Using a new approach, a team of scientists at the University of Oregon (UO), in the US, have come up with a new estimate for the age of the universe – 12.6-billion years. Since 2013, the generally accepted age of the universe has been 13.77-billion years. (This figure was derived using data from the US National Aeronautics and Space Administration’s Wilkinson Microwave Anisotropy Probe.)
The universe started with the Big Bang, and there have hitherto been two methods of calculating how long ago that was. Unfortunately, they have different outcomes.
Central to the question is Hubble’s Constant, named after renowned American astronomer Edwin Hubble, who, in 1929, was the first to calculate how fast the universe was expanding. Hubble’s Constant is thus the rate of expansion of the universe. But different methods give different numbers for it.
All attempts to date the universe depend on mathematics and computer modelling. The older method uses estimated distances to the oldest stars, the behaviour of galaxies and estimates of the Hubble Constant. This data is then used to calculate how long it would take for everything to go back to the moment of the Big Bang.
This approach suffers from what is called the ‘distance scale problem’. “The distance scale problem, as it is known, is incredibly difficult because the distances to galaxies are vast and the signposts for their distances are faint and hard to calibrate,” explains UO physics professor and research team leader James Schombert.
The other, more recent, approach is to employ observations of the cosmic microwave background (CMB), which is the radiation leftover from the Big Bang. The UO press release describes CMB as “bumps and wiggles in spacetime”. These variations reflect the conditions in the early universe, as established by Hubble’s Constant.
The traditional approach has resulted in Hubble’s Constant being set at 75 km per second per megaparsec. (A megaparsec is one million parsecs, while a parsec is some 3.3 light years.) But the CMB approach gives a figure for Hubble’s Constant of 67. Despite the differences in the assumptions and computer simulations between the two approaches, they should come up with pretty much the same values for the Constant.
“The tension in the field occurs from the fact that it does not,” he points out. “This difference is well outside the observational errors and produced a great deal of friction in the cosmological community.”
The UO team took a different tack, based on the fact that the universe is governed by mathematical patterns which can be stated in equations. They then used the known and accurately defined distances from Earth to 50 galaxies to undertake a linear computation of distances to 95 other galaxies. These calculations were then used to recalculate what is called the Tully-Fisher Relation (which is the correlation between the luminosity and speed of rotation of spiral galaxies, which allows the calculation of the distance of those galaxies from the Earth).
This new approach is purely empirical and uses direct observations to determine the distances to galaxies. It also provides more accurate data for the masses and rotational curves of the galaxies, to be incorporated into the equations, to produce numbers for Hubble’s Constant and the age of the universe.
As a result, the UP team has calculated Hubble’s Constant at 75.1 and determined that values for the Constant below 70 could be excluded with a confidence level of 95%. “Our resulting value is on the high side of the different schools of cosmology, signalling that our understanding of the universe is incomplete with the hope of new physics in the future,” observes Schombert.
The study was partly based on observations made using the Spitzer Space Telescope. The team’s findings were published in the Astronomical Journal.