is different from the sphere, indicated the researchers led by Leonardo Campanelli of the University of Ferrara in Italy.
They found that the radiation discrepancies disappeared if the universe was shaped like an ellipsoid, with an eccentricity of about one per cent.