New approach refines the Hubble's constant and age of universe

Date:
July 27, 2020
Source:
University of Oregon
Summary:
Using known distances of 50 galaxies from Earth to refine
calculations in Hubble's constant, astronomers estimates the age
of the universe at 12.6 billion years.



FULL STORY ========================================================================== Using known distances of 50 galaxies from Earth to refine calculations
in Hubble's constant, a research team led by a University of Oregon
astronomer estimates the age of the universe at 12.6 billion years.


========================================================================== Approaches to date the Big Bang, which gave birth to the universe, rely
on mathematics and computational modeling, using distance estimates of
the oldest stars, the behavior of galaxies and the rate of the universe's expansion. The idea is to compute how long it would take all objects to
return to the beginning.

A key calculation for dating is the Hubble's constant, named after
Edwin Hubble who first calculated the universe's expansion rate in
1929. Another recent technique uses observations of leftover radiation
from the Big Bang. It maps bumps and wiggles in spacetime -- the cosmic microwave background, or CMB - - and reflects conditions in the early
universe as set by Hubble's constant.

However, the methods reach different conclusions, said James Schombert,
a professor of physics at the UO. In a paper published July 17 in
the Astronomical Journal, he and colleagues unveil a new approach that recalibrates a distance-measuring tool known as the baryonic Tully-Fisher relation independently of Hubble's constant.

"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," Schombert said.

Schombert's team recalculated the Tully-Fisher approach, using accurately defined distances in a linear computation of the 50 galaxies as guides for measuring the distances of 95 other galaxies. The universe, he noted, is
ruled by a series of mathematical patterns expressed in equations. The new approach more accurately accounts for the mass and rotational curves of galaxies to turn those equations into numbers like age and expansion rate.



==========================================================================
His team's approach determines the Hubble's constant -- the universe's expansion rate -- at 75.1 kilometers per second per megaparsec, give
or take 2.3. A megaparsec, a common unit of space-related measurements,
is equal to one million parsecs. A parsec is about 3.3 light years.

All Hubble's constant values lower than 70, his team wrote, can be ruled
out with 95 percent degree of confidence.

Traditionally used measuring techniques over the past 50 years, Schombert
said, have set the value at 75, but CMB computes a rate of 67. The CMB technique, while using different assumptions and computer simulations,
should still arrive at the same estimate, he said.

"The tension in the field occurs from the fact that it does not,"
Schombert said. "This difference is well outside the observational errors
and produced a great deal of friction in the cosmological community." Calculations drawn from observations of NASA's Wilkinson Microwave
Anisotropy Probe in 2013 put the age of the universe at 13.77 billion
years, which, for the moment, represents the standard model of Big
Bang cosmology. The differing Hubble's constant values from the various techniques generally estimate the universe's age at between 12 billion
and 14.5 billion years.

The new study, based in part on observations made with the Spitzer Space Telescope, adds a new element to how calculations to reach Hubble's
constant can be set, by introducing a purely empirical method, using
direct observations, to determine the distance to galaxies, Schombert
said.

"Our resulting value is on the high side of the different schools of
cosmology, signaling that our understanding of the physics of the universe
is incomplete with the hope of new physics in the future," he said.


========================================================================== Story Source: Materials provided by University_of_Oregon. Original
written by Jim Barlow.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. James Schombert, Stacy McGaugh, Federico Lelli. Using the Baryonic
Tully-
Fisher Relation to Measure H o. The Astronomical Journal, 2020;
160 (2): 71 DOI: 10.3847/1538-3881/ab9d88 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200727114724.htm

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