An international team of astronomers has used NASA's Kepler and ESA's Gaia spacecraft to investigate six giant stars in the open cluster NGC 6866. The study, published on the pre-print server arXiv, sheds new light on the properties of these giant stars and the cluster itself.
Open clusters are groups of stars that formed from the same giant molecular cloud. They are loosely gravitationally bound to each other, and can contain anywhere from a few dozen to a few thousand stars. More than 1,000 open clusters have been discovered in the Milky Way, and scientists are still looking for more.
NGC 6866 is a relatively young open cluster located in the constellation Cygnus. It is estimated to be between 480 and 780 million years old, and is located about 3,900 light-years from Earth.
The team of astronomers led by Karsten Brogaard of the University of Bologna in Italy used data from Gaia and Kepler to identify and study the six giant stars in NGC 6866. These stars are all in the helium-core burning phase, which means that they are fusing helium in their cores.
The study found that the six giant stars have a mean radius of about 10.1 solar radii and a mean mass of around 2.8 solar masses. This is significantly smaller than predicted by current one-dimensional stellar models.
The team also found that the six stars were found to be between 443 and 580 million years old. By comparing all the collected data to stellar-model isochrones, the age of NGC 6866 was estimated to be 430 million years. This is younger than previously thought.
The researchers say that future asteroseismic missions, like the planned ESA's High-precision AsteroseismologY of DeNse (HAYDN) stellar fields, have the potential to uncover more details regarding the properties of stars in NGC 6866 and in other young open clusters.
This study provides new insights into the properties of giant stars in open clusters. The results could help astronomers better understand the formation and evolution of these stellar systems.
Journal Information: K. Brogaard et al, An asteroseismic age estimate of the open cluster NGC 6866 using Kepler and Gaia, arXiv (2023). DOI: 10.48550/arxiv.2308.12731
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