Kapteyn's Star

0.004 L ☉

Kapteyn's star is a sun nearby star of the class of the red subdwarfs. Its mass is only 38% of the sun's mass and its size almost 3 Jupiter diameter. Its luminosity is only about one thousandth of the solar luminosity. The star is located in the constellation of painters ( Pictor ), and is visible as a faint object only in the light telescope. Due to its location in the southern sky, it can be observed only south of 45 degrees north latitude. The age of the star is estimated at 13 billion years.

The celestial body is considered erdnächstes object of this rare type of halo stars and thus deviates strongly from the usual direction of movement from Stern: It moves in a retrograde irregular, elliptical orbit around the Milky Way. This also explains its very high proper motion, the second largest after Barnard's Star - he is one of the fast runners. Firmament, the movement runs to the southeast, so that the distance to the solar system continually increasing.


Kapteyn's star was discovered in 1897 by the Dutch astronomer Jacobus Kapteyn C. photometrically. The photographic plates taken at the Cape of Good Hope Royal Observatory of David Gill and served the systematic creation of a star catalog ( Cape Photographic survey ). At the time of its discovery Kapteyn's star had the largest proper motion of all stars and thus replaced the former record holder Groombridge 1830. With the discovery of Barnard's Star 1916, he was replaced in that position.

Cosmic environment and origin

The celestial body is one of the 30 stars closest to the Sun. At the present time (2009) there is no evidence for exoplanets present in its environment. The nearest star at a distance of nearly 4 light years is the red subdwarf LHS 1565 / FY 1061, and more are in Sirius 6.5 and Epsilon Eridani at 7.5 light years away. According to recent findings of the heavenly bodies and other stars of the so-called Kapteynschen group of motions of a spherical dwarf galaxy that merged billions of years ago with the Milky Way comes from. The stars of the galaxy were pulled apart at a stellar stream, an elongated trail of stars with similar motion in the Milky Way. Only the compact core of the dwarf galaxy was left, which now forms the globular cluster Omega Centauri.


The star belongs to the spectral class M whose characteristic is a strong titanium oxide ( TiO ) band. The celestial body has as eruptive variable star, a variable spectrum. He belongs to the type of flare stars (UV Ceti stars). A characteristic of this type of star that is often found in the solar neighborhood, faint stars, are monumental, unpredictable gas eruptions on the surface, the change in the short term the luminosity strong. The H line is at 656.8 nm compared to the laboratory value increased wavelength shows that the object is moved away from the solar system (optical Doppler effect). The peculiarity in his star's spectrum is the relative gain of the Ca -I and Cr I lines relative to the strength of the TiO bands. The concentration of heavy elements - its metallicity - compared to solar-type stars small, within its class but normal. Because of the relative proximity of the celestial body and the associated good signal -to-noise ratio of the spectral observations also open statements about a large number of similar, but much more distant and thus less accessible analysis of stars.

References =