Astronomers examined two old open clusters (OCs) known as NGC 1798 and NGC 1193 using the San Pedro Martir Observatory and data from the European Space Agency’s Gaia satellite. The study’s findings, which were published on the arXiv pre-print server on July 13, shed more light on the properties of these OCs.
OCs are groups of stars that are gravitationally bound to each other and formed from the same giant molecular cloud. More than 1,000 of them have been discovered so far in the Milky Way, and scientists are still looking for more in the hope of discovering a variety of these stellar groupings. Extending the list of known galactic OCs and studying them in depth could be critical for improving our understanding of our galaxy’s formation and evolution.
NGC 1798 was discovered in 1885 and is located 11,300 light years away in the constellation Auriga. It has a metallicity of -0.27 and is estimated to be 1.7 billion years old. NGC 1193 was discovered in 1786 in the constellation Perseus, at a distance of approximately 15,000 light years from Earth. Previous observations have revealed that NGC 1193 is about 8 billion years old and has a metallicity of -0.34.
A team of researchers led by Talar Yontan of Istanbul University in Turkey used the San Pedro Martir Observatory to conduct photometric, astrometric, and kinematic studies on the two OCs. Data from Gaia Early Data Release 3 supplemented the study (EDR3).
“These two clusters, as well as many others, were observed at the San Pedro Martir Observatory as part of an ongoing UBVRI photometric survey of Galactic stellar clusters. The Ritchey-Chretien 84-cm (f /15) telescope was used in conjunction with the Mexman filter wheel “The researchers elaborated.
Overall, the observations enabled the team to investigate the structure of NGC 1798 and NGC 1193. They discovered basic astrophysical parameters as well as galactic orbital properties for these two clusters.
The study discovered that both clusters have limiting radii of about 8 arcminutes. This value corresponds to limiting radii of NGC 1798 and NGC 1193 of 33.77 and 42.21, respectively. The astronomers stated that the stars within these limiting radii are considered potential cluster members and that their analysis is limited to this set of stars.
Overall, 428 and 361 stars were identified as most likely members of NGC 1798 and NGC 1193, respectively. Both OCs were discovered to be born outside the solar system, with birth radii of 35.4 light years for NGC 1193 and 38.5 light years for NGC 1798 from the Galactic centre. Furthermore, both clusters orbit in the Galactic disk’s metal-poor region.
NGC 1798 has a reddening of 0.5 mag and a photometric metallicity of -0.2, according to the new findings. The cluster was discovered to be younger than previously thought, with an estimated age of 1.3 billion years. The distance between NGC 1798 and Earth was calculated to be 14,500 light years.
When it comes to NGC 1193, its reddening is approximately 0.15 mag, and its metallicity is -0.3. This OC is approximately 18,100 light years away and was discovered to be younger than previously estimated—its age was determined to be 4.6 billion years.