NGC 2509

NGC 2509 is an open cluster in the constellation of Puppis. It was discovered on 3 December 1783 by William Herschel.^[3] It was described as "bright, pretty rich, slightly compressed" by John Louis Emil Dreyer, the compiler of the New General Catalogue.^[3]

NGC 2509
DSS image of NGC 2509
Observation data (J2000 epoch)
Right ascension	08h 00m 48s[1]
Declination	−19° 03′ 06″[1]
Distance	9,500 ly (2,900 pc[1])
Apparent magnitude (V)	9.3[2]
Apparent dimensions (V)	2.5 ± 0.5′
Physical characteristics
Estimated age	1,200 Myr[1]
Other designations	NGC 2509, Cr 171, Mel 81, OCl 630[2]
Associations
Constellation	Puppis
See also: Open cluster, List of open clusters

The cluster is about 14 light-years (4.2 parsecs) wide,^[1] but the cluster's other parameters remain poorly known. Some studies have estimated a distance of about 9,500 light-years (2,900 parsecs) away from the Solar System,^[1] while older estimates put it at only 2980 light-years (912 parsecs) away.^[4] Estimates of the cluster's age have also varied significantly, from 1.2 billion years old^[1] to 8 billion years old.^[4] The latest analysis based on the parallaxes measured by the Gaia spacecraft confirms that it is a relatively distant object, with a distance between 2500 and 3000 parsecs.^[5]