| Discovery[1] | |
|---|---|
| Discovered by | M. F. Wolf |
| Discovery site | Heidelberg Obs. |
| Discovery date | 28 April 1916 |
| Designations | |
| (826) Henrika | |
Named after | unknown[2] |
| A916 HD · 1930 MG 1934 HE · 1935 SW1 1948 PJ1 · 1957 QC 1962 UK · 1962 VC 1916 ZO | |
| Orbital characteristics[3] | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 103.52yr (37,809 d) |
| Aphelion | 3.2705AU |
| Perihelion | 2.1532 AU |
| 2.7119 AU | |
| Eccentricity | 0.2060 |
| 4.47 yr (1,631 d) | |
| 51.962° | |
| 0° 13m 14.52s / day | |
| Inclination | 7.1048° |
| 230.22° | |
| 36.697° | |
| Physical characteristics | |
| 5.9846±0.0001 h[9][a] | |
| 11.6[1][3] | |
826 Henrika (prov. designation:A916 HDor1916 ZO) is abackground asteroid from the central regions of theasteroid belt. It was discovered by German astronomerMax Wolf at theHeidelberg-Königstuhl State Observatory on 28 April 1916.[1] The carbonaceousC-type asteroid has arotation period of 5.98 hours and measures approximately 21 kilometers (13 miles) in diameter. Any reference to the origin of the asteroid's name is unknown.[2]
Henrika is a non-family asteroid of the main belt'sbackground population when applying thehierarchical clustering method to itsproper orbital elements.[4][5] It orbits the Sun in thecentral asteroid belt at a distance of 2.2–3.3 AU once every 4 years and 6 months (1,631 days;semi-major axis of 2.71 AU). Its orbit has aneccentricity of 0.21 and aninclination of 7° with respect to theecliptic.[3] The body'sobservation arc begins atHeidelberg Observatory on 2 July 1921, more than five years after its official discovery observation.[1]
Any reference of thisminor planet's name to a person or occurrence is unknown.[2]
Among the many thousands ofnamed minor planets,Henrika is one of 120 asteroids for whichno official naming citation has been published. All of these asteroids have low numbers, the first one being164 Eva. The last asteroid with a name of unknown meaning is1514 Ricouxa. They were discovered between 1876 and the 1930s, predominantly by astronomersAuguste Charlois,Johann Palisa,Max Wolf andKarl Reinmuth.[11]
In the Bus–BinzelSMASS classification,Henrika is a common, carbonaceousC-type asteroid,[3][5] with an untypically highalbedo(see below) for suchspectral class. In a taxonomic classification based on MOVIS near-infrared colors,Henrika could not be assigned a final class and was labelled as undefined (U).[10]
In April 210, a rotationallightcurve ofHenrika was obtained from six nights ofphotometric observations byFrederick Pilcher at the Organ Mesa Observatory (G50) in New Mexico. Analysis of the classically shaped bimodal lightcurve gave a well-definedrotation period of5.9846±0.0001 hours with a brightness variation of0.26±0.02magnitude (U=3).[9][a] During the same apparition, a virtually identical period of5.9840±0.0003 hours with an amplitude of0.26±0.02 magnitude (U=3) was determined by Kenda Albers and colleges of theRose-Hulman Institute of Technology at the Oakley Southern Sky Observatory (E09) in Australia.[12]
According to the surveys carried out by the Infrared Astronomical SatelliteIRAS, and the JapaneseAkari satellite, and theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer (WISE),Henrika measures (19.28±2.3), (21.83±0.43) and (22.556±0.258) kilometers in diameter and its surface has analbedo of (0.1435±0.042), (0.114±0.005) and (0.166±0.025), respectively.[6][7][8]
Alternative mean-diameters published by the WISE team include (14.92±4.26 km), (20.44±0.58 km) and (24.119±0.254 km) with corresponding albedos of (0.14±0.16), (0.07±0.01) and (0.0917±0.0172).[5] TheCollaborative Asteroid Lightcurve Link derives an albedo of 0.1103 and a diameter of 19.15 kilometers based on anabsolute magnitude of 11.6.[13] Anasteroid occultations ofHenrika from 19 January 2010, gave a best-fit ellipse dimension of (19.0 km × 19.0 km).[5] These timed observations are taken when the asteroid passes in front of a distant star.
