中山增一

武仙座ξ，又名BD+29 3156，HD 163993、SAO 85590、HR 6703，是武仙座的一颗恒星，视星等为3.7，位于银经54.91，银纬23.77，其B1900.0坐标为赤经17h 53m 52.7s，赤纬+29° 23.77′ 31″。

Xi Herculis is a solitary star located within the northern constellation of Hercules. The star is visible to the naked eye with an apparent visual magnitude of 3.70. Based upon an annual parallax shift of 23.85 mas as seen from Earth, it is located 137 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.05 due to interstellar dust. It is a suspected member of the Sirius stream of co-moving stars.

This is an evolved G-type giant star with a stellar classification of G8 III. It is a red clump star, which means it is on the horizontal branch and generating energy through the thermonuclear fusion of hydrogen at its core. The star is emitting X-rays with a luminosity of 3.03×10³⁰ erg s⁻¹ in the 0.3–10 keV band. It has twice the mass of the Sun but, at the age of two and a half billion years, it has expanded to 10 times the Sun's radius. The star is radiating 57 times the solar luminosity from its photosphere at an effective temperature of 5,032 K.

Xi Herculis was discovered to be a variable star when the Hipparcos data was analyzed. It is a semiregular variable star, oscillating in brightness by 3 hundredths of a magnitude, over a period of 120.8 days.

Chinese name

In R. H. Allen's book Star Names: Their Lore and Meaning, this star, together with ν Her and 99 Her (b Herculis) represent the state of Zhongshan (or Chung Shan, "the Middle Mountain"), but in Chinese literature, that name is applied to ο Her.

Markov 1, the mini teapot

One third of a degree to the north-northwest of Xi Herculis is the location of a telescopic asterism in the shape of a teapot. This teapot (Markov 1) could be seen as a somewhat twisted small equivalent of the large and easy to recognize teapot asterism in the constellation Sagittarius.