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NGC 6210
NGC 6210, sometimes also known as the Turtle Nebula,[4] is a planetary nebula located in the constellation Hercules, approximately 5.4 ± 1.3 kly from the Sun.[2] It is positioned about 38° above the galactic plane at a vertical distance of about 3.3 kilolight-years (1 kpc) and thus has little extinction from intervening interstellar dust.[5] This object was first recorded as a star-like feature by Joseph Lalande on March 22, 1799. However, credit for the discovery of a nebula goes to Wilhelm Struve in 1825. John L. E. Dreyer described it as, "a planetary nebula, very bright, very small, round, disc and border".[6] This nebula is "very amorphous and irregular" in shape, but forms a rough ellipsoid.[5] It consists of two parts; a bright inner region filled with arches and filaments spanning 13″ × 16", and a larger and fainter outer volume that has a pair of "tubular" structures. The inner region has an expansion velocity ranging over 19–24 km/s.[2] The emission from the outer part of the nebula is only about 1% of the total.[5] The central star has an apparent visual magnitude of 12.66 and the spectrum matches a hydrogen-rich star of type O(H). It has an estimated temperature of 65,000 K. The abundances of the nebula suggest a low initial mass for the central star, probably ~0.9 M☉.[5] Outflow from this star has been measured with velocities of 2,180 km/s, and the estimated mass loss rate is 2.2×10−9 M☉ yr−1. There appears to be a collaminated jet feature to the northwest, suggesting the central star is ejecting material along two and possibly four such directions.[7] Gallery
References
External links Wikimedia Commons has media related to NGC 6210. |
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