1080 Orchis

1080 Orchis, provisional designation 1927 QB, is a dark background asteroid from the inner regions of the asteroid belt. It was discovered on 30 August 1927, by German astronomer Karl Reinmuth at the Heidelberg Observatory in southwest Germany.^[18] The carbonaceous F-type asteroid has a rotation period of 16.1 hours and measures approximately 22 kilometers (14 miles) in diameter. It was named after the flowering plant Orchis.^[3]

1080 Orchis

Modelled shape of Orchis from its lightcurve
Discovery[1]
Discovered by	K. Reinmuth
Discovery site	Heidelberg Obs.
Discovery date	30 August 1927
Designations
MPC designation	(1080) Orchis
Pronunciation	/ˈɔːrkɪs/[2]
Named after	Orchis (flowering plant)[3]
Alternative designations	1927 QB · 1955 DT A906 BH
Minor planet category	main-belt · (inner)[4] background[5]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	111.76 yr (40,821 days)
Aphelion	3.0452 AU
Perihelion	1.7924 AU
Semi-major axis	2.4188 AU
Eccentricity	0.2590
Orbital period (sidereal)	3.76 yr (1,374 days)
Mean anomaly	278.54°
Mean motion	0° 15m 43.2s / day
Inclination	4.5873°
Longitude of ascending node	2.0437°
Argument of perihelion	57.028°
Physical characteristics
Mean diameter	20.755±8.470 km[6] 21.797±0.130 km[7] 21.86±0.26 km[8] 22.918±0.241 km[9] 23.28±1.7 km[4][10] 23.53±6.59 km[11] 24.62±6.75 km[12]
Synodic rotation period	16.061±0.004 h[13] 16.0657±0.0005 h[14] 16.075±0.0207 h[15] 16.1±0.1 h[16]
Pole ecliptic latitude	(255.0°, 27.0°) (λ1/β1)[17] (71.0°, 28.0°) (λ2/β2)[17]
Geometric albedo	0.029±0.002[7] 0.03±0.02[11] 0.031±0.032[12] 0.0331±0.0028[9] 0.0430±0.007[4][10] 0.0508±0.0499[6] 0.051±0.001[8]
Spectral type	Tholen = F[1][4] B–V = 0.624[1] U–B = 0.206[1]
Absolute magnitude (H)	12.133±0.002 (R)[15] · 12.20[1][4][8][9][10][11] · 12.32[6] · 12.43[12]

Orbit and classification

Orchis is a non-family asteroid of the main belt's background population.^[5] It orbits the Sun in the inner asteroid belt at a distance of 1.8–3.0 AU once every 3 years and 9 months (1,374 days; semi-major axis of 2.42 AU). Its orbit has an eccentricity of 0.26 and an inclination of 5° with respect to the ecliptic.^[1] The asteroid was first observed as A906 BH at Heidelberg in January 1906. The body's observation arc begins with its official discovery observation in August 1927.^[18]

Naming

This minor planet was named after the flowering plant Orchis, a genus in the orchid family. The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 102).^[3]

Reinmuth's flowers

Due to his many discoveries, Karl Reinmuth submitted a large list of 66 newly named asteroids in the early 1930s. The list covered his discoveries with numbers between (1009) and (1200). This list also contained a sequence of 28 asteroids, starting with 1054 Forsytia, that were all named after plants, in particular flowering plants (also see list of minor planets named after animals and plants).^[19]

Physical characteristics

In the Tholen classification, Orchis is an uncommon F-type asteroid, a type which belongs to the wider C-complex of carbonaceous asteroids.^[1][4]

Rotation period and poles

In 2010, three rotational lightcurves of Orchis were obtained from photometric observations. Lightcurve analysis gave a rotation period of 16.061, 16.075 and 16.1 hours with a brightness amplitude of between 0.23 and 0.31 magnitude (U=2+/2/3).^[13][15][16] A modeled lightcurve based on optical data from a large collaboration network found a concurring period of 16.0657 hours and two spin axis of (255.0°, 27.0°) and (71.0°, 28.0°) in ecliptic coordinates (λ, β).^[14]

Diameter and albedo

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, Orchis measures between 20.755 and 24.62 kilometers in diameter and its surface has an albedo between 0.029 and 0.051.^{[6][7][8][9][10][11][12]} The Collaborative Asteroid Lightcurve Link adopts the results obtained by IRAS, that is, an albedo of 0.0430 and a diameter of 23.28 kilometers based on an absolute magnitude of 12.2.^[4][10]