A scientific study which claims to show the Milky Way and its neighbouring galaxies exist in a celestial void, may have solved a problem that has puzzled scientists trying to establish the rate at which the universe is expanding.
University of Wisconsin-Madison student Ben Hoscheit gave a presentation to the 230th meeting of the American Astronomical Society on Tuesday, in which he argued the Milky Way and neighbouring regions contained far less density of stars, planets and galaxies than surrounding regions of space.
Mr Hoscheit and his supervisor, Amy Barger, said the findings could help explain the difference between estimates of the speed of the expansion of the universe astrophysicists get when they use different techniques of measurement.
The measurement of the rate at which the universe is expanding, described by a unit called the Hubble Constant, has been inconsistent between a technique which uses the light emitted from the explosion of a nearby supernovae at a known distance, compared with another based on cosmic microwave background — the leftover light from the Big Bang.
But Mr Hoscheit and Ms Barger argued it may be explained by the difference in gravitational pull being exerted between regions of low and high concentrations of matter inside and outside our galactic neighbourhood.
“No matter what technique you use, you should get the same value for the expansion rate of the universe today,” Mr Hoscheit told the University of Wisconsin.
The idea the universe is comprised of voids and filaments — dense superclusters of galaxies — is not new. Mr Hoscheit’s supervisor said his observations supported a previous hypothesis proposed by Ms Barger and another student, Ryan Keenan, that the Milky Way existed in a void at least seven times as large as average and with a radius of about 1 billion light years.
A metaphor that has been used is that if the universe was a block of Swiss cheese, the Milky Way was residing in one of the holes.
But Ms Barger said Mr Hoscheit’s findings may clear up the uncertainty that has plagued astrophysicists who have produced consistent expansion-rate estimates within, but not between the measurement techniques.
“What Ben has shown is that the density profile that Keenan measured is consistent with cosmological observables,” Ms Barger told the University of Wisconsin-Madison.
“One always want to find consistency, or else there is a problem somewhere that needs to be resolved.”