Scientists have long tried to explain the origin of a mysterious, large and anomalously cold region of the sky. In 2015, they came close to figuring it out as a study showed it to be a “supervoid” in which the density of galaxies is much lower than it is in the rest of the universe. However, other studies haven’t managed to replicate the result.
Now new research led by Durham University, submitted for publication in the Monthly Notices of the Royal Astronomical Society, suggests the supervoid theory doesn’t hold up. Intriguingly, that leaves open a pretty wild possibility – the cold spot might be the evidence of a collision with a parallel universe. But before you get too excited, let’s look at how likely that would actually be.
The cold spot can be seen in maps of the “cosmic microwave background” (CMB), which is the radiation left over from the birth of the universe. The CMB is like a photograph of what the universe looked like when it was 380,000 years old and had a temperature of 3,000 degrees Kelvin. What we find is that it is very smooth with temperature deviations of less than one part in 10,000. These deviations can be explained pretty well by our models of how the hot universe evolved up to an age of 380,000 years.