NGC 1605 is an open cluster of stars in the northern constellation of Perseus. It was discovered by German-British astronomer William Herschel on December 11, 1786. This cluster is located at a distance of approximately from the Sun. It spans an angular size of with an apparent visual magnitude of 11.0.
Observations This cluster has a low concentration with a Trumpler class of III 2 m. It is estimated to have 623 times the mass of the Sun with a core radius of . The cluster is drifting closer to the Sun with a line of sight velocity component of . It is a member of the young thin disk population of the Milky Way.
In 2021, D. Camargo presented results that suggested NGC 1605 is actually a binary open cluster system. The data showed two distinct stellar populations in the region: NGC 1605a with an age of 600 Myr and NGC 1605b at an age of 2 Gyr. This large age difference seemed to indicate a close encounter between two clusters that resulted in tidal capture. The presence of possible tidal debris appeared to support this hypothesis. However, a 2022 study of Gaia 3 data contradicted this finding, suggesting the apparent difference was the result of contamination by field stars.
The open cluster Can Batlló 1 may be located less than from NGC 1605.
References See p. B5.