(9928) 1981 WE9

File:AnimatedOrbitOf99281981WE9.gif and Jupiter]]

The stony S-type asteroid is a member of the Flora family, one of the largest groups of asteroids in the main-belt. It orbits the Sun at a distance of 1.8–2.6 AU once every 3 years and 4 months (1,206 days).

Its orbit has an eccentricity of 0.18 and an inclination of 3° with respect to the ecliptic. A first precovery was taken at Palomar in 1951, extending the body's observation arc by 30 years prior to its official discovery observation at Bickley.

In December 2014, astronomer Maurice Clark obtained a rotational lightcurve from photometric observations at Preston Gott Observatory. Lightcurve analysis gave an ambiguous rotation period of 18.3980 hours with a brightness variation of 0.41 magnitude, suggesting a non-spheroidal shape ({{small|U=2+}}). The alternative period solution is 9.14 hours with an amplitude of 0.32 magnitude. The results supersede a previously obtained period of 5.547 hours ({{small|U=2}}).

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, the asteroid measures between 2.44 and 3.00 kilometers in diameter, and its surface has an albedo between 0.283 and 0.428. The Collaborative Asteroid Lightcurve Link assumes an intermediate albedo of 0.24 – derived from 8 Flora, the largest member and namesake of this asteroid family – and calculates a diameter of 3.11 kilometers with an absolute magnitude of 14.7.

This minor planet was numbered by the Minor Planet Center on 2 February 1999. As of 2018, it has not been named.

{{reflist|30em|refs=

{{cite web

|type = 2017-05-05 last obs.

|title = JPL Small-Body Database Browser: 9928 (1981 WE9)

|url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2009928

|publisher = Jet Propulsion Laboratory

|accessdate = 26 May 2017}}

{{cite web

|title = 9928 (1981 WE9)

|work = Minor Planet Center

|url = https://www.minorplanetcenter.net/db_search/show_object?object_id=9928

|accessdate = 17 March 2017}}

{{cite web

|title = MPC/MPO/MPS Archive

|work = Minor Planet Center

|url = https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html

|accessdate = 24 February 2018}}

{{cite web

|title = LCDB Data for (9928)

|publisher = Asteroid Lightcurve Database (LCDB)

|url = http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=9928%7C

|accessdate = 17 March 2017}}

{{cite journal

|display-authors = 6

|first1 = A. |last1 = Mainzer

|first2 = T. |last2 = Grav

|first3 = J. |last3 = Masiero

|first4 = E. |last4 = Hand

|first5 = J. |last5 = Bauer

|first6 = D. |last6 = Tholen

|first7 = R. S. |last7 = McMillan

|first8 = T. |last8 = Spahr

|first9 = R. M. |last9 = Cutri

|first10 = E. |last10 = Wright

|first11 = J. |last11 = Watkins

|first12 = W. |last12 = Mo

|first13 = C. |last13 = Maleszewski

|date = November 2011

|title = NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results

|journal = The Astrophysical Journal

|volume = 741

|issue = 2

|page = 25

|bibcode = 2011ApJ...741...90M

|doi = 10.1088/0004-637X/741/2/90

|arxiv = 1109.6407

}}

{{cite journal

|display-authors = 6

|first1 = Joseph R. |last1 = Masiero

|first2 = A. K. |last2 = Mainzer

|first3 = T. |last3 = Grav

|first4 = J. M. |last4 = Bauer

|first5 = R. M. |last5 = Cutri

|first6 = C. |last6 = Nugent

|first7 = M. S. |last7 = Cabrera

|date = November 2012

|title = Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids

|journal = The Astrophysical Journal Letters

|volume = 759

|issue = 1

|page = 5

|bibcode = 2012ApJ...759L...8M

|doi = 10.1088/2041-8205/759/1/L8

|arxiv = 1209.5794

}}

{{cite journal

|display-authors = 6

|first1 = C. R. |last1 = Nugent

|first2 = A. |last2 = Mainzer

|first3 = J. |last3 = Masiero

|first4 = J. |last4 = Bauer

|first5 = R. M. |last5 = Cutri

|first6 = T. |last6 = Grav

|first7 = E. |last7 = Kramer

|first8 = S. |last8 = Sonnett

|first9 = R. |last9 = Stevenson

|first10 = E. L. |last10 = Wright

|date = December 2015

|title = NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos

|journal = The Astrophysical Journal

|volume = 814

|issue = 2

|page = 13

|bibcode = 2015ApJ...814..117N

|doi = 10.1088/0004-637X/814/2/117

|arxiv = 1509.02522

}}

{{Cite journal

|author = Clark, Maurice

|date = June 2008

|title = Asteroid Lightcurves from the Chiro Observatory

|journal = The Minor Planet Bulletin

|volume = 35

|issue = 2

|pages = 42–43

|issn = 1052-8091

|bibcode = 2008MPBu...35...42C

}}

{{Cite journal

|author = Clark, Maurice

|date = July 2015

|title = Asteroid Photometry from the Preston Gott Observatory

|journal = The Minor Planet Bulletin

|volume = 42

|issue = 3

|pages = 163–166

|issn = 1052-8091

|bibcode = 2015MPBu...42..163C

}}

}}

• [http://www.minorplanet.info/PHP/lcdbsummaryquery.php Asteroid Lightcurve Database (LCDB)], query form ([http://www.minorplanet.info/lightcurvedatabase.html info] {{Webarchive|url=https://web.archive.org/web/20171216050541/http://www.minorplanet.info/lightcurvedatabase.html |date=2017-12-16 }})
• [https://books.google.com/books?id=aeAg1X7afOoC&pg Dictionary of Minor Planet Names], Google books
• [http://obswww.unige.ch/~behrend/page_cou.html Asteroids and comets rotation curves, CdR] – Observatoire de Genève, Raoul Behrend
• [https://www.minorplanetcenter.net/iau/lists/NumberedMPs005001.html Discovery Circumstances: Numbered Minor Planets (5001)-(10000)] – Minor Planet Center
• {{JPL small body|title=9928 (1981 WE9)|id=2009928}}

{{Minor planets navigator|9927 Tyutchev|number=9928 |PageName={{mp|(9928) 1981 WE|9}} |9929 McConnell}}

{{Small Solar System bodies}}

{{Authority control}}

{{DEFAULTSORT:1981 WE9}}

009928

009928

19811116