A new study on globular clusters, a group of stars orbiting a core, support theories that the Universe came to be over 13 billion years ago.
392007 01: This image recorded by the Hubble telescope on July 10, 2001 shows two clusters of stars, called NGC 1850, located in a neighboring galaxy called the Large Magellanic Cloud.
The study, submitted to the Journal of Cosmology and Astroparticle Physics, inquired about the clusters in an attempt to determine the age of the Universe. Titled "Inferring the Age of the Universe with Globular Clusters," the research team was led by David Valcin from the Institute of Cosmos Sciences at the University of Barcelona (ICCUB) in Spain.
The multinational team included members from France's Sorbonne Universite and the US' Johns Hopkins University , in addition to the Spanish researchers from ICCUB and the Catalan Institution for Research and Advanced Studies. Representatives from the Flatiron Institute Center for Computational Astrophysics are also involved in the study.
A Novel Approach to Estimating Globular Cluster Age
In the study, researchers present their estimate for 68 galactic globular clusters. They utilized the distribution of the stars in each cluster through the full color-magnitude diagram. Among the criteria they used include distance, reddening, and metallicity.
They were able to examine the clusters through the Hubble Space Telescope's Advanced Camera for Survey (ACS). Data from the stars in each cluster were modeled through using a modified version of isochrones.
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Prior research on estimating the age of these globular clusters were also used, with their derived measurements agreeing with previously-published reports on the matter. The ICCUB-led research team, however, used the color-magnitude diagram to arrive at the age estimates. In comparison, previous estimates are taken through GAIA, which uses main-sequence dwarf stars instead. The team also used the Mesa Isochrones and Stellar Tracks (MIST) stellar model and the Dartmouth Stellar Evolution Database (DSED).
Linking Globular Cluster and Universe Age
After evaluating the 68 globular clusters, they arrived at an age estimate of 13.35 billion years. The result they presented stands at a 68% confidence level, and an uncertainty range of ±0.16 billion years for statistical uncertainty and ±0.5 billion years for systematic. From the data gathered, the oldest globular clusters are those with lower metallicity.
The study used the age of the oldest stars to determine a baseline for determining the age of the Universe. The result supports previously-published reports from the Planck mission on Cosmic Microwave Background (CMB) - background radiation all across the universe that is believed to have existed since The Big Bang.
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Furthermore, the Planck estimate on the age of the universe follows the Lambda - Cold Dark Matter (Lambda-CDM) cosmological model. The agreement between the globular cluster aging and the Planck estimate both narrow down the possible age of the Universe without building entirely on theoretical models.
However, the researchers recognize the need to identify discrepancies between different attempts to define the age of the Universe. David Valcin from the ICCUB said: "In the on-going uncertainty about the expansion of the Universe, it is important to collect more data which interpretation is as cosmology-independent as possible, to understand the origin of the discrepancy." He added that while globular clusters do not directly pinpoint the rate of expansion, it provides an idea about the age of the Universe.
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