The Universe is expanding more quickly than predicted according to the latest expansion rate measurement. Can astronomers explain this phenomenon or are they missing something in the cosmological model?
In the 1920 s, Edwin Hubble made a revolutionary discovery. Not only are galaxies are spreading away from Earth, but they are also spreading away from each other. This is why the Universe is in a state of expansion. Around 20 years ago, researchers highlighted that the amount of galaxies leaking from the Milky Way appears to be increasing over time. In other words, the Universe is expanding but overtime this expansion process is speeding up. The Hubble Constant is a unit measurement that allows researchers to measure the Universe’s rate of expansion.
From 2009 to 2013, the Planck satellite mapped anisotropies of the cosmic microwave background (CMB) which is an ancient afterglow from 380,000 years after the Big Bang. Data taken from the Planck satellite measured the the Constant should reach 41.9 miles per second per megaparsec, with less than 1 percent uncertainty. However there are other ways to measure the Hubble Constant.
The Hubble Constant can also be measured using a “Standard Candle” which is an astrophysical object with an absolute magnitude. These objects include Cepheid Variables (star), planetary nebulae, and Type Ia supernovae. The known luminosity of these objects allow astronomers to make an calculation to find out the precise distance in which they are moving away from Earth and from one another.
A few months ago, this measurement technique revealed rather surprising results. In fact last year a Cepheid variable calculation measured the Universe expansion rate as 45.7 miles per second per megaparsec. What is more there is only a 1 in 5,000 chance these results are incorrect. However a recent calculation has made an even more precise Universe expansion rate measurement. Using another method with the Hubble Telescope, a team of astronomers have more accurately calculated the absolute brightness of 70 Cepheid variables in the Large Magellanic Cloud.
The Universe is expanding faster than predicted…but why?
Using the method stated above, researchers have calculated a new Hubble Constant of 46 miles per second per megaparsec. This is around 9% faster than the first calculations made by the Planck data. However more importantly, these results are accurate as there is only a 1 in 100,000 chance they are incorrect. Despite the almost certitude of these measurements, astronomers are still unable to “physically” explain these new results.
Several hypotheses have been put forward to try an explain these results. For example the Universe could be the victim of a density increase of black energy. This enigmatic force is meant to represent 70% of the Universe’s matter-energy density. It is also possible that black matter is interacting more forcefully with normal matter. Whether either of these hypothesis are correct, there is no definitive proof. As a result, astronomers are still very far from being able to explain this phenomenon.
In fact researchers are suggesting this could be a completely new type of physics. As astrophysicist Adam Riess of the Space Telescope Science Institute states “We are measuring something fundamentally different.” Astronomers are measuring the speed the Universe is expanding today but they are also predicting how fast the Universe should be expanding using physics of the early Universe. Adam Reiss concludes by saying, “If these values don’t agree, there becomes a very strong likelihood that we’re missing something in the cosmological model that connects the two eras.”