Detailed study of the young open star cluster Messier 39

Italian astronomers conducted high-resolution spectroscopic observations of a young open star cluster named Messier 39.The results of the observation campaign were published in a paper posted on a preprint server on December 14 arXivyielding important information about the chemical composition of the clusters.

Open clusters (OCs) are groups of stars loosely gravitationally bound to each other, formed from the same giant molecular cloud. So far, more than 1,000 such star groups have been discovered in the Milky Way, and scientists are still looking for more, hoping to find various such star groups. Expanding the list of known galactic open clusters and studying them in detail is critical to improving our understanding of the formation and evolution of the Milky Way.

Messier 39 (or M39 for short, also known as NGC 7092) is a young galactic open star cluster located about 1,000 light-years away in the constellation Cygnus. The cluster has a linear tidal radius of 28 light-years, a mass of approximately 232 solar masses, and an estimated age of approximately 280 million years.

However, although Messier 39 was discovered nearly three centuries ago, it has not yet been observed with high-resolution spectrometers, and its chemical composition remains unknown. That’s why a team of astronomers led by Javier Alonso-Santiago of the Catania Astrophysical Observatory in Italy decided to use the Northern Hemisphere Spectrograph High-Precision Radial Velocity Planet Searcher (HARPS-N) and fiber optic Observe this cluster. Fed Echelle Spectrometer (FIES).

“We focused on M 39, a nearby young open cluster that has been little studied in recent years and whose chemical composition is so far unknown. We used the HARPS-N and FIES spectrographs to conduct high-resolution analyzes of 20 possible cluster members. resolution spectral analysis, supplemented by archival photometry and Gaia DR3 data,” the researchers explain.

First, the team identified 260 possible members of Messier 39 within a radius of 250 arcminutes around the nominal cluster center. It turns out that the three identified members are two-line spectral binary systems and there are no evolved stars in this sample. By examining the spatial distribution of these members, the distance to Messier 39 was inferred to be approximately 980 light-years.

The astronomers managed to derive the radial velocities and projected rotational velocities of the stars in the sample. They found that the rotation speed of most stars is between 6 and 3 km/s, and the average radial speed of Messier 39 was calculated to be 5.46 km/s. They also estimated the extinction and atmospheric parameters of these stars.

The study’s authors conducted chemical analyzes of the nine coolest stars in the sample (effective temperatures below 7,100 K) and determined the abundance of 21 elements. They found that Messier 39 has a solar-like metallicity (0.04 dex) and that the stars studied have a chemical composition similar to that of the Sun.

The researchers noted that only sodium showed lower abundance in the samples studied, while sulfur and the heaviest elements, especially barium, showed higher abundance. In addition, Messier 39 was also found to display a solar-like average ratio of alpha and iron peak elements to iron, with a slight excess for neutron capture elements.

Based on these results, the scientists concluded that the cluster’s chemical composition is completely compatible with that of the Milky Way’s thin disk.

2023 Science X Network