What is "swart star"

Swart \Swart\, a. [OE. swart, AS. sweart black; akin to OFries, OS. & LG. swart, D. zwart, G. schwartz, OHG. swarz, Icel. svarir, Sw. svart, Dan. sort, Goth. swarts; cf. L. sordes dirt, sordere to be dirty. Cf. Sordid, Surd.]

1. Of a dark hue; moderately black; swarthy; tawny. ``Swart attendants.''
   --Trench. ``Swart savage maids.''
   --Hawthorne.

   A nation strange, with visage swart.
   --Spenser.

2. Gloomy; malignant. [Obs.]
   --Milton.

   Swart star, the Dog Star; -- so called from its appearing during the hot weather of summer, which makes swart the countenance. [R.]
   --Milton.