986 Amelia

{{Short description|Large background asteroid}}

{{Use dmy dates|date=July 2018}}

{{Infobox planet

| minorplanet = yes

| name = 986 Amelia

| background = #D6D6D6

| image = 000986-asteroid shape model (986) Amelia.png

| image_scale =

| caption = Modelled shape of Amelia from its lightcurve

| discovery_ref =

| discoverer = J. Comas Solà

| discovery_site = Fabra Obs.

| discovered = 19 October 1922

| mpc_name = (986) Amelia

| alt_names = A922 UA{{·}}1922 MQ
1935 BK{{·}}1966 VA
A915 JC

| pronounced =

| named_after = Amelia Solà
{{small|(discoverer's wife)}}

| mp_category = main-belt{{·}}{{small|(outer)}}
background

| orbit_ref =

| epoch = 31 May 2020 (JD 2459000.5)

| uncertainty = 0

| observation_arc = 93.64 yr (34,203 d)

| aphelion = 3.7674 AU

| perihelion = 2.4961 AU

| semimajor = 3.1317 AU

| eccentricity = 0.2030

| period = 5.54 yr (2,024 d)

| mean_anomaly = 210.80°

| mean_motion = {{Deg2DMS|0.1778|sup=ms}} / day

| inclination = 14.815°

| asc_node = 92.601°

| arg_peri = 265.52°

| mean_diameter = {{plainlist|

  • {{val|48.677|0.159|ul=km}}
  • {{val|50.94|1.2|u=km}}
  • {{val|52.30|0.78|u=km}}}}

| rotation = {{val|9.52|0.01|ul=h}}{{efn|name=lightcurve-plot-Koff}}

| pole_ecliptic_lat= {{plainlist|

  • (80.0°, 30.0°) (λ11)
  • {{nowrap|(282.0°, 30.0°) (λ22)}}}}

| albedo = {{plainlist|

  • {{val|0.113|0.004}}
  • {{val|0.1183|0.006}}
  • {{val|0.218|0.024}}}}

| spectral_type = {{plainlist|

| abs_magnitude = 9.4

}}

986 Amelia (prov. designation: {{mp|A922 UA}} or {{mp|1922 MQ}}) is a large background asteroid from the outer regions of the asteroid belt, approximately {{convert|50|km|mi|abbr=off|sigfig=2|sp=us}} in diameter. It was discovered on 19 October 1922, by Spanish astronomer Josep Comas i Solà at the Fabra Observatory in Barcelona. The L/D-type asteroid has a rotation period of 9.5 hours.{{efn|name=lightcurve-plot-Koff}} It was named after the discoverer's wife, Amelia Solà.

Orbit and classification

Amelia is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. It orbits the Sun in the outer asteroid belt at a distance of 2.5–3.8 AU once every 5 years and 6 months (2,024 days; semi-major axis of 3.13 AU). Its orbit has an eccentricity of 0.20 and an inclination of 15° with respect to the ecliptic.

On 12 May 2015, Amelia was first observed as {{mp|A915 JC}} ({{mp|1915 JC}}) at the Simeiz Observatory on the Crimean peninsula. The body's observation arc begins at the Algiers Observatory in May 1926, more than 3 years after to its official discovery observation at the Fabra Observatory.

Naming

This minor planet was named after Amelia Solà, wife of the discoverer Josep Comas i Solà (1868–1937). The official {{MoMP|986|naming citation}} was mentioned in The Names of the Minor Planets by Paul Herget in 1955 ({{small|H 94}}).

Physical characteristics

In both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), Amelia is a T-type asteroid, while in the SDSS-based taxonomy, the asteroid has been classified as an L-type.

= Rotation period and poles =

In October 2000, a rotational lightcurve of Amelia was obtained from photometric observations by American amateur astronomer Robert A. Koff at the Thornton Observatory {{Obscode|713}} in Colorado. Lightcurve analysis gave a well-defined rotation period of {{val|9.52|0.01}} hours with a brightness amplitude of {{val|0.43|0.03}} magnitude ({{small|U=3}}).{{efn|name=lightcurve-plot-Koff}}

In December 2006, a concurring period determination of {{convert|0.396533|d|h|abbr=off|order=flip|sigfig=4}} was made by astronomers Raymond Poncy, Enric Forné, Hiromi Hamanowa, Hiroko Hamanowa and Hilari Pallarés ({{small|U=3}}). In 2016, a modeled lightcurves using photometric data from various sources, rendered a concurring sidereal period of {{val|9.51856|0.00005|u=h}} and two spin axes of (80.0°, 30.0°) and (282.0°, 30.0°) in ecliptic coordinates.

= Diameter and albedo =

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, Amelia measures {{val|48.677|0.159}}, {{val|50.94|1.2}} and {{val|52.30|0.78}} kilometers in diameter and its surface has an albedo of {{val|0.218|0.024}}, {{val|0.1183|0.006}} and {{val|0.113|0.004}}, respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.1183 and a diameter of 50.94 kilometers based on an absolute magnitude of 9.4. An asteroid occultation, observed on 2 November 2006, gave a best-fit ellipse dimension of 51.0 × 51.0 kilometers. These timed observations are taken when the asteroid passes in front of a distant star. However the quality of the measurement is rated poorly.

Notes

{{notelist|refs=

{{efn|name=lightcurve-plot-Koff|1=[http://www.antelopehillsobservatory.org/lightcurves/986.gif Lightcurve plot of (986) Amelia] by Robert A. Koff (Oct 2000). Rotation period 9.52 hours with a brightness amplitude of {{val|0.43}} mag. LCDB quality code of 3. Summary figures and more information at [http://www.antelopehillsobservatory.org/index_files/Page334.htm Bob Koff's website] and at the [http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=986 LCDB].}}

}}

References

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|last146 = Scholz |first146 = A.

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