View source for 12923 Zephyr

{{Use dmy dates|date=October 2019}}
{{Infobox planet
 | minorplanet     = yes
 | name            = 12923 Zephyr
 | background      = #FFC2E0
 | image           = 
 | image_size      = 
 | caption         = 
 | discovery_ref   = <ref name="jpldata" />
 | discoverer      = [[Lowell Observatory Near-Earth Object Search|LONEOS]]
 | discovery_site  = [[Anderson Mesa Station|Anderson Mesa Stn.]]
 | discovered      = 11 April 1999
 | mpc_name        = (12923) Zephyr
 | alt_names       = {{mp|1999 GK|4}}
 | pronounced      = {{IPAc-en|'|z|ɛ|f|ər}}<ref>{{OED|zephyr}}</ref>
 | named_after     = [[Zephyrus]]<ref name="springer" /><br />{{small|([[Greek mythology]])}}
 | mp_category     = {{Hlist
  | [[Near-Earth object|NEO]]
  | [[Apollo asteroid|Apollo]]<ref name="jpldata" /><ref name="MPC-object" />
  | [[Potentially hazardous object|PHA]]<ref name="jpldata" /><ref name="MPC-object" />
  }}
 | orbit_ref       = <ref name="jpldata" />
 | epoch           = 4 September 2017 ([[Julian day|JD]]&nbsp;2458000.5)
 | uncertainty     = 0
 | observation_arc = 61.75&nbsp;yr (22,554 days)
 | earliest_precovery_date = 21 April 1955
 | aphelion        = 2.9267&nbsp;[[Astronomical unit|AU]]
 | perihelion      = 0.9964&nbsp;AU
 | semimajor       = 1.9615&nbsp;AU
 | eccentricity    = 0.4920
 | period          = 2.75&nbsp;[[Julian year (astronomy)|yr]] (1,003 days)
 | mean_anomaly    = 199.23[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.3588|sup=ms}} / day
 | inclination     = 5.3045°
 | asc_node        = 168.21°
 | arg_peri        = 147.06°
 | moid            = 0.0211&nbsp;AU (8.2&nbsp;[[Lunar distance (astronomy)|LD]])
 | mean_diameter   = {{Ubl
  | {{val|1.86|0.46|u=km}}<ref name="Harris-2011" />
  | {{val|2.060|0.013|u=km}}<ref name="Mainzer-2011" /><ref name="WISE" />
  | {{val|2.062|u=km}}<ref name="Pravec-2012b" />
  }}
 | rotation        = {{val|3.891|ul=h}}{{efn|name=LCDB-Pravec-1999}}
 | albedo          = {{Ubl
  | {{val|0.1764}}<ref name="Pravec-2012b" />
  | {{val|0.199|0.034}}<ref name="Mainzer-2011" /><ref name="WISE" />
  | {{val|0.20|0.16}}<ref name="Thomas-2011b" />
  | {{val|0.21|0.17}}<ref name="Harris-2011" />
  }}
 | spectral_type   = {{Hlist
  | [[SMASS classification|SMASS]] {{=}} S:<ref name="jpldata" />
  | [[S-type asteroid|S]]<ref name="Thomas-2014" /><ref name="lcdb" />
  }}
 | abs_magnitude   = {{Ubl
  | {{val|15.40|0.1}} {{small|(R)}}{{efn|name=LCDB-Pravec-1999}}
  | {{val|15.77|0.24}}<ref name="Veres-2015" />
  | 15.8<ref name="jpldata" /><ref name="WISE" />
  | {{val|15.93|0.078}}<ref name="Pravec-2012b" /><ref name="lcdb" />
  }}
}}

'''12923 Zephyr''' (''[[Minor planet provisional designation|prov. designation]]:'' {{mp|1999 GK|4}}) is a stony [[asteroid]], classified as [[potentially hazardous asteroid]] and [[near-Earth object]] of the [[Apollo asteroid|Apollo group]], approximately {{convert|2|km|mi|abbr=off|sigfig=2|sp=us}} in diameter. It was discovered on 11 April 1999, by astronomers of the [[Lowell Observatory Near-Earth Object Search]] at [[Anderson Mesa Station]] near Flagstaff, Arizona.<ref name="MPC-object" /> The asteroid was named after the deity [[Zephyrus]] from Greek mythology.<ref name="springer" />

