• Source: NGC 6210

      • NGC 6210, sometimes also known as the Turtle Nebula, is a planetary nebula located in the constellation Hercules, approximately 5.4 ± 1.3 kly from the Sun. 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. 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".
      This nebula is "very amorphous and irregular" in shape, but forms a rough ellipsoid. 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. The emission from the outer part of the nebula is only about 1% of the total.
      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☉. 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.


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      External links



      HubbleSite NewsCenter Hubble picture and information on NGC 6210
      http://freestarcharts.com/constellations?catid=7&id=1:hercules-constellation-guide

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