A supervoid might have brought answers to important cosmic mysteries.
The largest known structure in the universes might just be a giant void – at least, evidence found by astronomers seems to point to that. While more observations are needed to confirm the discovery of the “supervoid”, it is likely that it can explain the origin of an enormous and abnormally cold region of the sky.
The “cold region” was spotted for the first time back in 2004 by NASA, and it can be observed with the Cosmic Microwave Background (CMB). Its existence has so far remained unexplained in spite of the growing amount of literature constituting of possible theories, many of which are contradictory to others. The new study has focused on one of the hypotheses put forward in the past involving a supervoid.
An international team of astronomers, with lead author Istvan Szapudi from the Institute for Astronomy at The University of Hawaii at Manoa, have come up with evidence of a supervoid. It is said that the density of galaxies in a supervoid is much lower than what is considered to be usual in the known universe.
The team of researchers made use of two groups of data by matching objects spotted at infrared wavelengths by Nasa’s Wide Field Survey Explorer (WISE) with colours in visible light measured by the robotic telescope Pan-STARRS1. A map of the distribution of galaxies located in the cold region was thus made.
It was found that in the center of the cold spot, there was a decrease in the number of galaxies. This suggests the presence of the largest known structure in the universe: the supervoid. The supervoid is said to stretch 1.8 billion light years across heaven when the universe was 11.1 billion years old.
The universe would consist of holes, voids that are devoid of matter and gravitational pull. Were a photon from the CMB to meet a void, it would lose its energy to ultimately retrieve it upon exiting the void. Now, given that the universe is forever expanding, the photon would only exit in a medium less dense than before it entered the void. Lower density is, in turn, associated with weaker gravitational pull exerted on the photon exiting the hole. As a consequence, the photon would not be able to compensate for the totality of the energy it lost, and it would end up with less energy. Less energy is associated with a lower temperature. Therefore, that photon would have less energy and lower temperature than light from other regions of the sky where it would not pass through voids.
The cold spot in question is actually 70 μK colder than the chilly CMB radiation in the surroundings, which is 2.7 K. The fluctuations that do exist are very small: the temperature would differ by only around 18μK.
More observations need to be made to create enhanced maps of the supervoid in order to have additional information. For instance, it is not known if it has any substructure given the limited data.