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RE: NGC 1980
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NGC 1980 (also OCl 529 and LBN 977) is a magnitude +2.5 open star cluster and gas nebula located 1790 light-years away in the constellation Orion. 
The cluster is less than one degree south of the Orion nebula, and consists of 2000 young hot blue stars of spectral type O and B with an age of about 4-5 million years. The brightest star of the cluster, Iota Orionis, is visible to the naked eye.
NGC 1980 belongs to the Orion OB1 association, a vast association that includes at least 10,000 stars, located at an average distance of about 1400 light-years away.

The best time to observe the cluster is in the evening sky between October and March.

The cluster was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Clayhall Farm House in Old Windsor on the 31st January 1786.

Right ascension 05h 35m 25.0s, Declination -05° 54' 54"



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OCl 529
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Title: Characterizing the stellar population of NGC 1980
Author: Marina Kounkel, Lee Hartmann, Nuria Calvet, Tom Megeath

NGC 1980 is a young cluster that is located about 0.5 degrees south of the Orion Nebula Cluster (ONC). Recent studies by Bouy et al. and Pillitteri et al. have suggested that NGC 1980 contains an older population of stars compared to a much younger ONC, and that it belongs to a foreground population that may be located in front of the Orion A molecular gas by as much as 40 pc. In this work we present low-resolution spectra towards 148 young stars found towards the NGC 1980 region. We determine the spectral types of these stars, examine accretion signatures and measure the extinction towards them. We determine that based on these observations, the age of the population of NGC 1980 is indistinguishable from L1641, estimated to be ~3 Myr, comparable with the study by Fang et al.

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Title: NGC 1980 is not a foreground population of Orion: Spectroscopic survey of young stars with low extinction in Orion A
Author: Min Fang, Jinyoung Serena Kim, Ilaria Pascucci, Dániel Apai, Lan Zhang, Aurora Sicilia-Aguilar, Miguel Alonso-Martínez, Carlos Eiroa, Hongchi Wang

We perform a spectroscopic survey of the foreground population in Orion A with MMT/Hectospec. We use these data, along with archival spectroscopic data and photometric data, to derive spectral types, extinction values, and masses for 691 stars. Using the Spitzer Space Telescope data, we characterize the disk properties of these sources. We identify 37 new transition disk (TD) objects, one globally depleted disk candidate, and 7 probable young debris disks. We discover an object with a mass less than 0.018-0.030 solar masses, which harbors a flaring disk. Using the H alpha emission line, we characterize the accretion activity of the sources with disks, and confirm that fraction of accreting TDs is lower than that of optically thick disks (46±7% versus 73±9%, respectively). Using kinematic data from the Sloan Digital Sky Survey and APOGEE INfrared Spectroscopy of Young Nebulous Clusters program (IN-SYNC), we confirm that the foreground population shows similar kinematics to their local molecular clouds and other young stars in the same regions. Using the isochronal ages, we find that the foreground population has a median age around 1-2 Myr, which is similar to the one of other young stars in Orion A. Therefore, our results argue against the presence of a large and old foreground cluster in front of Orion A

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Title: Orion Revisited - I. The massive cluster in front of the Orion Nebula Cluster
Authors: J. Alves, H. Bouy

The aim of this work is to characterise the stellar population between Earth and the Orion A molecular cloud where the well known star formation benchmark Orion Nebula Cluster (ONC) is embedded. We use the denser regions the Orion A cloud to block optical background light, effectively isolating the stellar population in front of it. We then use a multi-wavelength observational approach to characterise the cloud's foreground stellar population. We find that there is a rich stellar population in front of the Orion A cloud, from B-stars to M-stars, with a distinct 1) spatial distribution, 2) luminosity function, and 3) velocity dispersion from the reddened population inside the Orion A cloud. The spatial distribution of this population peaks strongly around NGC 1980 (iota Ori) and is, in all likelihood, the extended stellar content of this poorly studied cluster. We infer an age of ~4-5 Myr for NGC 1980 and estimate a cluster population of the order of 2000 stars, which makes it one of the most massive clusters in the entire Orion complex. What is currently taken in the literature as the ONC is then a mix of several intrinsically different populations, namely: 1) the youngest population, including the Trapezium cluster and ongoing star formation in the dense gas inside the nebula, 2) the foreground population, dominated by the NGC 1980 cluster, and 3) the poorly constrained population of foreground and background Galactic field stars. Our results support a scenario where the ONC and L1641N are not directly associated with NGC 1980, i.e., they are not the same population emerging from its parental cloud, but are instead distinct overlapping populations. This result calls for a revision of most of the observables in the benchmark ONC region (e.g., ages, age spread, cluster size, mass function, disk frequency, etc.).

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