== Orbit and classification ==

''Zephyr'' orbits the Sun at a distance of 1.0–2.9&nbsp;[[Astronomical unit|AU]] once every 2 years and 9 months (1,003 days). Its orbit has an [[orbital eccentricity|eccentricity]] of 0.49 and an [[orbital inclination|inclination]] of 5[[Degree (angle)|°]] with respect to the [[ecliptic]].<ref name="jpldata" /> The body's [[observation arc]] begins with a [[precovery]] taken at [[Palomar Observatory]] in April 1955, almost 44 years prior to its official discovery observation at Anderson Mesa.<ref name="MPC-object" />

=== Close encounters ===

This [[near-Earth asteroid]] has an Earth [[minimum orbital intersection distance]] of {{convert |0.0211 |AU |km |abbr=on |lk=off |sigfig=3}}, which corresponds to 8.2 [[Lunar distance (astronomy)|lunar distances]].<ref name="jpldata" /> This short distance as well as its sufficiently large size makes it a [[potentially hazardous asteroid]]. In September 2010, the asteroid approached Earth at {{convert |0.2546 |AU |km |abbr=on |lk=off |sigfig=3}}; it will make close encounters with Earth again in 2021, 2032 and 2043.<ref name="jpldata" />

== Naming ==

This [[minor planet]] was named after the god of the west wind, [[Zephyrus]], from [[Greek mythology]]. The name was suggested by M. Smitherman.<ref name="springer" /> The official naming citation was published by the [[Minor Planet Center]] on 28 September 2004 ({{small|[[Minor Planet Circulars|M.P.C.]] 52768}}).<ref name="MPC-Circulars-Archive" />

== Physical characteristics ==

In the [[SMASS classification]], ''Zephyr'' is a common [[S-type asteroid]].<ref name="jpldata" /> The body is also characterized as a stony asteroid by the [[Infrared Telescope Facility]],<ref name="Thomas-2014" /> and in the [[Tholen classification]] (noisy spectrum).<ref name="lcdb" />

=== Rotation period ===

In April 1999, a rotational [[lightcurve]] of ''Zephyr'' was obtained from photometric observations by Czech astronomer [[Petr Pravec]] at [[Ondřejov Observatory]]. Lightcurve analysis gave a well-defined [[rotation period]] of 3.891 hours with a brightness amplitude of 0.18 [[Magnitude (astronomy)|magnitude]] ({{small|[[LCDB quality code|U=3]]}}).{{efn|name=LCDB-Pravec-1999}}

=== Diameter and albedo ===

According to the survey carried out by the [[NEOWISE]] mission of NASA's [[Wide-field Infrared Survey Explorer]] and the ExploreNEOs survey of the [[Spitzer Space Telescope]], ''Zephyr'' measures between 1.86 and 2.062 kilometers in diameter and its surface has an [[astronomical albedo|albedo]] between 0.1764 and 0.21.<ref name="Harris-2011" /><ref name="Mainzer-2011" /><ref name="WISE" /><ref name="Pravec-2012b" /><ref name="Thomas-2011b" />

The ''Collaborative Asteroid Lightcurve Link'' adopts Petr Pravec's revised WISE data, with albedo of 0.1764 and a diameter of 2.06 kilometers based on an [[absolute magnitude]] of 15.93.<ref name="lcdb" />

== Notes ==
{{notelist|refs=

{{efn|name=LCDB-Pravec-1999|1=Pravec (1999) web: rotation period {{val|3.891}} hours with a brightness amplitude of {{val|0.18}} mag. Summary figures for (12923) Zephyr at [http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=12923%7CZephyr LCDB] and [http://www.asu.cas.cz/~ppravec/neo.htm Ondrejov Asteroid Photometry Project] ([http://www.asu.cas.cz/~ppravec/newres.txt data sheet])}}

}} <!-- end of notelist -->

== References ==
{{reflist|30em|refs=

<ref name="jpldata">{{cite web
  |type       = 2017-01-19 last obs.
  |title      = JPL Small-Body Database Browser: 12923 Zephyr (1999 GK4)
  |url        = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2012923
  |publisher  = [[Jet Propulsion Laboratory]]
  |accessdate = 17 October 2017}}</ref>

<ref name="springer">{{cite book
  |title      = Dictionary of Minor Planet Names – (12923) Zephyr, Addendum to Fifth Edition: 2003–2005
  |last       = Schmadel | first = Lutz D.
  |publisher  = [[Springer Berlin Heidelberg]]
  |page       = 76
  |date       = 2006
  |isbn       = 978-3-540-34361-5
  |doi       = 10.1007/978-3-540-34361-5_734 |chapter       = (12923) Zephyr [1.96, 0.49, 5.3] }}</ref>

<ref name="MPC-object">{{cite web
  |title      = 12923 Zephyr (1999 GK4)
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/db_search/show_object?object_id=12923
  |accessdate = 17 October 2017}}</ref>

<ref name="MPC-Circulars-Archive">{{cite web
  |title      = MPC/MPO/MPS Archive
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html
  |accessdate = 17 October 2017}}</ref>

<ref name="Mainzer-2011">{{cite journal
  |display-authors = 6
  |first1     = A. |last1 = Mainzer
  |first2     = T. |last2 = Grav
  |first3     = J. |last3 = Bauer
  |first4     = J. |last4 = Masiero
  |first5     = R. S. |last5 = McMillan
  |first6     = R. M. |last6 = Cutri
  |first7     = R. |last7 = Walker
  |first8     = E. |last8 = Wright
  |first9     = P. |last9 = Eisenhardt
  |first10    = D. J. |last10 = Tholen
  |first11    = T. |last11 = Spahr
  |first12    = R. |last12 = Jedicke
  |first13    = L. |last13 = Denneau
  |first14    = E. |last14 = DeBaun
  |first15    = D. |last15 = Elsbury
  |first16    = T. |last16 = Gautier
  |first17    = S. |last17 = Gomillion
  |first18    = E. |last18 = Hand
  |first19    = W. |last19 = Mo
  |first20    = J. |last20 = Watkins
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  |first22    = G. L. |last22 = Bryngelson
  |first23    = A. |last23 = Del Pino Molina
  |first24    = S. |last24 = Desai
  |first25    = M. |last25 = Gómez Camus
  |first26    = S. L. |last26 = Hidalgo
  |first27    = I. |last27 = Konstantopoulos
  |first28    = J. A. |last28 = Larsen
  |first29    = C. |last29 = Maleszewski
  |first30    = M. A. |last30 = Malkan
  |first31    = J.-C. |last31 = Mauduit
  |first32    = B. L. |last32 = Mullan
  |first33    = E. W. |last33 = Olszewski
  |first34    = J. |last34 = Pforr
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  |first36    = J. V. |last36 = Scotti
  |first37    = L. H. |last37 = Wasserman
  |date       = December 2011
  |title      = NEOWISE Observations of Near-Earth Objects: Preliminary Results
  |journal    = The Astrophysical Journal
  |volume     = 743
  |issue      = 2
  |page       = 17
  |bibcode    = 2011ApJ...743..156M
  |doi        = 10.1088/0004-637X/743/2/156
  |arxiv      = 1109.6400}}</ref>

<ref name="lcdb">{{cite web
  |title      = LCDB Data for (12923) Zephyr
  |publisher  = Asteroid Lightcurve Database (LCDB)
  |url        = http://www.minorplanet.info/PHP/generateOneAsteroidInfo.php?AstInfo=12923%7CZephyr
  |accessdate = 17 October 2017}}</ref>

<ref name="Harris-2011">{{Cite journal
  |display-authors = 6
  |first1     = A. W. |last1 = Harris
  |first2     = M. |last2 = Mommert
  |first3     = J. L. |last3 = Hora
  |first4     = M. |last4 = Mueller
  |first5     = D. E. |last5 = Trilling
  |first6     = B. |last6 = Bhattacharya
  |first7     = W. F. |last7 = Bottke
  |first8     = S. |last8 = Chesley
  |first9     = M. |last9 = Delbo
  |first10    = J. P. |last10 = Emery
  |first11    = G. |last11 = Fazio
  |first12    = A. |last12 = Mainzer
  |first13    = B. |last13 = Penprase
  |first14    = H. A. |last14 = Smith
  |first15    = T. B. |last15 = Spahr
  |first16    = J. A. |last16 = Stansberry
  |first17    = C. A. |last17 = Thomas
  |date       = March 2011
  |title      = ExploreNEOs. II. The Accuracy of the Warm Spitzer Near-Earth Object Survey
  |journal    = The Astronomical Journal
  |volume     = 141
  |issue      = 3
  |page       = 10
  |bibcode    = 2011AJ....141...75H
  |doi        = 10.1088/0004-6256/141/3/75|url = https://authors.library.caltech.edu/22857/1/Harris2011p13012Astron_J.pdf }}</ref>

<ref name="Pravec-2012b">{{Cite journal
  |first1     = Petr |last1 = Pravec
  |first2     = Alan W. |last2 = Harris
  |first3     = Peter |last3 = Kusnirák
  |first4     = Adrián |last4 = Galád
  |first5     = Kamil |last5 = Hornoch
  |date       = September 2012
  |title      = Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations
  |journal    = Icarus
  |volume     = 221
  |issue      = 1
  |pages      = 365–387
  |bibcode    = 2012Icar..221..365P
  |doi        = 10.1016/j.icarus.2012.07.026}}</ref>

