In a new first author study, astronomers have uncovered something remarkable hidden within the Galactic open cluster King 6. This star cluster is about 2360 light years away from Earth. The science team discovered 3 new variable stars. Because of this, they classified these stars as slow pulsating B-type (SPB) variables, which exhibit variability in magnitude and periodicity. This discovery sheds light on the dynamical and stellar content of King 6. At 251 million years old, it is the clearest case so far of mass segregation within the cluster.
Among the discovered stars are TIC 31624679716, TIC 31632068918 and TIC 3163212399. They all exhibit similar phase curve magnitude variations of about 0.02, 0.01, and 0.04 respectively. Their periods are 46.70, 47.92, and 37.56 hours respectively. This discovery adds to the understanding of the stellar characteristics within King 6 and enhances the knowledge of open clusters in general.
Key Characteristics of King 6
King 6 has a tidal radius of 10.37 light years and covers a radius of about 6.45 light years. The cluster has a steep mass function slope of ∼ 0.57. This means that it is expected to host a large variety of stellar masses. Researchers have observed that King 6 is dynamically relaxed making their structure even more stable, as indicated by their observation.
The temperature ranges of the stars in King 6 varies from 10,500 to 11,050 Kelvin. This broad range suggests that this cluster is composed of quite hot stars. King 6 has a modeled relaxation time of at least six million years. This interesting fact favors its classification as a dynamically relaxed open cluster.
Mass Segregation and Stellar Dynamics
To us, perhaps the most surprising, yet exciting finding from our research, is the obvious presence of mass segregation within King 6. The most massive stars tend to cluster more toward the center of the cluster. At the same time, the outer regions are filled with lighter stars. Such segregation is a fundamental part of understanding stellar evolution and dynamics within open clusters.
King 6 had previously exhibited a colour excess of 0.55. Its mass function slope was at a high of 1.29. This new discovery of variable stars provides extremely useful information. It illustrates how these features can shape the underlying architecture and dynamics of the cluster.
“Identification chart for the cluster King 6, taken from SDSS. Rectangular box outlines observed region, while the red circles highlight position of variable stars. Credit: arXiv (2025). DOI: 10.48550/arxiv.2504.18088”
Implications for Future Research
The discovery of these three variable stars opens new avenues for research on the nature of stellar populations in open clusters like King 6. Understanding the mechanisms behind their pulsations can lead to broader insights into stellar evolution, particularly regarding how different types of stars interact and evolve over time.
Moreover, these findings could contribute to refining models related to mass function slopes and color excesses in similar astronomical structures. Astronomers are now hard at work unlocking the secrets of King 6. Their discoveries will certainly uncover more information, which will further inform our understanding of this cluster and other Galactic open clusters individually and collectively as well.