919 Ilsebill ( prov. designation: A918 UD or 1918 EQ) is a dark background asteroid from the central region of the asteroid belt. It was discovered on 30 October 1918, by astronomer Max Wolf at the Heidelberg-Königstuhl State Observatory in southwest Germany. ^[1] The carbonaceous C-type asteroid has a short rotation period of 5.0 hours and measures approximately 33 kilometers (21 miles) in diameter. It was named after "Ilsebill", a character in the fairy tale The Fisherman and his Wife by the Brothers Grimm. ^[2]

Orbit and classification

Ilsebill is a non- family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. ^{[4] [5]} It orbits the Sun in the central asteroid belt at a distance of 2.5–3.0  AU once every 4 years and 7 months (1,686 days; semi-major axis of 2.77 AU). Its orbit has an eccentricity of 0.08 and an inclination of 8 ° with respect to the ecliptic. ^[3] The body's observation arc begins at Heidelberg Observatory with its official discovery observation on 30 October 1918. ^[1]

Naming

This minor planet was named after the character "Ilsebill" in the fairy tale The Fisherman and his Wife (German: Von dem Fischer und seiner Frau) by the Brothers Grimm. The asteroid was named likely after the discoverer's death in 1932, upon a proposal made by his widow Gisela Wolf, and subsequently published by ARI ( RI 1013). The naming was also mentioned in The Names of the Minor Planets by Paul Herget in 1955 ( H 89). ^[2]

Physical characteristics

In the Bus–Binzel SMASS classification and in the SDSS-based taxonomy, Ilsebill is a common, carbonaceous C-type asteroid. ^{[3] [5] [10]}

Rotation period

In October 2010, a rotational lightcurve of Ilsebill was obtained from photometric observations by Zachary Pligge, Ben Hall and Richard Ditteon at the U.S. Oakley Observatory ( 916) in Indiana. Lightcurve analysis gave a well-defined rotation period of 5.0325±0.0011 hours with a brightness variation of 0.25±0.02 magnitude ( U=3). ^[9] In September 2010, a similar, though lower rated period of 5.034±0.0010 hours with an amplitude of 0.24 was determined by astronomers at the Palomar Transient Factory in California ( U=2). ^{[11] [12]}

A modeled lightcurve using photometric data from the Lowell Photometric Database and from the Wide-field Infrared Survey Explorer (WISE) was published in 2018. It gave a concurring sidereal period of 5.03348±0.00002 hours and includes a partial spin axis at (β₁ = −53.0°) in ecliptic coordinates (λ, β). ^[13]

Diameter and albedo

According to the survey carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and the NEOWISE mission of NASA's WISE telescope, Ilsebill measures (27.65±1.7), (33.41±0.49) and (33.500±0.071) kilometers in diameter and its surface has a low albedo of (0.0698±0.010), (0.048±0.002) and (0.047±0.010), respectively. ^{[6] [7] [8]} The Collaborative Asteroid Lightcurve Link derives its estimate from IRAS, that is, an albedo of 0.0638 and a diameter of 27.62 km based on an absolute magnitude of 11.4. ^[11] Further published mean-diameters by the WISE team include (29.37±9.40 km), (32.598±7.912 km), (33.17±0.16 km), (34.444±0.254 km) and (38.64±12.97 km) with albedos between (0.027±0.046) and (0.05±0.03). ^{[5] [11]}

References

External links

• Lightcurve Database Query (LCDB), at www.minorplanet.info
• Dictionary of Minor Planet Names, Google books
• Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
• 919 Ilsebill at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 919 Ilsebill at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters