Astronomers have investigated two young galactic open clusters: King 6 and NGC 1605. They used data from the TÃœBÄ°TAK National Observatory and ESA's Gaia satellite. Their findings were published on the pre-print server arXiv on October 31.
Open clusters are groups of stars loosely gravitationally bound to each other. They form from the same giant molecular cloud. Over 1,000 open clusters have been discovered in the Milky Way. Scientists are still looking for more, hoping to find a variety of these stellar groupings.
King 6 and NGC 1605 are located in the second Galactic quadrant. They have been studied for decades, but many of their properties remain uncertain or unknown. For example, there is a big discrepancy in the data when it comes to the age of the clusters. Some studies suggest that they may be as young as 40 million years, while some observations indicate that they may be even a few hundred million years older.
The distance to the clusters is also debated as the results point to 1,500–2,800 light years for King 6, and 3,700–10,800 for NGC 1605.
To learn more about these two OCs, a team of astronomers led by Sevinc Gokmen of the Florida Atlantic University in Boca Raton, Florida, analyzed the observational data from the 1-m T100 telescope at the TÃœBÄ°TAK National Observatory and from the Gaia Data Release 3 (DR3).
They identified 112 member stars of King 6 and 160 member stars of NGC 1605 by employing the Unsupervised Photometric Membership Assignment in Stellar Clusters (UPMASK) algorithm on the astrometric data from DR3. These stars were used to estimate astrophysical parameters of the two clusters.
The study found that King 6 is about 200 million years old and is located approximately 2,360 light years away from the Earth. The cluster has a radius of some 6.85 light years and its total mass is estimated to be 195 solar masses. The metallicity of King 6 was measured to be at a level of 0.02 dex.
When it comes to NGC 1605, the results indicate that the cluster is about 400 million years old and located 9,700 light years away. NGC 1605 turned out to be much larger and more massive than King 6—with a radius of approximately 29 light years and a total mass of 623 solar masses. The cluster's metallicity was found to be 0.01 dex.
By analyzing the orbits of King 6 and NGC 1605, the astronomers concluded that both OC belong to the young thin-disk population of the galaxy and formed outside the solar circle. They added that mass segregation is observed in the two clusters and that they are both dynamically relaxed.
These findings provide important insights into the properties and nature of King 6 and NGC 1605.
Journal Information: Gokmen et al, CCD UBV and Gaia DR3 Analyses of Open Clusters King 6 and NGC 1605, arXiv (2023). DOI: 10.48550/arxiv.2311.00054