1384 Kniertje, provisional designation 1934 RX, is a dark Adeonian asteroid from the central regions of the asteroid belt, approximately 26 kilometers in diameter. It was discovered on 9 September 1934, by Dutch astronomer Hendrik van Gent at the Union Observatory in Johannesburg, South Africa.^[19] The asteroid was named after a character in the Dutch play Op Hoop van Zegen by Herman Heijermans.^[2]

Kniertje is a member of the Adeona family (505),^[4] a large family of carbonaceous asteroids in the central main belt, named after 145 Adeona. It is also dynamically classified as a member of the Eunomia family (502), the largest in the intermediate main belt with more than 5,000 stony asteroids.^{[3][16]: 23}

The asteroid orbits the Sun in the central asteroid belt at a distance of 2.2–3.2 AU once every 4 years and 5 months (1,599 days). Its orbit has an eccentricity of 0.18 and an inclination of 12° with respect to the ecliptic.^[1] The body's observation arc begins with its official discovery observation at Johannesburg in 1934.^[19]

Kniertje's spectral type is unknown. Although the LCDB assumes an S-type (due to its dynamical classification to the stony Eunomia family), a low albedo of 0.0701 is derived (see below) which is typical for carbonaceous C-type asteroids and in agreement with the overall spectral type of the Adeona family (505).^{[3][16]: 23}

Several rotational lightcurves of Kniertje have been obtained from photometric observations since 2003. Lightcurve analysis gave a rotation period between 9.78 and 9.872 hours with a brightness variation between 0.15 and 0.32 magnitude (U=2/2/2/2/2).^[12][13][14] An alternative period solution of 12.255 hours with an amplitude of 0.33 magnitude was found by Brian Warner in March 2006 (U=2).^[15][a]

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Kniertje measures between 21.52 and 29.592 kilometers in diameter and its surface has an albedo between 0.0351 and 0.3077.^{[5][6][7][8][9][10][11]}

The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0701 and a diameter of 26.59 kilometers based on an absolute magnitude of 11.38.^[3]

This minor planet was named after the principal character in Op Hoop van Zegen, a play by Dutch writer Herman Heijermans (1864–1924). The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 125).^[2]

• Asteroid Lightcurve Database (LCDB), query form (info Archived 16 December 2017 at the Wayback Machine)
• Dictionary of Minor Planet Names, Google books
• Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 1384 Kniertje at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 1384 Kniertje at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters