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The finding chart for the 70 variable stars identified in the observed field of NGC 559 in the V band. The variables belonging to the cluster are shown with circles while variables belonging to the field population are shown by squares. Credit: Joshi et al., 2020.

Astronomers from India have conducted a long-term photometric variability survey of an open cluster known as NGC 559. As a result, they detected 70 new variable stars in the field of this cluster. The finding is presented in a paper published September 15 on the arXiv pre-print repository.

Star clusters offer excellent opportunities to study stellar evolution as they are collections of stars with similar properties, for instance, age, distance and initial composition. In particular, astronomers often search for variable stars in young and intermediate-age clusters, which could be crucial in advancing the understanding of pre-main-sequence (PMS) stars, and therefore the initial phases of stellar evolution.

Located at a distance of about 7,900 light years away from the Earth, NGC 559 is an open cluster estimated to be around 224 million years old. Previous observations of NGC 559 have identified 542 member stars and found that the cluster has a reddening at a level of 0.82 mag, and that its radius containing half the members is about 4.86 arcmin.