IC 4665 - open cluster in Ophiuchus

  Size: 1800 px      
© Velimir Popov & Emil Ivanov 2017

The discovery of this open cluster is attributed to the Swiss astronomer Philippe Loys de Chéseaux, who observed it and inserted it into his catalog of "nebulous" objects published in 1746. Curiously, zhe cluster was not included in the Messier Catalog, although it had been discovered more than a quarter of a century before Charles Messier compiled it. Likewise, it was not reported by William Herschel, probably because of its size. We had to wait for the second Index Catalog to be published, this object to receive a catalog number. IC 4665 is a cluster that presents some special features: it has a very young age, estimated at around 35 million years, and is in an unusual position to be an open cluster, about 16 ° north of the galactic plane. This is evidence of the fact that the star formation environment in which it was generated had unusual features. However, this is not reflected in the chemical composition of the surface of its star members, as evidenced by a study conducted on ROSAT data. Estimates of age vary, however, depending on distance, which also has slight uncertainties. The estimates on the latter provide a value of 370 ± 50 parsec (1200 ± 160 light years). The cluster contains fifty stars brighter than magnitude 13; among them the brightest is a blue star of class B4V.The number of small mass stars, comprised between spectral classes F and M, would be 40, mostly detected by studying their radial velocity. Among the massive components, 19 are spectroscopic doubles ; the intense tidal forces between the two components of these star systems would explain the relatively slow rotation speed of the IC 4665 stars.

Image details:


Center of field RA 17:46:22 (h:m:s)
Center of field DE +05:43:42 (deg:m:s)
Size 1.76 x 1.21 (deg)
Pixel scale: 2.99 (arcsec/pixel)
Orientation: Up is 255 degrees E of N
Charts and image details obtained from Astrometry.net
Optic(s): ASA 12" Astrograph @ f/3.6 (Newton)
Mount: ASA DDM85 Standard
Camera: SBIG STL 11000 M
Filters: Luminance, Red, Green, Blue, Astronomik filters
Dates/Times: 26. Apr. 2017
Location: IRIDA Observatory, BG, longitude: E 24 44' 18", latitude: N 41 41' 42"
Exp. Details: L:3x3min., R:3x3 min, G:3x3 min, B:3x3 min, Bin 2, Total Exposure Time - 36 min.
More details: Dark and flat frames reduction
Processing: PixInsight / PS
Copyright: Velimir Popov and Emil Ivanov 2013 - 2017. All Rights Reserved
e-mail: info@irida-observatory.org
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