<ref name="WISE">{{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}}</ref>

<ref name="Thomas-2011b">{{Cite journal
  |display-authors = 6
  |first1     = C. A. |last1 = Thomas
  |first2     = D. E. |last2 = Trilling
  |first3     = J. P. |last3 = Emery
  |first4     = M. |last4 = Mueller
  |first5     = J. L. |last5 = Hora
  |first6     = L. A. M. |last6 = Benner
  |first7     = B. |last7 = Bhattacharya
  |first8     = W. F. |last8 = Bottke
  |first9     = S. |last9 = Chesley
  |first10    = M. |last10 = Delbó
  |first11    = G. |last11 = Fazio
  |first12    = A. W. |last12 = Harris
  |first13    = A. |last13 = Mainzer
  |first14    = M. |last14 = Mommert
  |first15    = A. |last15 = Morbidelli
  |first16    = B. |last16 = Penprase
  |first17    = H. A. |last17 = Smith
  |first18    = T. B. |last18 = Spahr
  |first19    = J. A. |last19 = Stansberry
  |date       = September 2011
  |title      = ExploreNEOs. V. Average Albedo by Taxonomic Complex in the Near-Earth Asteroid Population
  |journal    = The Astronomical Journal
  |volume     = 142
  |issue      = 3
  |page       = 12
  |bibcode    = 2011AJ....142...85T
  |doi        = 10.1088/0004-6256/142/3/85|doi-access= free
  }}</ref>

<ref name="Thomas-2014">{{cite journal
  |first1     = Cristina A. |last1 = Thomas
  |first2     = Joshua P. |last2 = Emery
  |first3     = David E. |last3 = Trilling
  |first4     = Marco |last4 = Delbó
  |first5     = Joseph L. |last5 = Hora
  |first6     = Michael |last6 = Mueller
  |date       = January 2014
  |title      = Physical characterization of Warm Spitzer-observed near-Earth objects
  |journal    = Icarus
  |volume     = 228
  |pages      = 217–246
  |bibcode    = 2014Icar..228..217T
  |doi        = 10.1016/j.icarus.2013.10.004
  |arxiv      = 1310.2000}}</ref>

<ref name="Veres-2015">{{cite journal
  |display-authors = 6
  |first1     = Peter |last1 = Veres
  |first2     = Robert |last2 = Jedicke
  |first3     = Alan |last3 = Fitzsimmons
  |first4     = Larry |last4 = Denneau
  |first5     = Mikael |last5 = Granvik
  |first6     = Bryce |last6 = Bolin
  |first7     = Serge |last7 = Chastel
  |first8     = Richard J. |last8 = Wainscoat
  |first9     = William S. |last9 = Burgett
  |first10    = Kenneth C. |last10 = Chambers
  |first11    = Heather |last11 = Flewelling
  |first12    = Nick |last12 = Kaiser
  |first13    = Eugen A. |last13 = Magnier
  |first14    = Jeff S. |last14 = Morgan
  |first15    = Paul A. |last15 = Price
  |first16    = John L. |last16 = Tonry
  |first17    = Christopher |last17 = Waters
  |date       = November 2015
  |title      = Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1{{Snd}} Preliminary results
  |journal    = Icarus
  |volume     = 261
  |pages      = 34–47
  |bibcode    = 2015Icar..261...34V
  |doi        = 10.1016/j.icarus.2015.08.007
  |arxiv      = 1506.00762}}</ref>

}} <!-- end of reflist -->

== External links ==
* [https://newton.spacedys.com/neodys/index.php?pc=1.1.0&n=12923 (12923) Zephyr] at NEODyS-2
* [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=16 December 2017 }})
* [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]{{Snd}} Observatoire de Genève, Raoul Behrend
* {{NeoDys|12923}}
* {{ESA-SSA|12923|Zephyr}}
* {{JPL small body}}

{{Minor planets navigator |(12922) 1998 WW19 |number=12923 | }}
{{Small Solar System bodies}}
{{Authority control}}

{{DEFAULTSORT:Zephyr}}
[[Category:Apollo asteroids|012923]]
[[Category:Discoveries by LONEOS|012923]]
[[Category:Named minor planets]]
[[Category:Earth-crossing asteroids]]
[[Category:Potentially hazardous asteroids|012923]]
[[Category:Astronomical objects discovered in 1999|19990411]]